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Morphological challenges: morphological impact resulting from the demands of the individual interests.

RESTORE – WORKSHOPPart 1

Sharing River restoration knowledge and experience in Europe,

Iaşi-ROMANIA, 9-11 May 2012

Hendrik Havinga

Rijkswaterstaat Oost NederlandDutch Ministry of Infrastructure and Environment

River restoration topics

• Goals (increase bio-diversity, WFD)• River functions• Current situation (natural river, regulated river, physics)• Restoration measures problems (challenges..)• Mitigating measures• Monitoring• Maintenance• Administration processes

The river and its user functions

Primary function

Added functions

Regulated River

The Waal River, NL

Bridge upstream city of Kampen, 1996

The Primary function(safe discharge of water, ice and sediment)

Discharge control at Pannerden Weir1993 flood in Waal River at Kekendom

Sedimentation in branch of Yangtze River in Dongting area

New levee after breach, Dongting Lake , 1998

Added functions

Current situation, Rhineexample

• Historical developments• Today

Istein

Rhine River catchment

The Oberrhein in early days...(at Istein)

Basel

View at Istein today..

Restrhein +

Canal d’Alsace

The OberrheinregulationR

egul

erin

g

River regulation German Oberrhein

Johan Gottfried Tulla

River training: also closing of side channels

Dike failure through ice dams(may very well start on shoals, at side

channel inlets)

River Regulation Measures

Measure Hydromorphological effect

Singular groynes (jetties) Width reductionDikes (Levees) “Normalisation “Bend cut-off River shorteningLocks and dams Sediment withdrawalDeforestation Sediment supply

leveegroyne

summerdikefairwayfloodplain

The regulated river

Why this lay-out ?

LAY-OUT PREFERENCES

Interest Geography Defenses HydrologySAFETYAG AINSTFLOODING

Summer dikesWinter dikesGroynes (ice)

"armoured"

rock

guarding max. design water-levels and dischargedistributions

NAVIGATION summer dikesDeep minor bed

"armoured"constructionsrock

up to 4,0 m waterdepth:total discharge through minorbed.

AGRICULTURE summer dikespolder dikesgrassno naturalvegetation

"armoured" no flooding

ECOLOGY summer dikes withinlets and outletssecondarychannelsNatural vegetation

"soft"constructionsno rock

frequent flooding

constructions

constructions

leveegroyne

summerdikefairwayfloodplain

The regulated river

Impact of levees, dikes and groynes ?

Bed

Water level

Width reductiontop view

Flow direction

longitudinal view

Bed

Water level

short term effects of width reductiontop view

Flow direction

longitudinal view

Bed level

Water level

Final effects of width reductiontop view

Flow direction

longitudinal view

Bed

Water level

Bend cut-offtop view

Flow direction

longitudinal view

A

A

B

B

Bed

Water level

Short term effects of Bend cut-offtop view

Flow direction

longitudinal view

A

A

B

BB

Bed level

Water level

Final effects of bend cut-offtop view

Flow direction

longitudinal view

A

A

B

BB

Bed

water level

Dam in the rivertop view

longitudinal view

Flow direction

Bed

Water level

top viewFlow direction

longitudinal view

Short term effects of dam in the river

Bed level

water level

Long term effects of dam in the rivertop view

Flow direction

longitudinal view

Side-effect of regulation works: increased flood levels

8000m3/s

4000

2000

0

MaxauΔQ = 1100 m3/sΔt = - 45 hr

1 2 3 4 5 6 7 8 9 10t

Q

Maxau1882/1883

Worms1882/1883

1995

1995

Flood waveOberrhein

WormsΔQ = 1820 m3/sΔt = - 45 hr

• Dutch Rhine

Other side-effect: Bed degradation(Waal River)

sedimentation

erosion

turning pointz: 2 cm/year

dredging

Nijmegen

Erlecom

HaalderenHulhuizen

Pann. Kop

Tiel

St.-Andries

Dreumel

Gorinchem

DodewaardOchtenIJzendoorn

Ben. Leeuwen

OpijnenHaaftenHerwijnen

Zaltbommel

sea

leveegroyne

summerdikefairwayfloodplain

The regulated river

Regulation led to increase of flood levels and severe bed erosion

Also nature values have been harmed

Today’s major river projects in the Netherlands

• Room for the River Program:– Lower flood levels – Some 40 measures to increase flood conveyance (400 km)– Increase of landscape quality

• Natural vegetation, side channels– Ready in 2015– Budget € 2.3 billion

• European Water Framework Directive (WFD):– Good Ecological Potential– Only banks and floodplains can help

Overview of projectsites

Room for the River

Room for the River measures

Measures with ecological potential

WFD Project scope for central and eastern NL until 2015

95 ha floodplain lowering25 km secondary channel 2-sided 8 km secondary channel 1-sided60 km ecological river banks15 ha shallow reed zones41 fish passages

IJssel

Waal

L. Rhine-Lek

Budget 130 80 million €Postponement of measures after 2015

Many projectsExample IJssel River (120 km)

Restoration measures

Floodplains aggrade

Main channelsincise

Groynes narrow main channel and prevent lateral migration

Normalised Rivers : hydromorphologicalpressures

All large rivers are designated as heavily modifiedand can only to a limited part be rehabilitated

Types of measures for ecological improvementfor fish, macrofauna and waterplants

ThemeRestoration of habitats and natural

dynamics• Shallow areas, low flow velocity• Protected from waves from ships• Variation in conditions (substrate, flow

velocity, water depth)• Sandy banks with a gradual slope

Remove barriers for fish migration• Connect rivers and brooks• Connect fresh and marine waters

Clear and clean water

MeasureEcological banksConnecting lakes to riversConstruction of secondary channelsLowering of floodplains

Construction of fish passagesRehabilitation of mouth of brooks

Introduction of seeds of water plantsCreation of shelter by e.g. a dam

Ecological river bank

Actual

Plan

Erosion from ecologicalriver bank

Sedimentation in navigation channelConcern from navigation sectorMorphological study

Secondary channels Waal and Nederrijn-Lek

Gameren

channel AmerongseBovenpolder 5,8 km

VreugdenrijkerwaardMaintenance- Sedimentation in main and secondary channel- Vegetation

Fish passage Weirs Nederrijn

Mouth of brook

45

winde

Restore connection for fishmigration between rivers and brooks

Pumping station

Assignment

• Group divided in 4 subgroups– Discuss of your home situation, executed/planned

restoration measures and problems– Give short outline on flipoverflaps

• Results will be presented tomorrow• Possible rearrangement of content

Results of the assignment

Restoration measures problems(challenges..)

• Free banks• Side channels

Removal of bank defenses and re-introduction of side channels may present management problems

River restoration measures– Natural vegetation– Free banks – Side channels

Natural vegetation decreases flood protection

Example: longitudinal dam in groynefields (prevents erosion, increasesfairway) (Waal River near Opijnen)

Side channel through groynes = fish passage

Vegetation Development

Opijnen 1992

Vegetation Development

Opijnen 2003

Intervention and Monitoring

What is the right moment to intervene ????

Quality: flood protection level, sailing depth, stability, ecological potential,..

56

Historical bank erosion (by cattle and ships) was reason for bank protection

• Removal of rip rap, construction of new groynes

• Sandy banks, tolerated bank erosion• In time accretion in navigation

channel

photo: B. Boekhoven

IJssel Engelse werk

Removal of bank protection (right bank) at EngelseWerk (Zwolle) dynamic land-water gradient

21 m (12 m in 1995-2001)

28 m (8 m in 1995-2001)

16 m (16 m in 1995-2001)

February 2008

Engelse werk, 13 years later

Original bank

Increased morphodynamics

bank erosion by wave attack

sedimentation during flood

Initial outflanking of groynes

More various macrofauna communities

Side channel in the Klompenwaard (Waal River near bifurcation Pannerden)

Bakenhof dike set-back, Nederrijn River, 2000near bifurcation Westervoort

Impact on low water bed

First shoal

Aggradation of bend

Flood shoal Increased flood levelsHindrance to navigation

Plan Westenholte:Lowered flood plains + side channel

Morphological effects onmain channel (1/3)

elevation

(m+NAP)

flow velocity

(m/s)

gradualacceleration abrupt

deceleration

gradualdecelaration

abrupt acceleration

Morphological effects onmain channel (2/3)

flow velocity

(m/s)

gradualacceleration abrupt

deceleration

gradualdecelaration

abrupt acceleration

initial bed level changes

(m/day)

sedimentationfront

erosionsedimentation

erosionexpansion

wave

Morphological effects onmain channel (3/3)

initial bed level changes

(m/day)

elevation

(m+NAP)

erosion

sedimentationfront

sedimentationerosion

expansionwave

Gameren

Side channel(Waal River near Gameren)

Aggradation main channel as planned (2 dm, channel discharges < 3%).Local erosion at groyne roots and transfer zones undefended/defended banks

East channelWest channel

Large channel

Computed bed level respons Gameren(2 dimensional morphological model Delft3DMOR, repeated yearly hydrograph)

Deltares (former WL Delft Hydraulics, 2004)

Control principles for sidechannels

(from) MSc Study of Mr. Bhuban Ghimirestudent at UNESCO-IHE Delft (2003), titled:

“No-regret” solutions for intakes for side channels

River Waal

Secondary Channel

S control (local)

Q control (local)

X-section control (whole channel)

Quantity of Sediment Entering

Sediment Transport capacity

Channel Stability

Increasing sediment sizeIncreasing sediment size Increasing slopeIncreasing slope

Sediment loadSediment load

DegradationDegradation

Water dischargeWater discharge

AggradationAggradation

LaneLane’’s Balances Balance

Control principles..Control principles..

⎟⎟⎠

⎞⎜⎜⎝

⎛

W

sc

QQ

⎟⎟⎠

⎞⎜⎜⎝

⎛

W

sc

SS Deep

channel

Normal channel

Wide channel

Sediment transport capacities for different channel sections

CrossCross--section controlsection control

Transport capacityTransport capacity

Sediment distributionSediment distributionHydraulicHydraulic controlcontrol

⎟⎟⎠

⎞⎜⎜⎝

⎛

W

sc

QQ

⎟⎟⎠

⎞⎜⎜⎝

⎛

W

sc

SS

Sediment distribution

ΔS(Qcontrol)

⎟ ⎟

⎠

⎞

⎜ ⎜

⎝

⎛

W

scQ

Q

⎟ ⎟

⎠

⎞ ⎜ ⎜

⎝

⎛

W

scS

S

Sediment d istribution

ΔS (S control)

Sediment Sediment controlcontrol

Transp. Cap.

72

End of part 1