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Page 1: Hydraulic Engineering and Sediment Transport...2019/05/08 ย ยท Sediment transport L h ๐‘Šsin๐›ผ ๐‘Š ฮฑ ๐œ=๐œŒ๐‘”โ„Ž๐ผ Bedload transport: (eg. Meyer-Peter and Mรผller, 1948)

Hydraulic Engineering and Sediment TransportUniv.Prof. DI Dr. Helmut Habersack

DI Dr. Mario Klรถsch

University of Natural Resources and Life Sciences (BOKU), Vienna

Page 2: Hydraulic Engineering and Sediment Transport...2019/05/08 ย ยท Sediment transport L h ๐‘Šsin๐›ผ ๐‘Š ฮฑ ๐œ=๐œŒ๐‘”โ„Ž๐ผ Bedload transport: (eg. Meyer-Peter and Mรผller, 1948)

โ€ข Introduction to sediment transport and river morphology

โ€ข Historic mophology of the Mur River

โ€ข Human impacts and consequences

โ€ข Hydraulic Engineering in the Basic Water Management Concept

โ€ข Pilot measure Gosdorf

โ€ข Monitoring of hydromorphology and verification ofconsiderations in the Basic Water Management Concept

โ€ข Conclusions

โ€ข Outlook

Content

Page 3: Hydraulic Engineering and Sediment Transport...2019/05/08 ย ยท Sediment transport L h ๐‘Šsin๐›ผ ๐‘Š ฮฑ ๐œ=๐œŒ๐‘”โ„Ž๐ผ Bedload transport: (eg. Meyer-Peter and Mรผller, 1948)

Grotzinger & Jordan (2017)

Weathering Erosion

Transport

Sedimentation

Subsidence

Diagenesis

Sediment cycle

Page 4: Hydraulic Engineering and Sediment Transport...2019/05/08 ย ยท Sediment transport L h ๐‘Šsin๐›ผ ๐‘Š ฮฑ ๐œ=๐œŒ๐‘”โ„Ž๐ผ Bedload transport: (eg. Meyer-Peter and Mรผller, 1948)

Sediment transport

L

h

๐‘Š sin๐›ผ

ฮฑ๐‘Š

๐œ = ๐œŒ๐‘”โ„Ž๐ผ

Bedload transport:(eg. Meyer-Peter and Mรผller, 1948)

Bed level change: (Exner-equation)

๐‘ž๐‘  = 8๐œŒ๐‘  โˆ’ ๐œŒ

๐œŒ๐‘”๐‘‘3

๐œ

๐œŒ๐‘  โˆ’ ๐œŒ ๐‘”๐‘‘โˆ’ 0.047

32

Bed shear stress:

๐›ฟ๐œ‚

๐›ฟ๐‘ก=

1

๐‘› โˆ’ 1

๐›ฟ๐‘ž๐‘ ๐›ฟ๐‘ฅ

Degradation or Aggradation

Page 5: Hydraulic Engineering and Sediment Transport...2019/05/08 ย ยท Sediment transport L h ๐‘Šsin๐›ผ ๐‘Š ฮฑ ๐œ=๐œŒ๐‘”โ„Ž๐ผ Bedload transport: (eg. Meyer-Peter and Mรผller, 1948)

Sediment supply and river morphology

Church (2006)

Sediment supplydeterminesmorphology

Page 6: Hydraulic Engineering and Sediment Transport...2019/05/08 ย ยท Sediment transport L h ๐‘Šsin๐›ผ ๐‘Š ฮฑ ๐œ=๐œŒ๐‘”โ„Ž๐ผ Bedload transport: (eg. Meyer-Peter and Mรผller, 1948)

Sediment supply and river morphologyโ€ฆ and determines slope

increased supply

decreased supplyaggradation

degradation

Slope adjustment via aggradation/degradation

Page 7: Hydraulic Engineering and Sediment Transport...2019/05/08 ย ยท Sediment transport L h ๐‘Šsin๐›ผ ๐‘Š ฮฑ ๐œ=๐œŒ๐‘”โ„Ž๐ผ Bedload transport: (eg. Meyer-Peter and Mรผller, 1948)

Historic state of border Mura

2km

1821-1836

Page 8: Hydraulic Engineering and Sediment Transport...2019/05/08 ย ยท Sediment transport L h ๐‘Šsin๐›ผ ๐‘Š ฮฑ ๐œ=๐œŒ๐‘”โ„Ž๐ผ Bedload transport: (eg. Meyer-Peter and Mรผller, 1948)

Historic state of border MuraBefore rockslide near the village of Vratja vas in 15th century

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Human impacts and consequencesSystematic channelisation (late 19th century)

Uniform width of 76m at low flow condition

Benefits:

โ€ข Protect from damages from channel shifts

โ€ข Gain land for agricultural use

โ€ข Protect inlet structures for canals for diverse industrial uses

Hochenburger (1894)

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Human impacts and consequences

2km

1821-18362006

Page 11: Hydraulic Engineering and Sediment Transport...2019/05/08 ย ยท Sediment transport L h ๐‘Šsin๐›ผ ๐‘Š ฮฑ ๐œ=๐œŒ๐‘”โ„Ž๐ผ Bedload transport: (eg. Meyer-Peter and Mรผller, 1948)

Wagner et al. (2015)

Human impacts and consequencesReduction of sediment supply due to a chain of hydropower plants and torrent control

Hydropower plant Obervogau (Mur River) in a chain of hydropower plants, and plant Retznei affecting sedimentsupply from Sulm River catchment

ยฉ google earth

Page 12: Hydraulic Engineering and Sediment Transport...2019/05/08 ย ยท Sediment transport L h ๐‘Šsin๐›ผ ๐‘Š ฮฑ ๐œ=๐œŒ๐‘”โ„Ž๐ผ Bedload transport: (eg. Meyer-Peter and Mรผller, 1948)

Human impacts and consequencesChannelisation:

โ€ข Increase of radius of river bends

โ€ข Increase of slope

โ€ข Decrease of width

18171876

18171876

1 km

IST-Zustand

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straight

Habersack, 2013

Human impacts and consequencesChange of morphological type

Historic Mur River

Channelised Mur River

Page 14: Hydraulic Engineering and Sediment Transport...2019/05/08 ย ยท Sediment transport L h ๐‘Šsin๐›ผ ๐‘Š ฮฑ ๐œ=๐œŒ๐‘”โ„Ž๐ผ Bedload transport: (eg. Meyer-Peter and Mรผller, 1948)

219

220

221

222

223

224

225

226

227

228

-10 10 30 50 70 90

Stationierung [m]

Hรถ

he [

m รผ

. A

.]

1981

1986

1989

1995

2000

2006

Profil km 114.840

Tertiรคr

Quartรคr

Human impacts and consequencesLimited thickness of gravel layer above finer sediment

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Human impacts and consequencesRiverbed breakthrough at Salzach River

Page 16: Hydraulic Engineering and Sediment Transport...2019/05/08 ย ยท Sediment transport L h ๐‘Šsin๐›ผ ๐‘Š ฮฑ ๐œ=๐œŒ๐‘”โ„Ž๐ผ Bedload transport: (eg. Meyer-Peter and Mรผller, 1948)

The Basic Water Management ConceptCollection and analysis of data

Cross section surveys showcontinuous degradation

Page 17: Hydraulic Engineering and Sediment Transport...2019/05/08 ย ยท Sediment transport L h ๐‘Šsin๐›ผ ๐‘Š ฮฑ ๐œ=๐œŒ๐‘”โ„Ž๐ผ Bedload transport: (eg. Meyer-Peter and Mรผller, 1948)

The Basic Water Management ConceptReduction of bed shear stress: by changing slope or width?

Habersack und Schneider (2000)

Bedload transport capacity (%)

Ch

ann

el w

idth

(m)

Ch

ann

el s

lop

e(โ€ฐ

)

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The Basic Water Management ConceptMeasure types

Habersack et al. (2001)

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The Basic Water Management ConceptModelling of scenarios with the sediment transport model

Hengl et al. (2001)

Page 20: Hydraulic Engineering and Sediment Transport...2019/05/08 ย ยท Sediment transport L h ๐‘Šsin๐›ผ ๐‘Š ฮฑ ๐œ=๐œŒ๐‘”โ„Ž๐ผ Bedload transport: (eg. Meyer-Peter and Mรผller, 1948)

MeasuresPilot measure Gosdorf

โ€ข Removal of riprap from the left bank

โ€ข Excavation of a side-channel

โ€ข Supply of excavated sediment from side-channel into main channel

Page 21: Hydraulic Engineering and Sediment Transport...2019/05/08 ย ยท Sediment transport L h ๐‘Šsin๐›ผ ๐‘Š ฮฑ ๐œ=๐œŒ๐‘”โ„Ž๐ผ Bedload transport: (eg. Meyer-Peter and Mรผller, 1948)

July 2008 โ€“June 2009June 2009 โ€“December 2009

Monitoring

Repeated bed surveys

โ€ข Erosion of supplied sediment in Gosdorf reach

โ€ข Transport downstream

โ€ข (Temporary) stabilisation of bed levels

July 2008 โ€“December 2009

Bed level change

Page 22: Hydraulic Engineering and Sediment Transport...2019/05/08 ย ยท Sediment transport L h ๐‘Šsin๐›ผ ๐‘Š ฮฑ ๐œ=๐œŒ๐‘”โ„Ž๐ผ Bedload transport: (eg. Meyer-Peter and Mรผller, 1948)

Monitoring Bedload velocity

Mean grain size dm (b-axis 42mm): ~1 km per year

D90 (b-axis= 106mm): ~ 100m per year

โ€ข Decreased velocity in restored reach due to vertical mixing

โ€ข Increased velocity downstream

โ€ข Most sediment now already in the downstream part ofthe border section or transported further downstream

Page 23: Hydraulic Engineering and Sediment Transport...2019/05/08 ย ยท Sediment transport L h ๐‘Šsin๐›ผ ๐‘Š ฮฑ ๐œ=๐œŒ๐‘”โ„Ž๐ผ Bedload transport: (eg. Meyer-Peter and Mรผller, 1948)

Monitoring Bedload transport: Assessment of critical shear stress

โ€ข Measuring tracer mobility by continuous tracer surveyโ€ข Modelling shear stress at tracer locations with a 2D

hydrodynamic-numerical model

Determination of critical thresholds for transport

Page 24: Hydraulic Engineering and Sediment Transport...2019/05/08 ย ยท Sediment transport L h ๐‘Šsin๐›ผ ๐‘Š ฮฑ ๐œ=๐œŒ๐‘”โ„Ž๐ผ Bedload transport: (eg. Meyer-Peter and Mรผller, 1948)

Monitoring Quantification of bedload transport

Basket sampler measurements Calculation of bedload yield

Page 25: Hydraulic Engineering and Sediment Transport...2019/05/08 ย ยท Sediment transport L h ๐‘Šsin๐›ผ ๐‘Š ฮฑ ๐œ=๐œŒ๐‘”โ„Ž๐ผ Bedload transport: (eg. Meyer-Peter and Mรผller, 1948)

Monitoring

Simplified consideration in Basic WaterManagement Concept:

Channel widening following a simple relation, until width reached 150m (within 17 years)

Limited bank erosion

despite major flow event (> 1000 m3/s)

Measurement of riverbank erosion

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221

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230

0 20 40 60 80 100 120 140

elev

atio

n [

m a

.s.l

.]

distance [m]

Profil 1

2007 2018

220

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226

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228

229

230

0 20 40 60 80 100 120 140

elev

atio

n [

m a

.s.l

.]

distance [m]

Profil 2

2007 2018

Width increased by 10 m (uniform section) to 28 m (downstream ofnatural rock sill)

Monitoring Measurement of riverbank erosion

Limited bank erosion

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Monitoring Relevance of river curvature and sediment supplyGosdorf vs. Sicheldorf

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Monitoring Consequence: restart of riverbed incison

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Conclusionsโ€ข Disturbed sediment regime at Mur River, no input from upstream sediment deficit

โ€ข Idea of Basic Water Management Concept: Stabilise bed and supply sediment via self-dynamic widenings

โ€ข Monitoring showed stabilising effect at the beginning

โ€ข According to tracer study most tracers must have been transported near the downstream end or out of the border section

โ€ข Self-dynamic increase of channel width remained below expectations (10m to 28m erosioncompared to 150m after 15 years in Basic Water Managment Concept)

โ€ข No change of river course โ€“ no increased curvature

โ€ข Consequence: Initial stabilisiation of bed level turns back to incision

โ€ข Threat of loosing the gravel layer

โ€ข Need for action to maintain flood protection and to save and improve ecological condition

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Outlook (1) โ€ข Necessity to analyse and verify the indicated effects at all restored sites of the border Mura

โ€ข Identifying the role of individual components (supply, width, river course etc.)

โ€ข Development of a Concept for future measures, focusing on the central points:

โ€ข Sediment budget

โ€ข Bedload supply from the banks and from upstream (goal for longterm: restoration ofsediment connectivity)

โ€ข Increase channel width to promote the development of bars and other structures

โ€ข Considering optimisation of river course (curvature) to increase secondary currents and bankerosion, including instream structures

โ€ข Find optimised mix of measures in goMURra โ€“ quantity of sediment supply, size of riverbendradius and width (and related slope change)

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Outlook (2) โ€ข Methodology: Analysis of monitoring data (cross sections, low flow water levels, satellite

images (width) etc.), Application of a 3D-hydrodynamic-numerical model coupled with a sediment transport and bank erosion model to determine the effects of scenarios of measurecombination

โ€ข Implementation of pilot measure / adaptation of Gosdorf and monitoring

โ€ข Find sections with potential for corridor

โ€ข Importance of ecological evaluation of measures

โ€ข Coordination with public water supply โ€“ change of groundwater levels

โ€ข Effect for flood protection

โ€ข -> integrated river engineering approach needed

Page 33: Hydraulic Engineering and Sediment Transport...2019/05/08 ย ยท Sediment transport L h ๐‘Šsin๐›ผ ๐‘Š ฮฑ ๐œ=๐œŒ๐‘”โ„Ž๐ผ Bedload transport: (eg. Meyer-Peter and Mรผller, 1948)

THANK YOU!Helmut Habersack

[email protected]

Institute of Hydraulic Engineering and River Research

University of Natural Resources and Life Sciences, Vienna