Introduction Research Design & Methodology Results

Conclusions

References

Aims & Objectives

GIS Analysis of Coastal Flood Events: A Case Study ApproachProgramme: BSc GeographyName: Cory WilliamsStudent number: 793055Supervisor: Prof. Adrian Luckman

Discussion

· Low lying coastal regions, such as the South and East coast of England are being increasingly exposed to coastal flooding as a result of climate change (Wahl et al., 2011).

· It is crucial that low probability future flooding scenarios are considered due to the huge potential impacts.

· UKCP09 created the H++ scenario which is a high end estimate of the effect of climate change on sea level rise (1.9m) and storm surges (increased height of 0.7m) by 2100.

· Two case studies chosen: The Solent and Humber Estuary.

· Portsmouth and Hull were chosen for more in-depth analysis as following London, these two cities are considered most at risk to coastal flooding in the UK (RIBA & ICE, 2009). Despite this, little literature focuses on them, presenting a research gap.

Figure 1: Case study locations. Humber Estuary (orange) and the Solent (purple).

Research Aim:· To determine the potential impacts of

coastal flooding scenarios for the Solent and Humber Estuary, using Portsmouth and Hull as focussed case studies.

Research Objectives:For each study location and flood scenario:· Calculate the inundated area. · Analyse the impact on property and

estimate associated insurance claims.· Calculate number of people affected.· Calculate the area of different inundated

land cover types.

· Extreme coastal flooding (ECF) is made up of three main constituents: sea level (SL), tides (T) and storm surges (SS) (NTSLF, 2016).

ECF = SL + T + SS· For each region, the main constituents

were combined to create five scenarios with increasing severity.

· SL: contribution begins at mean sea level, increasing with sea level rise up to 1.9m (H++ scenario of UKCP09).

· T: Region specific high astronomical tide values were converted to meters above mean sea level.

· SS: Region specific skew surge values calculated, providing isolated surge water heights.

· GIS analysis carried out at regional scale using ASTER 30m DEM. Using an ‘adapted bathtub’ model, the raster calculator identified cells less than or equal to flood water depth as inundated. The cells not hydrologically connected to coastline were removed.

· Portsmouth and Hull identified as hotspots. In-depth analysis using a high resolution 2m LIDAR DEM was executed. Figure 2 outlines the layers used in this analysis.

Figure 2: Summary of layers used to determine impacts for Portsmouth and Hull.

Figure 3: Five coastal flooding scenarios for Portsmouth.

Figure 4: Land cover classes and postcode centroids for scenario 5 H++ in Portsmouth.

Figure 5: The difference in extent of flooding between water depths of 4.09m and 4.59m in Hull, displaying poor model results.

· Resolution of DEM is a key factor. ASTER DEM vastly underestimated flood extent compared with LIDAR DEM.

· Adapted bathtub model was very simplistic. Ensuring hydrological connectivity produced unrealistic results for Hull. Conversely, it contributed greatly in the Portsmouth analysis.

· Economic analysis of Portsmouth is in accordance with Brown et al. (2011) in a study of the EU as similar increases in flood water depth produce comparable increases in flood damages (multiplication factor of ~7).

· Lack of consideration for flood defences is not necessarily a limitation as their future economic viability is questionable due to continued damage.

· The Portsmouth analysis produced reasonable results, clearly displaying the potential impacts associated with each scenario.

· The bathtub method used produced unrealistic results for the Hull case study as a result of known disadvantages associated with the simplistic model.

· High resolution DEM’s are necessary to increase the accuracy of flood modelling.

· Brown S, Nicholls RJ, Vafeidis A, Hinkel J, and Watkiss P (2011). The Impacts and Economic Costs of Sea-Level Rise in Europe and the Costs and Benefits of Adaptation. Summary of Results from the EC RTD ClimateCost Project. In Watkiss, P (Editor), 2011. The ClimateCost Project. Final Report. Volume 1: Europe. Published by the Stockholm Environment Institute, Sweden, 2011.

· Lowe, J. A., Howard, T. P., Pardaens, A., Tinker, J., Holt, J., Wakelin, S.,Milne, G., Leake, J., Wol , J., Horsburgh, K., Reeder, T., Jenkins, G., Ridley, J.,Dye, S., Bradley, S. (2009), UK Climate Projections science report: Marine and coastal projections. Met Office Hadley Centre, Exeter, UK.

· Ntslf.org, (2016). Chart datum & ordnance datum | National Tidal and Sea Level Facility. [online] Available at: http://www.ntslf.org/tides/datum [Accessed 2 Feb. 2016].

· Wahl, T., Jensen, J., Frank, T. & Haigh, I. (2011). Improved estimates of mean sea level changes in the German Bight over the last 166 years. Ocean Dynamics, 61, 701-715.

· RIBA & ICE. (2009). Facing up to rising sea-levels: retreat? defend? attack? The future of our coastal and estuarine cities. Royal Institute for British Architects, London, UK & Institute of Civil Engineers.