International Association of Hydrological Scienceshydrologie.org/redbooks/a271/P271...

International Association of Hydrological Sciences The Extremes

of the Extremes:

Extraordinary Floods edited by Árni Snorasson, Helga P. Finnsdóttir & Marshall E. Moss

IAHS Publication no. 271 (published March 2002) in the IAHS Series of Proceedings and ReportsISBN 1-901502-66-X; 394 + xiv pp.; price £60.00

Extreme floods are among the most destructive forces of nature; there is a perception that they are occurring with higher frequency now than in the past. This is a cause for international concern and calls for an understanding of the circumstances that might generate such disastrous events.

This was the motive for the Reykjavík symposium on extraordinary floods, the Extremes of the Extremes, co-convened by the International Association of Hydrological Sciences (IAHS) and the Hydrological Service in Iceland; this publication is an outcome of that meeting.

The main focus of the papers included in this volume is the geophysical processes related to floods, but the statistical and mathematical aspects of flood analysis and forecasting are also addressed, and the issues of flooding and flood abatement are put into economic, social and ethical perspective. The 60 papers in this volume have been grouped under the following themes:– Physical processes related to floods interplay of snow and ice with rain and

temperature— intense mountain precipitation in semiarid areas—glacial outburst floods—volcanic activity and the flood at Vatnajökull Glacier, Iceland, 1996

– Prehistoric and historic floods catastrophic floods in Iceland—floods during the North American glaciation—extreme floods on Mars

– Floods: case studies from around the world, from the Himalayas to the Mediterranean to Norway

– Geomorphological and environmental questions related to floods focusing on glacial floods

– Statistical analysis and forecasting of floods extreme value analysis—multivariate considerations—forecasting: theoretical and methodological viewpoints—practicalities of forecasting and flood zone mapping—climate variability and change

– Predictability and abatement of floods the fundamental nature of extreme events—how society does and should deal with the threat of flood hazards

Contents

Preface by Árni Snorrason, Helga P. Finnsdóttir & Marshall Moss v

1 Physical Processes Related to Floods

Facing a changeable hydrological regime in a Mediterranean country Giuseppe Batini & Marcello Benedini 3

Extreme ice jam floods along the Saint John River, New Brunswick, Canada Spyros Beltaos & Brian C. Burrell 9

Maximum rainfall in Poland—a design approach Ewa Bogdanowicz & Juliusz Stachý 15

Catastrophic flooding in the Czech Republic since 5 July 1997 Alois Chlebek & Milan Jařabáč 19

Influence of climate on the flood frequency distribution within a large region of southern Italy Pierluigi Claps, Mauro Fiorentino & Vito Iacobellis 25

Assessment of possible jökulhlaups from Lake Demmevatn in Norway Hallgeir Elvehøy, Rune V. Engeset, Liss M. Andreassen, Jack Kohler, Yngvar Gjessing & Helgi Björnsson 31

Simulation of the jökulhlaup on Skeiðarársandur, Iceland, in November 1996 using MIKE 21 HD Claes Eskilsson, Jón Ingvi Árnason & Dan Rosbjerg 37

The estimation of rainfall frequency in a Mediterranean environment due to extraordinary combinations of hydrological and climatic conditions Salvatore Gabriele & Paolo Villani 45

Multifractal taming of extreme hydrometeorological events Pierre Hubert, Hocine Bendjoudi, Daniel Schertzer & Shaun Lovejoy 51

The initiation of the 1996 jökulhlaup from Lake Grímsvötn, Vatnajökull, Iceland (Keynote paper) Tómas Jóhannesson 57

How often do extreme events occur? Felix Naef 65

Controls on the development of supraglacial floodwater outlets during jökulhlaups Matthew J. Roberts, Andrew J. Russell, Fiona S. Tweed & Óskar Knudsen 71

Extreme floods in mountain areas—an overview (Keynote paper) Manfred Spreafico 77

A hydroclimatic analysis of the 1997 flood at Grand Forks, North Dakota (USA) Paul E. Todhunter 87

Flood prediction in permeable drainage basins Ana Lisa Vetere Arellano, Paul Samuels & Paul Webster 93

2 Prehistoric and Historic Floods

Recent extreme floods on Mars Devon Burr & Alfred McEwen 101

Jökulhlaup deposits at the Ásbyrgi Canyon, northern Iceland: sedimentology and implications for flow type Óskar Knudsen & Andrew J. Russell 107

Evidence for province-wide water storage and catastrophic drainage beneath the Laurentide Ice Sheet, Alberta, Canada Mandy J. Munro-Stasiuk & Darren B. Sjogren 113

Catastrophic floods in Iceland Haukur Tómasson 121

3 Floods: Case Studies

The most severe floods of the Tiber River in Rome Maria Gabriella Alessandroni & Gianrenzo Remedia 129

Extraordinary summer flood in a karst area: case study in Croatia Boris Berakovic & Ksenija Cesarec 133

Recent extreme weather events in the Nepal Himalayas (Keynote paper) Suresh Raj Chalise & Narendra Raj Khanal 141

The flood of floods—Poland, summer 1997 Zbigniew W. Kundzewicz 147

Historic extreme floods as input to dam safety analyses Grethe Holm Midttømme & Jens Kristian Tingvold 155

A study of extreme storm events in the Greater Athens area, Greece Maria Mimikou, Evangelos Baltas & Ekaterini Varanou 161

Highest floods in India P. R. Rakhecha 167

The large flood of 1860 in Norway Lars Andreas Roald 173

A stochastic model for exploring extreme flood events in the UK Harvey J. E. Rodda, Agnete Berger & Robert Muir-Wood 179

4 Geomorphological and Environmental Questions Related to Floods

Relative roles of geomorphology and water input distribution in an extreme flood structure Christophe Cudennec, Frederic Gogien, Jacques Bourges, Jean Duchesne & Ridha Kallel 187

Surge-related floods at Skeiðarárjökull Glacier, Iceland: implications for ice-marginal outwash deposits Thaiënne A. G. P. Van Dijk & Oddur Sigurðsson 193

Real-time monitoring of glacial rivers in Iceland Sverrir Óskar Elefsen, Árni Snorrason, Hreinn Haraldsson, Sigurður Reynir Gíslason &

Hrefna Kristmannsdóttir 199

Formation of kettle holes following a glacial outburst flood (jökulhlaup), Skeiðarársandur, southern Iceland Helen Fay 205

Characterizing the flash flood hazards potential along the Red Sea coast of Egypt Eman M. Ghoneim, Nigel W. Arnell & Giles M. Foody 211

Erosion and deposition in the proglacial zone: the 1996 jökulhlaup on Skeiðarársandur, southeast Iceland Basil Gomez, Andrew J. Russell, Laurence C. Smith & Óskar Knudsen 217

Seasonal variation in the chemistry of glacial-fed rivers in Iceland Hrefna Kristmannsdóttir, Sigurður R. Gíslason, Árni Snorrason, Hreinn Haraldsson, Steinunn Hauksdóttir & Ásgeir Gunnarsson 223

Geochemical warning for subglacial eruptions—background and history Hrefna Kristmannsdóttir, Árni Snorrason, Sigurður R. Gíslason, Hreinn Haraldsson, Ásgeir Gunnarsson, Steinunn Hauksdóttir & Sverrir Ó. Elefsen 231

Criteria for distinguishing high magnitude flood events in the proglacial fluvial sedimentary record Philip M. Marren 237

The influence of channel flood history on the impact of the November 1996 jökulhlaup, Skeiðarársandur, Iceland (Keynote paper) Andrew J. Russell & Óskar Knudsen 243

Impact of the July 1999 jökulhlaup on the proximal River Jökulsá á Sólheimasandi, Mýrdalsjökull Glacier, southern Iceland Andrew J. Russell, Fiona S. Tweed, Óskar Knudsen, Matthew J. Roberts, Timothy D. Harris & Philip M. Marren 249

5 Statistical Analysis of Floods

Dam design flood estimation based on bivariate extreme-value distributions Álvaro A. Aldama & Aldo I. Ramírez 257

Study of parameter estimation methods for Pearson-III distribution in flood frequency analysis Chen Yuanfang, Hou Yu, Pieter Van Gelder & Sha Zhigui 263

Assessment of a simplified runoff model for theoretical derivation of the probability distribution of floods Giuseppe Gioia, Vito Iacobellis & Maria Rosaria Margiotta 271

Power law distribution of catastrophic floods Carlo De Michele, Paolo La Barbera & Renzo Rosso 277

The probable maximum flood at the Ukai and Lakhwar dam sites in India P. R. Rakhecha & C. Clark 283

Estimation of extreme Pareto quantiles using upper order statistics (Keynote paper) Óli G. B. Sveinsson, Duane C. Boes & Jose D. Salas 289

A study on threshold selection in POT analysis of extreme floods

Shigenobu Tanaka & Kaoru Takara 299

6 Statistical Analysis and Forecasting

Water level forecasts for Lake Managua Kari Ahti & Luis Sandor Palacios Ruiz 307

Flood inundation maps—mapping of flood prone areas in Norway Hallvard Berg

313

Application of the stochastic self-training procedure for the modelling of extreme floods Vadim Kuzmin, Pieter van Gelder, Hafzullah Aksoy & ISmail Kucuk 317

The region of influence approach in complex and highly variable environments—experiences from Switzerland Martin Pfaundler & Paolo Burlando 323

Extreme climatic and hydrological events associated with El Niño/Southern Oscillation: analysis (1500–1999) and forecast (2000–2050) Jorge Sánchez-Sesma 329

Weighted least squares method—improved estimates when the index flood method is used with annual maximum floods (Keynote paper) Savithri Senaratne & Conleth Cunnane 333

Simulation of discharge fields Thomas Skaugen 341

Flood forecasting for the River Rhine in The Netherlands Eric Sprokkereef 347

7 The Predictability and Abatement of Floods

The world’s maximum observed floods Reg Herschy 355

Flood protection in the context of sustainable development Zbigniew W. Kundzewicz 361

What is an extreme flood and for whom? Dan Lundquist 367

Extremeness of extreme floods Ferenc Papp 373

Coping with extreme floods: warnings, impacts and response Edmund Penning-Rowsell & Sue Tapsell 379

Social and economic dimensions of the 1998 extreme floods in coastal Chiapas, Mexico Alvaro Sanchez-Crispin & Enrique Propin-Frejomil 385

Key word index 391

________________________________________________________________________The Extremes of the Extremes: Extraordinary Floods (Proceedings of a symposium held at Reykjavik, Iceland, July 2000). IAHS Publ. no. 271, 2002. pp. 3–8.

Facing a changeable hydrological regime in a Mediterranean country

GIUSEPPE BATINI & MARCELLO BENEDINIDepartment of Technical Services, Via Curtatone 3, I-00185 Rome, Italye-mail: [email protected]

Abstract Located completely within the Mediterranean basin, Italy is now facing a climatic pattern characterized by new trends. The occurrence of floods seems in particular to be more worrisome than in past years, with higher peak values and a decreased frequency. At the same time, long periods of scarce rainfall seem to favour the occurrence of droughts, which create difficulties in water resources management. The Italian Department of Technical Services, in line with its mandatory countrywide activity, has promoted ad hoc investigations to improve and update knowledge of the fundamental mechanisms governing the high precipitation and flood regime. A substantial part of the Department’s activity is in hydrological surveys for which a monitoring system, based on the most advanced technological breakthroughs, has been put into operation.Key words Mediterranean; monitoring; flood frequency; drought; precipitation characteristics


Extreme ice jam floods along the Saint John River, New Brunswick, Canada

SPYROS BELTAOSNational Water Research Institute, PO Box 5050, 867 Lakeshore Road, Burlington, Ontario L7R 4A6, Canadae-mail: [email protected]

BRIAN C. BURRELLNew Brunswick Department of the Environment, Fredericton, New Brunswick, Canada

Abstract Extreme ice jams and the resulting floods and ice runs destroy property and infrastructure, disrupt transportation, inhibit hydropower generation, affect aquatic life and habitat, and pose risks to human life. Ice jam processes are described briefly and their flooding potential explained in terms of their large aggregate thickness and roughness. The recent flood history of the Saint John River shows that the five most severe flood events during the period 1958–1999 were caused by ice jams resulting from the spring breakup of the ice cover. This is reflected in the relative frequencies of ice-jam and open-water stages, especially in the range of rare events. At present, efforts are underway to implement predictive models in flood forecasting and emergency response operations. Prompted by global warming concerns, historical hydroclimatic records have been analysed. The available evidence suggests the Saint John River is becoming subject to more frequent mid-winter jams and higher April flows, both of which augment the potential for major jamming.Key words breakup; extreme event; flood; frequency; global warming; ice jam; return period; river; water level


Maximum rainfall in Poland—a design approach

EWA BOGDANOWICZ & JULIUSZ STACHÝInstitute of Meteorology and Water Management, Podlesna 61, 01-673 Warsaw, Polande-mail: [email protected]

Abstract Heavy rainfall data are often used in engineering design of structures that control storm runoff. Series of annual maximum precipitation (1960–1990) in 14 fixed time intervals from 20 meteorological stations in Poland were used to develop a general relationship for rainfall depth, duration and frequency. Generalization of rainfall information was done by means of regional description. The regions were distinguished by using cluster analysis.Key words maximum rainfall; statistics; cluster analysis


Catastrophic flooding in the Czech Republic since 5 July 1997

ALOIS CHLEBEK & MILAN JAŘABÁČForestry and Game Management Research Institute, Nadrazni 2811, 73-801 Frýdek Místek, Czech Republice-mail: [email protected]

Abstract The Czech Republic is not often affected by natural catastrophes like floods which may be caused either by sudden rainstorms or by less intense but prolonged rainfall. Both types of floods may be associated with torrential outflows in headwaters and accelerated erosion of streambeds and banks. Such an event was experienced at the beginning of July 1997. There are an increasing number of insurance claims on the security of lives and properties. Flood defence must consist not only of engineering structures, but also the public and the state authorities must be prepared to defend themselves.Key words forest hydrology; experimental basins; catastrophic flood; flood defence


Influence of climate on the flood frequency distribution within a large region of southern Italy

PIERLUIGI CLAPS, MAURO FIORENTINODipartimento di Ingegneria e Fisica dell’Ambiente, Università della Basilicata, Contrada Macchia Romana, I-85100 Potenza, Italye-mail: [email protected]

VITO IACOBELLISDipartimento di Ingegneria delle Acque, Politecnico di Bari, via E. Orabona 4, I-70125 Bari, Italye-mail: [email protected]

Abstract In the theoretical derivation of flood frequency distribution as well as in the statistical

regional analysis, climate plays a decisive role, being closely related to values and to patterns of variability of physically consistent parameters. We focused on the average annual number of flood peaks, q, and on the ratio of q over the average annual rate of rainfall events, p, as crucial parameters of extreme value distributions based on a Poisson process of occurrences. The link between climate and these statistical parameters is first empirically analysed and then explained as to how they relate to a characteristic water loss parameter dependent on climate, namely, a dimensionless loss factor f* representing the storm rainfall threshold that determines if runoff is generated or not. Data from 20 basins in southern Italy, with hyper-humid to semiarid climates, show meaningful relationships between the degree of aridity and estimates of q/p and f*.Key words floods; climate; water losses; regional analysis; annual peaks rate; Mediterranean basins; southern Italy


Assessment of possible jökulhlaups from Lake Demmevatn in Norway

HALLGEIR ELVEHØY, RUNE V. ENGESET, LISS M. ANDREASSENNorwegian Water Resources and Energy Directorate (NVE), PO Box 5091 Majorstua, N-0301 Oslo, Norwaye-mail: [email protected]

JACK KOHLERNorwegian Polar Research Institute, Norway

YNGVAR GJESSINGGeophysical Institute, University of Bergen, Norway

HELGI BJÖRNSSON1Science Institute, University of Iceland, Iceland

Abstract Artificial drainage tunnels were constructed after repeated catastrophic jökulhlaups from the glacier-dammed Lake Demmevatn. Models of glacier change and jökulhlaup discharge were used to develop scenarios in which the rock tunnels were blocked. The results show how the maximum jökulhlaup discharge depends on the volume of water in the lake and on the drainage mechanism. The discharge depends on the thickness of the glacier and thus on its response to a possible future climate change.Key words jökulhlaup; outburst discharge model; Glacier Hardangerjøkulen; Norway


Simulation of the jökulhlaup on Skeiðarársandur, Iceland, in November 1996 using MIKE 21 HD

CLAES ESKILSSONWater Environment Transport, Chalmers University of Technology, S-41296 Göteborg, Swedene-mail: [email protected]

JÓN INGVI ÁRNASON & DAN ROSBJERG

Department of Hydrodynamics and Water Resources, Technical University of Denmark, Building 115, DK-2800 Kongens Lyngby, Denmark

Abstract The jökulhlaup (glacier outburst flood) on Skeiðarársandur was generated by a subglacial volcanic eruption beneath the Glacier Vatnajökull. On 5 November 1996, the flooding of the outwash plain started, and a total peak discharge of approximately 50 000 m3 s-1 was reached in just 16 h. In the present study a MIKE 21 HD model was set-up and calibrated for simulating the jökulhlaup. Snapshots of the inundated area, as well as measurements of maximum water levels in the upper part of the area, were used to calibrate the model. The results indicate that the discharges estimated during the event are of the correct magnitude, although the peak discharges are most likely slightly overestimated.Key words jökulhlaup; glacier outburst flood; numerical modelling; MIKE 21 HD________________________________________________________________________The Extremes of the Extremes: Extraordinary Floods (Proceedings of a symposium held at Reykjavik, Iceland, July 2000). IAHS Publ. no. 271, 2002. pp. 45–50.

The estimation of rainfall frequency in a Mediterranean environment due to extraordinary combinations of hydrological and climatic conditions

SALVATORE GABRIELE CNR-IRPI, Via Cavour, I-87036 Rende (CS), Italye-mail: [email protected]

PAOLO VILLANIDipartimento di Ingegneria Civile, Università di Parma, Italy

Abstract The application of geostatistical analysis techniques, together with robust at-site parameter estimating techniques, such as those referring to probability-weighted moments (PWM), has been applied to the whole of Italy. It seems to show that the spatial variability of the two-component extreme value (TCEV) distribution model parameters can be correlated with external variables, like the distance from the sea and from mountain barriers, the exposure of the slopes, and so on. An application of these concepts, as a case study, was carried out for all of Italy, including more than 3000 raingauge stations with at least 30 years of observation.Key words regional analysis; geostatistics; flood; rainfall; two-component extreme value distribution; Italy ________________________________________________________________________The Extremes of the Extremes: Extraordinary Floods (Proceedings of a symposium held at Reykjavik, Iceland, July 2000). IAHS Publ. no. 271, 2002. pp. 51–56.

Multifractal taming of extreme hydrometeorological events

PIERRE HUBERTUMR Sisyphe, Centre d’Informatique Géologique, Ecole des Mines de Paris, F-77305 Fontainebleau, Francee-mail: [email protected]

HOCINE BENDJOUDI UMR Sisyphe, Laboratoire de Géologie Appliquée, Université Pierre et Marie Curie, Paris, Francee-mail: [email protected]

DANIEL SCHERTZER Laboratoire de Modélisation en Mécanique, Université Pierre et Marie Curie, Paris, Francee-mail: [email protected]

SHAUN LOVEJOYPhysics Department, McGill University, Montreal, Canadae-mail: [email protected]

Abstract For hydrologists, scaling is some kind of philosopher’s stone. There exists in the literature a lot of empirical work about extreme rainfall events and floods, their mutual relationship and their dependence upon observation time-steps and/or drainage basin size. Multifractal approaches allow such studies to be viewed in a new perspective and given a rational basis. These approaches give prominence to spatial- and temporal-scale invariance of hydrometeorological processes and so permit normal and extreme events to be put in the same conceptual framework. Furthermore, multifractal approaches suggest that both rainfall and discharge extreme events, might be ruled by algebraic statistical laws, rather than by exponential ones as has been generally postulated up to now. The theoretical and practical consequences of such conjectures are highly significant, especially when taking into account hydrological risk for land-use planning or the design of water structures, as they result in much shorter return periods for so-called exceptional events than the classical approaches do.Key words extreme event; flood; rainfall; runoff; multifractal


The initiation of the 1996 jökulhlaup from Lake Grímsvötn, Vatnajökull, Iceland

TÓMAS JÓHANNESSONIcelandic Meteorological Office, Bústaðavegur 9, IS-150 Reykjavík, Icelande-mail: [email protected]

Abstract The jökulhlaup from Lake Grímsvötn in Vatnajökull Ice Cap in 1996 was initiated by a different physical mechanism to that assumed in traditional theories of jökulhlaups. The maximum discharge was reached only 16 h after the start of the flood at the terminus. Water outbursts, through a >300 m thick glacier near the terminus, indicate water pressures several bars in excess of ice overburden at the beginning of the flood. A deep ice canyon was formed in the ice cap near Lake Grímsvötn extending along about 10% of the subglacial floodpath. Frozen sediments formed in crevasses and frazil ice on the surface of the flood waters indicate the flow of supercooled water in the terminus region. These observations can be interpreted such that the jökulhlaup was initiated by the movement of a localized pressure wave that travelled 50 km in 10 h from Lake Grímsvötn to the terminus, forming a subglacial pathway along the glacier bed. Shortly after this wave reached the terminus, the jökulhlaup was flowing at a high discharge through a tunnel which would have needed much a longer time to form by ice melting as assumed in existing theories of jökulhlaups. The observations also indicate that in current theories the rate of heat transfer from subglacial flood water to the overlying ice is greatly underestimated.Key words jökulhlaup; Grímsvötn, Iceland; heat transfer; supercooling; frozen sediments


How often do extreme events occur?

FELIX NAEF

Hydromechanics and Water Resources Management, Swiss Federal Institute of Technology, CH-8093 Zurich, Switzerlande-mail: [email protected]

Abstract The estimation of return periods of extreme events can be improved by combining historical data, rainfall–runoff modelling and flood frequency analysis. Discharge records can often be extended using historic events. A better understanding of the relevant runoff formation processes helps to assess the magnitude of extreme floods. To this purpose, plots of 60 m2 with different soils and geology were exposed to artificial rains of up to 100 mm h -1 for several hours and relevant flows monitored. Based on these results, maps of areas with different reactions to precipitation were developed and used for runoff computations. Examples of combined analyses of historic events, flood frequency analysis and simulations with a model based on plots are presented.Key words extreme floods; flood frequency analysis; historical floods; runoff processes; return period; rainfall–runoff model simulation


Controls on the development of supraglacial floodwater outlets during jökulhlaups

MATTHEW J. ROBERTSDivision of Geography, Staffordshire University, College Road, Stoke-on-Trent, Staffordshire ST4 2DE, UK

ANDREW J. RUSSELLSchool of Earth Sciences and Geography, Keele University, Keele, Staffordshire ST5 5BG, UKe-mail: [email protected]

FIONA S. TWEEDDivision of Geography, Staffordshire University, College Road, Stoke-on-Trent, Staffordshire ST4 2DE, UKe-mail: [email protected]

ÓSKAR KNUDSENKlettur Consulting Engineers, Bíldshöfða 12, IS-112 Reykjavík, Iceland e-mail: [email protected]

Abstract Recent field observations have revealed that jökulhlaups with a near-instantaneous rise to peak discharge can generate temporary hydraulic pressures capable of forcing floodwater through the surface of glaciers. This paper identifies and explains the controls on the development of supraglacial jökulhlaup outlets. Field evidence is presented from two recent Icelandic jökulhlaups, which produced multiple supraglacial outbursts. Subglacial hydraulic pressure increase is identified as the principal control on supraglacial outlet development during jökulhlaups. A near-instantaneous rise to peak subglacial water pressure can produce supraglacial outbursts by hydrofracturing. Pressure increases below the hydrofracturing threshold, but above ice overburden pressure, can back-feed pre-existing drainage, resulting in outbursts from moulins and crevasses. Hydrofracture outbursts can route water to areas of the glacier not normally inundated by floods, and can control the spatial distribution of ice block release.Key words jökulhlaup; subglacial hydrology; flood routing; hydrofracturing; supraglacial; Iceland


Extreme floods in mountain areas—an overview

MANFRED SPREAFICOSwiss National Hydrological and Geological Survey, CH-3003 Berne, Switzerlande-mail: [email protected]

Abstract Some experiences, results, investigations and problems related to extreme floods in mountainous drainage basins are presented by using Switzerland as an example. Most of the topics chosen are not only valid for the specific characteristics prevailing in Switzerland, but also are generally applicable for mountainous drainage basins. In the past years considerable progress has been made in the provision of basic hydrological information. However, there are still inadequacies in the monitoring of floods, in data analysis and interpretation, and with hydrological studies and applications for alarm systems and forecasts.Key words flood monitoring; data analysis; runoff process description; comparison of models; flood events in Switzerland; Switzerland


A hydroclimatic analysis of the 1997 flood at Grand Forks, North Dakota (USA)

PAUL E. TODHUNTERDepartment of Geography, Box 9020, University of North Dakota, Grand Forks, North Dakota 58202-9020, USAe-mail: [email protected]

Abstract The flood of April 1997 at Grand Forks, North Dakota, was the most costly flood on a per capita basis for a major metropolitan area in the history of the United States, with losses totalling nearly 3.6 billion US dollars. The physical characteristics of the drainage basin that make the metropolitan area one of the most susceptible locations for extreme spring snowmelt flooding in North America are reviewed. The physical processes that control the magnitude of spring flooding in the region are summarized and their condition during the 1996–1997 flood season is described. The Grand Forks flood resulted from the major physical controls of regional flooding occurring at extreme levels throughout the basin.Key words snowmelt flooding; flood catastrophe; Red River of the North; Grand Forks, North Dakota, USA________________________________________________________________________The Extremes of the Extremes: Extraordinary Floods (Proceedings of a symposium held at Reykjavik, Iceland, July 2000). IAHS Publ. no. 271, 2002. pp. 93–98.

Flood prediction in permeable drainage basins

ANA LISA VETERE ARELLANOEuropean Commission, DG Joint Research Centre, Institute for the Protection and Security of the Citizen, Ispra, Italye-mail: [email protected]

PAUL SAMUELSHR Wallingford Ltd, Howbery Park, Wallingford, Oxfordshire OX10 8BA, UK

e-mail: [email protected]

PAUL WEBSTERHydro-logic, Old Grammar School, Church Street, Bromyard, Herefordshire HR7 4DP, UKe-mail: [email protected]

Abstract Permeable drainage basins are not generally regarded as prone to flooding. However, such drainage basins are susceptible to inundations. Existing flood frequency estimation techniques are not able to predict efficiently flood peaks and volumes on permeable drainage basins. The paper reviews analytical design guidelines and investigates the merits and limits of using groundwater head and river flow data in flood estimation for permeable drainage basins. A methodology for the identification of a critical groundwater head threshold, beyond which there is a relatively higher risk of flooding is proposed. The rock type of chalk has been chosen as the main focus of this study.Key words flooding on permeable catchments; chalk; groundwater level–river flow correlation; River Lavant, Chichester UK; River Waithe Beck, Grainsby UK


Recent extreme floods on Mars

DEVON BURRDepartment of Geosciences, University of Arizona, Gould-Simpson Building, 1040 East Fourth Street, Tucson, Arizona 85721-0077, USA; mail: 1629 East University Boulevard, Tucson, Arizona 85721, USAe-mail: [email protected]

ALFRED McEWENLunar and Planetary Laboratory, University of Arizona, 1629 East University Boulevard, Tucson, Arizona 85721, USA

Abstract New high-resolution images of the large (>20 km wide) flood channels near the Cerberus Plains and in Marte Vallis, Mars, reveal streamlined islands, longitudinal grooving, and terracing, similar to features in the Channeled Scabland (USA). These are the youngest catastrophic flood channels on Mars, formed less than 200–500 × 106 years ago, and fluvial morphologies are preserved on scales of a few metres. Peak discharges are estimated as more than 107 m3 s-1. Our data indicate that the water originated in the region north of the Cerberus Plains, and was probably related to volcanic processes.Key words Mars; Marte Vallis; Cerberus Plains; longitudinal grooving; streamlined forms


Jökulhlaup deposits at the Ásbyrgi Canyon, northern Iceland: sedimentology and implications for flow type

ÓSKAR KNUDSENKlettur Consulting Engineers, Bíldshöfða 12, IS-102 Reykjavík, Icelande-mail: [email protected]

ANDREW J. RUSSELL

School of Earth Sciences and Geography, Keele University, Keele, Staffordshire ST5 5BG, UKe-mail: [email protected]

Abstract Most research into the impact of Icelandic jökulhlaups has concentrated on large relatively unconfined outwash plains in the south of Iceland. By contrast, here is only a limited picture of the magnitude, rheology, geomorphic impact and sedimentology of floods draining to the north from the Vatnajökull Glacier. This paper presents sedimentary evidence of jökulhlaup deposits at the Ásbyrgi Canyon. The sedimentary succession consists of large-scale sandy trough cross-bedded units capped by a boulder-rich unit. These deposits are interpreted as the product of a hyperconcentrated flow. The location of the pit and the boulder surface suggests these flows emanated from the present river course of the Jökulsá á Fjöllum River. The last period of jökulhlaup activity within the Jökulsá á Fjöllum River was in the early–mid eighteenth century when a series of jökulhlaups inundated the lowlands north of the Ásbyrgi Canyon. The fact that the historical floods within the Jökulsá á Fjöllum River were hyperconcentrated suggests that these floods may have had a subglacial volcanic origin.Key words jökulhlaup deposits; hyperconcentrated flow; Ásbyrgi; northern Iceland; Jökulsá á Fjöllum; geomorphic impact; subglacial volcanism; boulder-rich sediment units


Evidence for province-wide water storage and catastrophic drainage beneath the Laurentide Ice Sheet, Alberta, Canada

MANDY J. MUNRO-STASIUKDepartment of Geography, Kent State University, Kent, Ohio 44242-0001, USAe-mail: [email protected]

DARREN B. SJOGRENEarth Science Program, University of Calgary, Calgary, Alberta T2N 1N4, Canada

Abstract The landscape in Alberta, Canada, is dominated by a single province-wide landscape unconformity. This unconformity is marked by erosional fluted and hummocky terrain, which cuts into all local bedrock and sediment. Sedimentology, geomorphology and topography all indicate erosion by enormous volumes of water that flowed under the Laurentide Ice Sheet at, or soon after, the last glacial maximum. Widespread glaciolacustrine beds that are preserved in preglacial valleys in south-central Alberta, attest to water storage before the giant flood. We propose that most of the natural depressions in the preglacial valley network in Alberta acted as an enormous inter-connected cavity system that was operational prior to the flood that created the landscape unconformity. This cavity system was capable of storing a significant volume of water in the range of hundreds of cubic kilometres.Key words subglacial meltwater; Laurentide Ice Sheet; water storage; catastrophic drainage


Catastrophic floods in Iceland

HAUKUR TÓMASSONNational Energy Authority, Grensásvegur 9, IS-108 Reykjavík, Icelande-mail: [email protected]

Abstract The paper describes four extreme or catastrophic floods in Iceland and the associated processes and landforms. These floods span the time from the last Ice Age up to the present century. Catastrophic floods defined as peak flows larger than 100 000 m3 s-1 normally have occurred twice a century in Iceland for thousands of years. The last event of this kind occurred in 1918 with the eruption of the Katla Volcano underneath the Mýrdalsjökull Glacier. Several km3 of water and ice were then transported in an immense glacier burst, and over 0.9 km3 of magma was brought to the surface. The peak flow was estimated to be of the order of 300 000 m3 s-1. A catastrophic flood occurred in the Jökulsá á Fjöllum River some 2500 years ago during which the huge Jökulsá Canyon was eroded. The total erosion of solid rock equalled some 0.55 km3, and the peak flow was likely of the order of 500 000 m3 s-1. This is the greatest of all known catastrophic floods in Iceland. It most likely originated in the Bárðarbunga caldera in the Vatnajökull Glacier. A catastrophic flood occurred about 9500 years ago in the basin of the Hvítá River in southern Iceland. This flood originated in an ice dammed lake at Kjölur, and its peak flow has been estimated to be of the order of 200 000 m3 s-1.Key words catastrophic; jökulhlaup; peak flow; landforms; caldera; eruption; canyon; ice-dam lake; Iceland


The most severe floods of the Tiber River in Rome

MARIA GABRIELLA ALESSANDRONIVia di Grotta Perfetta 343, I-00142 Rome, Italyfax: +39 06 5941827

GIANRENZO REMEDIAUniversity of l’Aquila, Faculty of Engineering, I-67040 Monteluco di Roio, l’Aquila, Italye-mail: [email protected]

Abstract The paper reviews the floods which caused inundations in Rome during the long period from 414 BC until 31 December 1999. Then an analysis of the rainfalls related to the most severe floods during the twentieth century shows the strong variability of the drainage basin inflows. The study examines the correlation between peak discharges, maximum mean daily discharges, flood volumes and rainfall on the basin, distributed among three different phases: a preparatory phase, an antecedent phase and a contemporary phase. Correct forecasts of future floods must take into account not only the contemporary rainfall, but also the moisture of the soil, caused by the first and/or the second phases of precipitation.Key words extraordinary historical floods; rainfall–runoff; preparatory, antecedent and contemporary precipitation; Rome


Extraordinary summer flood in a karst area: case study in Croatia

BORIS BERAKOVICFaculty of Civil Engineering, University of Zagreb, Kaciceva 26, 10000 Zagreb, Croatiae-mail: [email protected]

KSENIJA CESARECMeteorological and Hydrological Service, Gric 3, 10000 Zagreb, Croatiae-mail: [email protected]

Abstract In July 1999 a sudden flood in the Ogulin area in Croatia surprised even the water management experts. The town of Ogulin is situated in a karstic area. Waters from this area are effluents of the Sava River through a number of sinks. In this paper a review of earlier flooding is given; the work to prevent flooding is described including a hydroelectric power plant which reduces the water flow to the sinks. An analysis of the 1999 extreme flood is given. Also damage caused by the flood and measures to improve protection are described.Key words flood; rainfall; karst; sink; hydropower plant; reservoir; torrent; case study


Recent extreme weather events in the Nepal Himalayas

SURESH RAJ CHALISEMountain Natural Resources Division, International Centre for Integrated Mountain Development (ICIMOD), GPO Box 3226, Kathmandu, Nepale-mail: [email protected]

NARENDRA RAJ KHANALCentral Department of Geography, Tribhuvan University, Kirtipur, Kathmandu, Nepal

Abstract Extreme weather events and disasters induced by them seem to be on the increase in the Himalayas in recent years. If glacier lake outburst floods (GLOF) occur more frequently in the high mountains, then floods and landslide events become more frequent in the middle hills and the lower plains. Such disasters associated with extreme weather events cause widespread damage to life and property and destroy valuable infrastructure in the mountains and the adjoining plains every year, severely affecting the pace of development in Nepal. Although, precipitation is the principal triggering factor for such disasters, the fragile and active geology of the Himalaya Mountains, extremely steep slopes and the recent indiscriminate changes in land use and land cover further exacerbate the problem.Key words extreme weather events; natural disasters; glacial lake outburst floods; landslide damming; floods; Nepal; physiography; Himalayas


The flood of the floods—Poland, summer 1997

ZBIGNIEW W. KUNDZEWICZResearch Centre for Agricultural and Forest Environment, Polish Academy of Sciences, Bukowska 19, 60-809 Poznań, Polande-mail: [email protected]

Abstract The flood hitting the drainage basins of the Odra River and the Vistula River in summer 1997 has been labelled the largest natural disaster in the 1000-year history of Poland. It caused 54 fatalities and material losses of the order of billions of US dollars; in this latter category it was an

all-time high. From the hydrological point of view, this flood was a very rare event, with a return period in some river cross-sections of the order of several hundred years or more. Since only minor floods had occurred in Poland for several years before 1997 the awareness and preparedness of the nation was weakened. It is clear that the disaster could not have been avoided, yet improvement of the flood-preparedness system would have significantly reduced the losses.Key words river floods; flood protection; flood preparedness; extreme weather events; Odra River, Poland


Historic extreme floods as input to dam safety analyses

GRETHE HOLM MIDTTØMMEDepartment of Hydraulic and Environmental Engineering, The Norwegian University of Science and Technology, S. P. Andersens Vei 5, N-7491 Trondheim, Norwaye-mail: [email protected]

JENS KRISTIAN TINGVOLDGlommen’s and Laagen’s Water Management Association, PO Box 2903 Solli, N-0230 Oslo, Norwaye-mail: [email protected]

Abstract In a case study of the Vinstra River, a tributary of the River Gudbrandsdalslågen in Norway, hydrological data from the extreme floods in 1789 and 1938 have been collected, as well as descriptions of the consequences, in order to create reliable flood scenarios for emergency action planning for dams. HBV models (named after the abbreviation of Hydrologiska Byråns Vattenbalansavdeling/Hydrological Bureau Water Balance Section, at the Swedish Meteorological and Hydrological Institute) for several of the River Gudbrandsdalslågen sub-basins have been adapted to extreme flood simulations and data from the 1938 flood have been used for calibration. The calibrated HBV models have been used in an effort to reconstruct the 1789 flood and some preliminary results are presented.Key words dam safety; flood scenario; historic floods; extreme flood simulation; HBV model; Norway


A study of extreme storm events in the Greater Athens area, Greece

MARIA MIMIKOU, EVANGELOS BALTAS & EKATERINI VARANOUDepartment of Civil Engineering, National Technical University of Athens, 5 Iroon Polytechniou, 15773 Athens, Greecee-mail: [email protected]

Abstract The current paper examines two intense flood-producing rainstorms that occurred in October 1994 and July 1995 and which caused severe damage and loss of life in the Greater Athens Greece area. The October 1994 flood event is one of the most serious observed among the extreme flood events of the last 30–40 years. The return period of the October storm was estimated to be 100 years. The July 1995 flood event was caused be a storm of convective type with a short duration and intensity extremely varying in space. The return period of the July storm was estimated to be 14–15 years.

mailto:[email protected]

mailto:[email protected]

Key words extreme storm events; floods; statistical analysis; Athens


Highest floods in India

P. R. RAKHECHAIndian Institute of Tropical Meteorology, Pune, Indiae-mail: [email protected]

Abstract This paper provides information on the highest recorded floods at some sites in India’s major river basins. The data available for the last 100 years or so indicate that the highest floods recorded on rivers in India had peak discharges ranging from 1170 m3 s-1 for a 133 km2 area to 72 900 m3 s-1 for a 935 000 km2 area. The flood comparison studies showed that the highest recorded floods in India are remarkably comparable with the highest floods reported from other parts of the world for drainage areas larger than 1000 km2. Two powerful floods recorded in India—the flood of 6 September 1970 on the Narmada River and the flood of 11 August 1979 on the Machhu River were found to be record-breaking events in the world.Key words highest floods; summer monsoon; cyclonic storm; heavy rainfall; spillways; Indian rivers; envelope curve


The large flood of 1860 in Norway

LARS ANDREAS ROALDNorwegian Water Resources and Energy Directorate (NVE), Box 5091 Majorstua, N-0301 Oslo, Norwaye-mail: [email protected]

Abstract In 1860 a large and widespread flood occurred over eastern Norway causing extensive damage. The extent and causes of this flood are examined. The period between 1846 and 1870 had an over-abundance of large floods, which is typical for cold periods with a significant contribution from extensive snowmelt. Flood warnings were issued before the 1860 flood and several measures were taken to reduce the flood damage.Key words flood hydrology; case study; flood causes; damage mitigation; Norway


A stochastic model for exploring extreme flood events in the UK

HARVEY J. E. RODDA, AGNETE BERGER & ROBERT MUIR-WOODRisk Management Solutions Ltd, 10 Eastcheap, London EC3M 1AJ, UK

Abstract This paper describes the development of a new stochastic model capable of predicting the depth and return periods of extreme flood events for both individual and combinations of basins within the UK. The model is based on analysing the meteorological controls of floods

from a database of approximately 500 extreme historical events. By utilizing the variations in the controlling meteorological parameters (such as total rainfall, duration of rainfall, and the rate of storm movement), a stochastic set of characteristic extreme rainfall footprints was derived. By combining this with antecedent conditions, it is possible to explore the potential for flood events with return periods greater than 1000 years. The results will be used to estimate the degree and location of damage and financial losses following an extreme flood event.Key words flood modelling; rainfall modelling; extreme rainfall events; insurance; flood risk mapping


Relative roles of geomorphology and water input distribution in an extreme flood structure

CHRISTOPHE CUDENNEC, FREDERIC GOGIENDépartement Génie Rural, Ecole Nationale Supérieure Agronomique, F-35042 Rennes Cedex, Francee-mail: [email protected]

JACQUES BOURGESInstitut de Recherche pour le Développement, Mission en Tunisie, BP 434, 1004 El Menzah, Tunisia

JEAN DUCHESNEDépartement Paysage, Institut National Horticole, F-49045 Angers Cedex 01, France

RIDHA KALLELDirection Eaux de Surface, Direction Générale des Ressources en Eau, 43 Rue de la Manoubia, 1008 Tunis, Tunisia

Abstract An extreme flood is often caused by a highly variable rainfall event on a basin. We propose a method for taking this variability into account in a geomorphological unit hydrograph computation. We apply this method to a basin in central Tunisia and show how the combination of geomorphology and water input distribution effects the flood composition.Key words rainfall–runoff modelling; geomorphological unit hydrograph; rainfall variability; semiarid


Surge-related floods at Skeiðarárjökull Glacier, Iceland: implications for ice-marginal outwash deposits

THAIËNNE A. G. P. VAN DIJKSchool of Earth Sciences and Geography, Keele University, Keele, Staffordshire ST5 5BG, UKe-mail: [email protected]

ODDUR SIGURÐSSONVatnamælingar (Hydrological Service), Orkustofnun (National Energy Authority), Grensásvegi 9, 108 Reykjavík, Iceland

Abstract Floods induced by the 1991 surge of the Skeiðarárjökull Glacier deposited three ice-marginal fans at new tunnel outlets. Photographic evidence indicates the timing of tunnel use and

fan deposition, and provides qualitative flow data. Sedimentary characteristics reveal gradual fan aggradation by deposition from continuous turbulent water flow, and an overall increase in discharge and discharge fluctuation during the surge.Key words surge-type glaciers; glacier hydrology; surge-induced floods; glaciofluvial; proglacial outwash fans; Skeiðarárjökull, Iceland


Real-time monitoring of glacial rivers in Iceland

SVERRIR ÓSKAR ELEFSEN, ÁRNI SNORRASONNational Energy Authority, Hydrological Service, Grensásvegur 9, IS-108 Reykjavík, Icelande-mail: [email protected]; [email protected]

HREINN HARALDSSONPublic Roads Authority, Borgartún 5, IS-105 Reykjavík, Iceland

SIGURÐUR REYNIR GÍSLASONUniversity of Iceland, Science Institute, Dunhagi 3, IS-107 Reykjavík, Iceland

HREFNA KRISTMANNSDÓTTIRNational Energy Authority, Geoscience Division, Grensásvegur 9, IS-108 Reykjavík, Iceland

Abstract The Hydrological Service in Iceland initiated a real-time monitoring system of rivers in 1998 as a response to the catastrophic flood in the River Skeiðará in 1996. Prior to this, suitable equipment was chosen and the background chemical composition of selected glacial rivers was studied. The system includes 26 stations with real-time connection of which 10 can be classified as geochemical warning stations for floods caused by subglacial geothermal activity or eruptions. The geochemical warning stations are located on glacial rivers draining the Mýrdalsjökull Glacier and the Vatnajökull Glacier. The system is accessible on the Internet, but it is also designed to give automatic warnings. During the first two years of operation, moderate floods as well as small-scale geochemical leakages have both been detected by the system.Key words real-time monitoring; geothermal activity; subglacial eruption; dissolution; electrical conductivity


Formation of kettle holes following a glacial outburst flood (jökulhlaup), Skeiðarársandur, southern Iceland

HELEN FAYSchool of Earth Sciences and Geography, Keele University, Keele, Staffordshire ST5 5BG, UKe-mail: [email protected]

Abstract The 1996 jökulhlaup on Skeiðarársandur, southern Iceland, involved the transport of ice blocks released from the glacier margin. The morphology, sedimentology and spatial distribution of kettle holes and other ice-block-related features, which developed post-flood in this proglacial fluvial system, were examined. Four types of phenomena are described and explained: kettle chains orientated both parallel and transverse to the principal palaeoflow direction, hummocky

topography, steep-walled and inverse-conical kettle holes, and conical sediment mounds.Key words kettlehole; jökulhlaup; ice block; Iceland; glacier; sandur; morphology; sedimentology


Characterizing the flash flood hazards potential along the Red Sea coast of Egypt

EMAN M. GHONEIM, NIGEL W. ARNELL & GILES M. FOODYDepartment of Geography, University of Southampton, Highfield, Southampton SO17 1BJ, UKe-mail: [email protected]

Abstract This paper describes an attempt to characterize the flash flood potential in the wadi El-Alam, on the Red Sea coast of Egypt. Many important basin characteristics and morphometric parameters were defined from a digital elevation model (DEM). The range of hydrograph characteristics was estimated and the flood-vulnerable sites along the Idfu-Marsa Alam road identified.Key words geographical information system (GIS); digital elevation model (DEM); morphometric parameters; flash floods; dry wadis; Red Sea coast; eastern Egyptian desert; road network; risk categories


Erosion and deposition in the proglacial zone: the 1996 jökulhlaup on Skeiðarársandur, southeast Iceland

BASIL GOMEZGeomorphology Laboratory, Indiana State University, Terre Haute, Indiana 47809, USAe-mail: [email protected]

ANDREW J. RUSSELLSchool of Earth Sciences and Geography, Keele University, Keele, Staffordshire ST5 5BG, UK

LAURENCE C. SMITHDepartment of Geography, University of California, Los Angeles, California 90095, USA

ÓSKAR KNUDSENKlettur Consulting Engineers, Bíldshöfða 12, Reykjavík IS-112, Iceland

Abstract The November 1996 jökulhlaup from Skeiðarárjökull Glacier, Iceland, had little impact on the proximal surface of Skeiðarársandur, though most channel change occurred in the proximal zone. Patterns of erosion and deposition were revealed by aerial photography, repeat-pass interferometry and field survey. The jökulhlaup bypassed the proximal zone because meltwater ponded in an ice-marginal depression, which regulated the flow of water and calibre of sediment supplied to Skeiðarársandur, and most drainage was through a single primary outlet (the Gígjukvísl River). The geomorphic impact of jökulhlaups may vary between periods of glacier advance when a glacier and sandur are coupled and active aggradation occurs in the proximal zone, and periods of glacier retreat when the glacier is decoupled from the sandur. The style of

sedimentation in rivers which route water and sediment directly on to the sandar will also differ from that in rivers buffered by ponding in the proglacial zone.Key words sandur; Iceland; interferometry; jökulhlaup; proglacial zone


Seasonal variation in the chemistry of glacial-fed rivers in Iceland

HREFNA KRISTMANNSDÓTTIROrkustofnun, Grensásvegur 9, IS-108 Reykjavík, Icelande-mail: [email protected]

SIGURÐUR R. GÍSLASONScience Institute, University of Iceland, Dunhagi 3, IS-107 Reykjavík, Iceland

ÁRNI SNORRASONOrkustofnun, Grensásvegur 9, IS-108 Reykjavík, Iceland

HREINN HARALDSSON Public Roads Authority, Borgartún 5, IS-105 Reykjavík, Iceland

STEINUNN HAUKSDÓTTIR & ÁSGEIR GUNNARSSONOrkustofnun, Grensásvegur 9, IS-108 Reykjavík, Iceland

Abstract Ten Icelandic rivers have been monitored at 11 sites throughout one year to obtain baseline values for the design of warning systems based on chemical changes preceding subglacial volcanic eruptions. Seasonal changes characteristic of each river have been identified as well as alarm values for chosen parameters. Six pilot systems based on the measurement of conductivity have been put into operation and run for several months. The conductivity of water at the sites varies from 20 to more than 300 S cm-1 between rivers and seasons. During jökulhlaups, conductivity may exceed 700 S cm-1. Other potential parameters to monitor for warning purposes are hydrogen sulphide and mercury. Tests have been run collecting data on those substances for continuous measurement, but practical methods to operate such stations have not yet been developed.Key words seasonal variation; glacial rivers; monitoring; volcanic; geothermal; jökulhlaup; subglacial eruption; conductivity; mercury; hydrogen sulphide


Geochemical warning for subglacial eruptions—background and history

HREFNA KRISTMANNSDÓTTIR, ÁRNI SNORRASONOrkustofnun, Grensásvegur 9, IS-108 Reykjavík, Iceland e-mail: [email protected]; [email protected]

SIGURÐUR R. GÍSLASON

Science Institute, University of Iceland, Dunhagi 3, IS-107 Reykjavík, Iceland

HREINN HARALDSSONPublic Roads Authority, Borgartún 5, IS-105 Reykjavík, Iceland

ÁSGEIR GUNNARSSON, STEINUNN HAUKSDÓTTIR & SVERRIR Ó. ELEFSENOrkustofnun, Grensásvegur 9, IS-108 Reykjavík, Iceland

Abstract Early detection of the runoff from a volcanic event may save lives, property and infrastructure such as road constructions, power plants and power distribution systems. The project described herein aims at designing automatic warning systems based on monitoring chemical changes of glacial rivers draining the Vatnajökull Glacier and the Mýrdalsjökull Glacier in Iceland. First, background data have to be collected and seasonal variations determined, as well as suitable parameters to monitor and their alarm levels. Secondly appropriate detectors are chosen and designed for the different locations of concern and pilot systems operated experimentally.Key words geochemical warning; subglacial eruption; glacial rivers; conductivity; jökulhlaup; monitoring; detectors; alarm value; volcanic; geothermal


Criteria for distinguishing high magnitude flood events in the proglacial fluvial sedimentary record

PHILIP M. MARRENSchool of Earth Sciences and Geography, Keele University, Keele, Staffordshire ST5 5BG, UK

Abstract Recognizing high magnitude or extreme floods in the sedimentary record is important if estimates of their geomorphic and sedimentary significance over long time scales (i.e. 102–103

years) are to be made. Standard regime or palaeocompetence based palaeohydraulic approaches present one set of solutions to this problem. An alternative is to examine the sedimentary record to determine the dominant depositional processes in any particular environment. Specifically, it is important to assess the role of high magnitude floods within the sedimentary record. This paper presents a set of criteria, based on flow rheology, sediment structures, clast orientation and sediment architecture and geometry, which are designed to critically determine the magnitude–frequency regime of fluvial sediments. The criteria were derived from literature on the sedimentary impact of high magnitude floods and from fieldwork in southeast Iceland.Key words catastrophic flooding; magnitude and frequency; jokulhlaup; glaciofluvial; sandur; braided rivers; sedimentology; palaeohydrology


The influence of channel flood history on the impact of the November 1996 jökulhlaup, Skeiðarársandur, Iceland

ANDREW J. RUSSELLSchool of Earth Sciences and Geography, Keele University, Keele, Staffordshire ST5 5BG, UK



Abstract Multiple channel occupation during the November 1996 jökulhlaup Skeiðarársandur, Iceland, provided an opportunity to assess the role of flood history in controlling the varied impact of a single large jökulhlaup. This paper considers the immediate geomorphological impact of the 1996 jökulhlaup in relation to the flood history of each major ice-proximal channel system draining Skeiðarárjökull Glacier. The jökulhlaup had greatest impact on the Gígjukvísl River channel, whilst the Skeiðará River and Sæluhúsavatn River channels were impacted to a lesser degree. The jökulhlaup had very little impact on the Háöldukvísl River and the Súla River. Large jökulhlaup impact within the central portion of the glacier occurred because non-jökulhlaup flows had dominated the central portion of the glacier for many years. The impact of the 1996 jökulhlaup on individual channels is strongly influenced by each channel’s flood history, which in turn is driven by differential rates of glacier margin retreat.Key words November 1996 jökulhlaup; Skeiðarársandar; Iceland; flood history; geomorphological outwash plain; glacier margin retreat; impact


Impact of the July 1999 jökulhlaup on the proximal River Jökulsá á Sólheimasandi, Mýrdalsjökull Glacier, southern Iceland

ANDREW J. RUSSELLSchool of Earth Sciences and Geography, Keele University, Keele, Staffordshire ST5 5BG, UKe-mail: [email protected]

FIONA S. TWEEDDepartment of Geography, Staffordshire University, College Road, Stoke-on-Trent, Staffordshire ST4 2DE, UKe-mail: [email protected]


MATTHEW J. ROBERTS, TIMOTHY D. HARRISDepartment of Geography, Staffordshire University, College Road, Stoke-on-Trent, Staffordshire ST4 2DE, UKe-mail: [email protected]

PHILIP M. MARRENSchool of Earth Sciences and Geography, Keele University, Keele, Staffordshire ST5 5BG, UKe-mail: [email protected]

Abstract Few studies have focused on the geomorphic and sedimentary impact of magmatically-generated jökulhlaups released directly into the proglacial zone. This paper characterizes the proglacial geomorphic and sedimentary impact of the 17–18 July 1999 jökulhlaup, Glacier Sólheimajökull, Iceland. Jökulhlaup outflow from the glacier margin resulted in temporary water storage within former ice-dammed lake basins, resulting in the deposition of coarse-grained deltas, and more distal sandy bedforms capped by silts. Outflow from the western outlet transported boulders up to 8 m in diameter on the surface of a new outwash fan ranging in

thickness from 6 m proximally to 1 m distally. Near-simultaneous deposition of ice blocks, boulders and finer-grained matrix occurred, suggesting that flows were sediment rich during the rising stage of the flood. This unexpected short-lived flood had a distinctive impact on the proglacial zone, providing a record of a precursor to a Mount Katla eruption.Key words Jökulsá á Sólheimasandi; Mýrdalsjökull; Iceland; geomorphological impact; ice blocks; temporary storage; outwash fan; proglacial; Katla; boulders


Dam design flood estimation based on bivariate extreme-value distributions

ÁLVARO A. ALDAMA & ALDO I. RAMÍREZInstituto Mexicano de Tecnología del Agua, Paseo Cuauhnáhuac 8532, Col. Progreso, Jiutepec, Morelos, CP 62550, Mexicoe-mail: [email protected] or [email protected]

Abstract Design floods for dams and reservoirs are often estimated using flood frequency analysis of maximum annual discharges. A design flood is fully characterized by a hydrograph, which is routed through the reservoir in order to determine its flood control capacity and the spillway design discharge. Due to flood frequency analyses relying upon the estimation of probability distributions associated with peak discharges only, the design hydrograph is fully determined by using arbitrary procedures. The description of a hydrograph must at least involve its most important parameters, namely: peak discharge and runoff volume. On the basis of this result, a new approach for estimating the design flood of dams and reservoirs has been developed. The method is based on the use of the bivariate extreme-value probability distribution of peak discharge and volume. An application example is also presented.Key words design flood; hydrograph parameterization; bivariate extreme value distribution; joint return period; Logistic model; mixed marginal Gumbel distribution


Study of parameter estimation methods for Pearson-III distribution in flood frequency analysis

CHEN YUANFANG, HOU YUDepartment of Hydrology, Hohai University, Nanjing 210024, Chinae-mail: [email protected]

PIETER VAN GELDERFaculty of Civil Engineering and Geosciences, Delft University of Technology, Delft 2600 GA, The Netherlandse-mail: [email protected]

SHA ZHIGUIYangtze Water Resources Commission, Wuhan 430010, China

Abstract Based on the Monte-Carlo method, the main parameter estimation methods for the Pearson-III (P-III) distribution are comprehensively compared, including traditional moments

(MOM), curve-fitting, probability weighted moments (PWM) and weighted function moments (WF) which has been developed recently in China. In the comparison, series with historical floods are generated not only in the Chinese given-number model, but also in the Stedinger–Hirsch model (threshold model). Two criteria for evaluation of an estimation method are considered. One criterion is the bias and efficiency of the parameters and design flood values (quantiles) with a fixed probability, the other is the bias and efficiency of the probability of failure of a design flood. Many calculations show that the PWM and a curve-fitting method with absolute norm are the two best estimation methods of the P-III distribution in flood frequency analysis.Key words Pearson-III; flood frequency analysis; Monte-Carlo; probability weighted moments; historical flood; bias and efficiency; flood sampling models; curve-fitting; comparison; quantile; probability of failure


Assessment of a simplified runoff model for theoretical derivation of the probability distribution of floods

GIUSEPPE GIOIA, VITO IACOBELLISDipartimento di Ingegneria delle Acque, Politecnico di Bari, Via E. Orabona 4, I-70125 Bari, Italye-mail: [email protected]

MARIA ROSARIA MARGIOTTADipartimento di Ingegneria e Fisica dell’Ambiente, Università della Basilicata, Contrada Macchia Romana, I-85100 Potenza, Italye-mail: [email protected]

Abstract In recent years probability distributions of annual maximum flood peaks have been extensively studied by means of standard statistical methods, not always accounting for the physical meaning of the used variables and parameters. We discuss a simplified rainfall–runoff model proposed for theoretical derivation of probability distributions of rainfall generated extreme floods, mainly controlling the flood process in the Mediterranean area. The assessment of such a simplification can be performed by means of a numerical investigation, which tries to represent as much as possible the natural variability of rainfall and basin response. In this paper first results are presented, mainly focusing on different characteristics of hydrological losses with their climatic signatures and classification.Key words flood frequency; climate; rainfall–runoff; variable contributing area; Monte Carlo simulation; Mediterranean basins; south Italy________________________________________________________________________The Extremes of the Extremes: Extraordinary Floods (Proceedings of a symposium held at Reykjavik, Iceland, July 2000). IAHS Publ. no. 271, 2002. pp. 277–282.

Power law distribution of catastrophic floods

CARLO DE MICHELEDIIAR, Politecnico di Milano, I-20132, Piazza Leonardo da Vinci 32, I-20133 Milan, Italye-mail: [email protected]

PAOLO LA BARBERAUniversity of Genoa, Via Montallegro 1, I-16145 Genoa, Italy

RENZO ROSSODIIAR, Politecnico di Milano, I-20132, Piazza Leonardo da Vinci 32, I-20133 Milan, Italy

Abstract This paper is based on the conjecture that catastrophic events follow a simple pattern as inferred by Feder (1988), Turcotte (1992) and Bak (1997) which were derived from observations of different geophysical, geological and biological phenomena. The spatial distribution of catastrophic floods, i.e. floods that cause damage and loss of life, is investigated here by combining the scaling properties of extreme floods with those of river network composition. Accordingly the spatial pattern of catastrophic floods is described by a power law in the form Pr[Q > q] -/m which indicates that the probability of occurrence of a flood exceeding a value of q is a power law function of basin area. The exponent /m is determined from the parameters characterizing river flows, m, and river network composition, . An application using major floods in Thyrrhenian Liguria, northwestern Italy, during one century successfully tests this conjecture.Key words catastrophic floods; power law; scaling


The probable maximum flood at the Ukai and Lakhwar dam sites in India

P. R. RAKHECHA* & C. CLARKCHRS, Shute Lane, Bruton, Somerset, UKe-mail: [email protected]

Abstract The design of impounding structures where failure would lead to catastrophic loss of life requires an estimate of the probable maximum flood. In India there are over 3000 dams and more are being built and planned to meet the needs for water supply, power, and irrigation. Recently, revised estimates of probable maximum precipitation have been published. These new estimates are used in conjunction with instantaneous unit hydrographs (IUH) to assess the safety of two dam sites: the Lakhwar dam on the Yamuna River, and the Ukai dam on the Tapi River. The results show that at the first site the outflow exceeded the design value of the spillway by a factor of 2.27, while at the second site the ratio was 2.25. The IUH results are supported by flood frequency analyses using a modified Gumbel scale and also results derived from the Rational method. These outcomes illustrate that in India more attention to dam safety is a dire need for the future.Key words dam safety; probable maximum precipitation; flood frequency________________________________________________________________________The Extremes of the Extremes: Extraordinary Floods (Proceedings of a symposium held at Reykjavik, Iceland, July 2000). IAHS Publ. no. 271, 2002. pp. 289–297.

Estimation of extreme Pareto quantiles using upper order statistics

ÓLI G. B. SVEINSSONDepartment of Civil Engineering, Colorado State University, Fort Collins, Colorado 80523, USAe-mail: [email protected]

DUANE C. BOESDepartment of Statistics, Colorado State University, Fort Collins, Colorado 80523, USA

JOSE D. SALASDepartment of Civil Engineering, Colorado State University, Fort Collins, Colorado 80523, USA

Abstract A common feature of certain hydrological data plotted vs their return period on a log-log scale is an apparent straight line fit at the upper end. This is compatible with an assumed two-parameter Pareto model for the upper end. The objective of this study is to utilize only the largest sample observations in the estimation of extreme upper quantiles. Parameters of the Pareto are estimated based on the upper order statistics at a single site using maximum likelihood. Also, regional estimates are obtained under an assumed indexing method that yields a type of regional homogeneity. Exact formulas for the mean squared error of quantile estimators are given. Extreme precipitation data from the northern front range of Colorado, USA, are used for illustrating the procedures.Key words extreme events; floods; frequency analysis; index flood; order statistics; power law


A study on threshold selection in POT analysis of extreme floods

SHIGENOBU TANAKAToyohashi Works Office, Chubu Regional Development Bureau, Ministry of Land, Infrastructure and Transport, 1–6 Hiranishi, Nakano-cho, Toyohashi, Aichi 441-8149, Japane-mail: [email protected]

KAORU TAKARADisaster Prevention Research Institute, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japane-mail: [email protected]

Abstract The annual maximum series (AMS) and the peaks-over-threshold series (POT) of extreme values of floods and storms have been used for frequency analysis. It has been shown that the POT procedure is better than the AMS one in the case of short records. There remains, however, the crucial decision of how to choose a threshold value in POT analysis. This paper discusses methods of choosing the threshold in POT analysis. The exponential distribution and the generalized Pareto distribution are used for samples of mean areal rainfalls, which have no clear predetermined physical threshold. In order to select the optimal threshold (the optimal number of upper extremes), the authors have compared the fluctuations of six indices due to the change of the number of upper extremes included in the analysis. This comparison has revealed that parameters of distribution always perform excellently to identify the optimal number of upper extremes and that some of the indices can be used to reject a range with an undesirable threshold.Key words peaks over threshold; partial duration series; annual maximum series; generalized extreme-value distribution; generalized Pareto distribution; L-moment; shape parameter; mean excess function; 3-h rainfall; 100-year quantile


Water level forecasts for Lake Managua

KARI AHTIFinnish Meteorological Institute, PO Box 503, FIN-00101 Helsinki, Finland


LUIS SANDOR PALACIOS RUIZ Instituto Nigaraguense Estudios Territoriales, AP 2110 Frente a Policlinica Oriental del INSS, Managua, Nicaraguae-mail: [email protected]

Abstract In October 1998, (Hurricane Mitch) the water level of Lake Managua (Nicaragua) rose about 4 m. The water level is still so high that there is evident risk of a serious flash flood. There was a need for forecasts of the water level. There were no telemetric hydrological data available. So the only possibility was to use precipitation data from meteorological stations and water level observations. Three different forecasts were developed: a monthly forecast for the rainy season, a monthly forecast for the dry season and a flash flood forecast. It was found that three daily reporting meteorological stations were enough for the flash flood forecast. The flash flood model has been tested using observations during Hurricane Mitch. Correlation coefficients of the water level forecasts in the model and observed water levels were r = 0.99 for the 1-day forecast and r = 0.98 for the 2-day forecast.Key words flood; forecast; precipitation; ENSO; climate; hurricane; bifurcation; Nicaragua; correlation; water level


Flood inundation maps—mapping of flood prone areas in Norway

HALLVARD BERGNorwegian Water Resources and Energy Directorate (NVE), PO Box 5091 Majorstua, N-0301 Oslo, Norwaye-mail: [email protected]

Abstract The Norwegian flood inundation map project was initiated by the Norwegian Water Resources and Energy Directorate (NVE) after a major flood in 1995 and aims at reducing flood damage through improved land-use planning and emergency preparedness. The project includes 188 river stretches, covering 1750 km of river length. The determination of inundated area is calculated by using geographic information systems. A digital elevation model (DEM) with a high horizontal resolution and a high vertical accuracy is produced. The flood surface elevation model is based on the computed water levels in cross-sections from the hydraulic model. The flood surface elevations are subtracted from the DEM, which results in negative values at inundated areas. The modelling is performed for six different flood levels, the 10-, 20-, 50-, 100, 200- and 500-year floods, and flood inundation maps are produced for each flood level.Key words flood inundation mapping; flood estimation; hydraulic modelling; GIS; acceptable risk; Norway


Application of the stochastic self-training procedure for the modelling of extreme floods

VADIM KUZMINDepartment of Hydrology, Russian State Hydrometeorological University, Malookhtinski 98, St Petersburg 195196, Russiae-mail: [email protected]

PIETER VAN GELDERDelft University of Technology, Faculty of Civil Engineering, Room 3.87, PO Box 5048, 2600 GA Delft, The Netherlandse-mail: [email protected]

HAFZULLAH AKSOYIstanbul Technical University, Civil Engineering Faculty, Hydraulics Division, 80626 Ayazaga, Istanbul, Turkeye-mail: [email protected]

ISMAIL KUCUKElectrical Power Resources, Survey and Development Administration, Eskisehir Yolu 7. Km, 06520 Ankara, Turkeye-mail: [email protected]

Abstract Modelling techniques valid for ordinary hydrological conditions are often inadequate for catastrophic runoff conditions, as the majority of the parameters included in the modelling schemes are not necessarily applicable to flood conditions. To overcome this problem, using a stochastic self-training procedure (SSTP) is proposed. The procedure is based on the real water balance equation and the statistical model of the water balance. An application of the procedure with data from the Filyos River (Turkey) is presented in this study.Key words extreme floods; river flow forecasting; stochastic models; stochastic self-training procedure; Filyos River basin, Turkey; kinematic wave forecasting


The region of influence approach in complex and highly variable environments—experience from Switzerland

MARTIN PFAUNDLER & PAOLO BURLANDOInstitute of Hydromechanics and Water Resources Management, Federal Institute of Technology Zurich, CH-8093 Zurich, Switzerlande-mails: [email protected]; [email protected]

Abstract The principle of the region of influence (ROI) approach as a flexible method for flood regionalization in geographically complex environments is presented. The various options that are related to this method are outlined and their implications for their actual application for estimating flood quantiles for ungauged basins are discussed and illustrated with a case study. Additionally, the use of further tests applied on the identified regions in order to evaluate their homogeneity is suggested. On the one hand, the many options of the method and its partly subjective character are examined with the aid of the case study. On the other, the advantages offered by the flexibility of the method for use in regions with high spatial variability of the driving flood generation factors are pointed out.Key words flood estimation; ungauged basins; regionalization; index flood; region of influence; Switzerland


Extreme climatic and hydrological events associated with El Niño/Southern Oscillation: analysis (1500–1999) and forecast (2000–

2050)

JORGE SÁNCHEZ-SESMACoordinación de Hidrología, Instituto Mexicano de Tecnología del Agua, Paseo Cuauhnahuac 8532, Jiutepec, Morelos, CP 62550, Méxicoe–mail: [email protected]

Abstract The El Niño/Southern Oscillation (ENSO) is considered one of the most important climatic and hydrological phenomena in the world. Taking into account the possible existence of secular periodic oscillation for ENSO values, a model with periodic component functions has been used to forecast ENSO for the next 50 years, using data from several hundreds of years. The model proposed is based on spectral analysis and linear regression. The results, that are congruent with others obtained by different experimental climate forecasting methods, suggest that the period of maximum ENSO intensity and duration, where we find ourselves right now, could continue for a decade more.Key words extreme floods; climate forecasting; ENSO; century; decade; scale; spectral; analogue


Weighted least squares method—improved estimates when the index flood method is used with annual maximum floods

SAVITHRI SENARATNE & CONLETH CUNNANEDepartment of Engineering Hydrology, National University of Ireland, Galway, Irelande-mail: [email protected]

Abstract The index flood method is one approach in flood frequency analysis to obtain flood estimates at a specific site, in which, the at-site index flood is used along with a regional growth curve. The index flood, in this case the mean annual flood, , is obtained from observed records of streamflow at a nearby gauging station. However, many instances arise where such data are not available. In such ungauged drainage basins, a regression relationship between the mean annual flood and numerically measured drainage basin characteristics such as area, slope, rainfall, etc. is found. A major area of concern in regression relationships has been the presence of heteroscedasticity. This study shows clearly that in such circumstances, based on results from three observed data sets, the use of the weighted least squares method (WLS) with diagonal matrices having their terms equal to inverse coefficient of variation Cv, is superior to the use of the ordinary least squares method (OLS).Key words flood frequency; annual maximum flood; regression; weighted least squares; ordinary least squares; index flood


Simulation of discharge fields

THOMAS SKAUGENNorwegian Water Resources and Energy Directorate (NVE), PO Box 5091 Majorstua, N-0301 Oslo, Norway; and Department of Geophysics, PO Box 1022 Blindern, N-0315 Oslo, Norwaye-mail: [email protected]

Abstract Operative flood forecasting in Norway is based upon the runoff forecast using the Swedish rainfall–runoff model HBV. These results, however, can only be considered as point estimates and it is difficult to extrapolate the results to areas where no such model is calibrated. In this project we aim to quantify the spatial variability of discharge in order to produce simulated scenarios over a certain area and thus be able to issue flood forecasts for areas smaller than the HBV drainage basin. The HBV output is made specific and considered as an estimate of the mean specific discharge for that area. This value acts as a constraint in the simulation of discharge scenarios. Prior to the simulation, specific discharge values from several points within a drainage basin have been analysed with respect to the spatial coverage of discharge intensities. For each day the coverage has been mapped and the overall behaviour can be modelled as a stochastic process. This exercise has been performed for two drainage basins of different physiography and climatic regime with very good results.Key words discharge; simulation; forecasts; spatial variability; scaling; extreme values; HBV


Flood forecasting for the River Rhine in The Netherlands

ERIC SPROKKEREEFInstitute for Inland Water Management and Waste Water Treatment (RIZA), PO Box 9072, 6800 ED Arnhem, The Netherlandse-mail: [email protected]

Abstract The hydrological years 1994 and 1995 were characterized by two extraordinary extreme floods in the basins of the River Meuse and the River Rhine. Water levels were measured with return periods of more than 100 years, considerable damage occurred and as a precaution over 200 000 people had to be evacuated. Both events showed the importance of reliable forecasts with a sufficient forecast period. Until then forecasts for the Rhine River were carried out with a statistical model, allowing a reliable two-day forecast for the Lobith gauging station on the German/Dutch border. To extend this forecast period, a new flood forecasting model was developed. The first operational use of the new model during some minor floods at the beginning of 1999 showed reliable results for the three-day forecast and considerable improvement for the four-day forecast.Key words flood forecasting; River Rhine; flood forecast model; rainfall–runoff; hydraulics


The world’s maximum observed floods

REG HERSCHY2 Queensborough Drive, Reading RG4 7JA, UKe-mail: [email protected]

Abstract Knowledge of exceptionally large floods is essential in solving many problems in water resources management and to assess the susceptibility to flooding of structures in or in the vicinity of rivers. The study, initiated by IAHS, UNESCO and WMO, addresses the collection and analyses of flood data from questionnaires sent to 166 countries. For each country, details are requested for the maximum flood, method of measurement, rainfall if available, hydrological

information and a selection of long-term series of annual maximum floods. Envelope curves of maximum floods are presented. The objective is to update the World Catalogue of Maximum Observed Floods (Rodier & Roche, 1984).Key words maximum floods; catalogues; rainfall–runoff; jökulhlaup; landslide floods; coastal floods


Flood protection in the context of sustainable development

ZBIGNIEW W. KUNDZEWICZResearch Centre of Agricultural and Forest Environment, Polish Academy of Sciences, Bukowska 19, 60-809 Poznan, Polande-mail: [email protected]

Abstract There has been much recent emphasis on sustainable development of water resources, so that the requirements of the present generation are fulfilled without compromizing the ability of future generations to meet their own needs. Destructive floods undermine sustainable development. Systems of flood protection and management are being criticized in the context of sustainable development because they close options for future generations and introduce unacceptable disturbances in ecosystems. A change of paradigm is needed. As a flood protection system guaranteeing complete safety is an illusion, the attitude “living with floods” seems more sustainable than a hopeless striving to “combat floods”.Key words flood protection; sustainable development; sustainability criteria and indices; adaptation


What is an extreme flood and for whom?

DAN LUNDQUISTGlommen’s and Laagen’s Water Management Association, PO Box 2903 Solli, N-0230 Oslo, Norwaye-mail: [email protected]

Abstract Frequently the media report on extreme floods from all over the world. Many of these cause large economic damage to society and even loss of lives, while it is very seldom that they do not pose severe threats to economic assets. Some cover large areas with the gradual inundation of the land being the main issue; others influence only small areas, where intensities can be extremely high and erosion may be a major problem. The meaning of extreme is related to probability, damage potential and scale. These issues are discussed in the context of Norwegian floods during the last 200 years.Key words floods; extremes; probability; flood intensity; economic damage; human influence; flood plains; design floods; hydropower regulation


Extremeness of extreme floods

FERENC PAPPVÍZ-INTER Consulting Engineers, Eszék u. 9–11, H-1114 Budapest, Hungarye-mail: [email protected]

Abstract Any treatise on the extremeness of floods should begin by defining the criteria in terms of which particular floods can be classified as being extreme. These criteria are very likely to differ in the UK, Brazil, Iceland and Hungary. Drawing on the conclusions of former studies and on the data collected from different countries, a proposal is submitted for analysing rare natural flood events. This consists of using the hydrological characteristics of flood waves and the socio-economic losses caused thereby to compile parameters that are easy to handle, are insensitive to the inaccuracies inherent in the basic data and are suited to quantifying the extremeness of a flood event. The three parameters proposed can be used separately or in combination, and they allow previous floods to be classified into nine extremeness categories. Some practical applications of this theoretical approach are presented.Key words drainage basin; extremeness; flood hydrology; peak flood discharge; probability of flood; risk of flooding


Coping with extreme floods: warnings, impacts and response

EDMUND PENNING-ROWSELL & SUE TAPSELLMiddlesex University Flood Hazard Research Centre, Queensway, Enfield, Middlesex EN3 4SF, UKe-mails: [email protected]; [email protected]

Abstract Coping with extreme floods involves reducing the damage that they cause and minimizing their other impacts. This in turn means that we need to understand, first, the impacts of flood warnings on flood damage and on the people and property thereby affected, so that we can manage the total forecasting, warning and response system so as to optimize its impact vis à vis its costs. Secondly, given that we cannot prevent floods and all of their impacts, we need to understand the continuing adverse effects that extreme floods can have on those affected so that we can plan our assistance for these flood victims and minimize the long-term effects.Key words flood warnings; impacts; health effects; social dimensions


Social and economic dimensions of the 1998 extreme floods in coastal Chiapas, Mexico

ALVARO SANCHEZ-CRISPIN & ENRIQUE PROPIN-FREJOMILInstitute of Geography, National University of Mexico, Mexico City 04510, Mexicoe-mail: [email protected]; [email protected]

Abstract Based on empirical research, this paper examines some of the social and economic consequences of the extreme floods that affected the Pacific seaboard of Chiapas, Mexico, during the first few days of September 1998. A tropical region of 10 000 km2 was flooded, which affected

over 800 000 people living in sparsely-populated rural communities and a handful of small and medium-size cities. Due to this natural disaster, over one thousand people were reported dead or missing, land communications were severely damaged and the regional economy was disrupted. One of the major findings of this study is that the extreme flooding was not followed by a massive abandonment of the area; on the contrary, the local population wanted to remain in their original places of residence, participating in actions aimed to reduce the effects of the disaster and waiting for external aid to arrive, particularly governmental assistance.Key words natural disasters; extreme floods; Mexico, coastal Chiapas

International Association of Hydrological Scienceshydrologie.org/redbooks/a271/P271...

Documents

Transcript of International Association of Hydrological Scienceshydrologie.org/redbooks/a271/P271...