Flood defence systems in urban areas

Prof. drs ir J.K. Vrijling dr ir B. Stalenberg Section of Hydraulic Engineering Faculty of Civil Engineering and Geosciences Delft University of Technology

Land below sea level

Developments

• climate changes

• higher discharges

• more extreme storms

• sea level rise

• sinking of soil

Nature

Developments

•climate changes

•higher discharges

•more extreme storms

•sea level rise

•sinking of soil

• larger population → higher density

• more companies

• more infrastructure

result: higher value of the area

Nature Civilisation

Developments

• climate changes

• higher discharges

• more extreme storms

• sea level rise

• sinking of soil

• larger population → higher density

• more companies

• more infrastructure

result: higher value of the area

Nature Civilisation

Current tendency

increasing risk aversion

Flood protection

• strengthening of the flood defences

• reducing the loads

• strengthening of the sea defences

• reducing the loads → difficult

River Sea

Reducing the loads

• closing the estuary

• lowering of the floodplain

• deepening of the riverbed

• lowering of the groyne

• dike realignment

• flood way alias green river

• side channel

• retention areas

Outside the dike Inside the dike

Historical development in the Netherlands

Dike cross section

• Sea dike

• High waves

• Short duration

• Salt water (no grass cover)

• Estuary dike

• River dike

• Small waves

• Long duration

• Fresh water (grass cover)

Dike cross section sea dike

Sub-soil

1:6 or 8 1:3

Grass cover revetment

core Clay layer

Dike cross section estuary dike

Sub-soil

1:6 1:3

Grass cover revetment

core Clay layer

Dike cross section river dike

Sub-soil

1:2 1:3 1:4

Grass cover

core

Clay layer

Dike cross sections

• Relation dike design and failure mechanisms

Failure- mechanisms

Damming estuaries

“River” dam

System:

• Dam

• Discharge sluice

• Shipping lock

Function: • Prevent flooding by storm surges

• Shorten Coastline

• Limit salt intrusion

• Preserve fresh water

• Discharge river flow

• Let shipping pass

Many instances: • 1270 Amster dam

• 1240 Rotter dam

• 1248 Spaarn dam Zwammer dam

• ~ 1300 Monnicken dam

• ~ 1300 E dam Alblasser dam

• 1258 Schie dam

http://upload.wikimedia.org/wikipedia/commons/4/42/Map_of_Amsterdam_-_Amstelodami_Celeberrimi_Hollandiae_Emporii_Delineatio_Nova_%28J.Blaeu%2C_1649%29.jpg

1916

Enclosure dike Zuiderzee 75 years old

Enkhuizen

Floodwalls on the quay

Delta Project 1960

Storm surge barrier Eastern Scheldt

System:

• Dams

• Storm surge barrier

• Shipping lock

Function: • Prevent flooding

• Preserve environment (nature and culture)

• Preserve shell fish industry

• Let shipping pass

• Road connection

“Closed and open at the same time”

Opening ceremony 1986 & functioning

Zierikzee

Damming the lauwerszee

• Recreational park

• Port cities restored

Cardiff Bay Barrage system

Cardiff Bay mudflats before the barrage was built

Cardiff Bay Barrage system

Trends in functions

• Flood protection

• Land reclamation

• Fresh water preservation

• Facilitate shipping

• Protect environment:

• Create environment:

• Create amenity

Damming Rijnmond

• Taming water in Rijnmond

• Safety and urban waterfront development

Waterfront Dordrecht

Utrecht on de Old Rhine

Open/gesloten Rijnmond Beweegbare kering

Waterslot

Flood defences

• specific dimensions: height and width

• location

• costs

examples: dikes, quay walls

Characteristics

Strengthening

• heightening

• widening

Urban flood defence

Green river

Green river

l

Q0

Q1

Q0

Q

Q

he1h0

x0

x

Green river: adaptation length

l

Q0

Q1

Q0

Q

Qh

hhe1

h0

x0

x

Green river: sedimentation

l

Qgr,t=0hgr,t=0

hgr,t>0 Qgr,t>0

l

A green river becomes less effective in time

Current issue

reducing the loads strengthening of the flood defences

limited space

nature development only losses ?

Multi-functional flood defences

• safety

• maintenance

• property rights

• surroundings

reckon with

future strengthening

• technical issues

• legal issues

Simple examples of multiple use

• Automatic floating wall (Kampen)

• Houses built in flood defence (Dordrecht)

• Westkeetshaven (Zwijndrecht)

Automatic floating wall (Kampen)

Houses in flood defence (Dordrecht)

Westkeetshaven (Zwijndrecht)

Possibilities of multiple use

SSL

SWL

houses

offices

shops

restaurants/cafes

traffic road

parking

promenade

city park

Possibilities of multi use

SSL

SWL

traffic road

parking

shops promenadepromenade

houses

Sea defence

Possibilities of multi use De Muralt muur

SSL

SWL

Possibilities of multi use

SSL

SWL

houses

offices

shops

restaurants/cafes

traffic road

parking

promenade

city parkSSL

SWL

Possibilities of multi use

houses

restaurants/cafes

parking

SSL

SWL

Conquering the sea again

• Completed plan “IJmuiden”

• Plan “Waterman” et al.

• Plan “New Venice”

Plan “IJmuiden”

Plan “Waterman et al.”

Venice

Venice city in a shallow sea

Plan “New Venice”