1. WL | Delft Hydraulics, RIZA
Impact of climate change and anticipating flood management strategy on floodplain ecosystems of the River Rhine, The Netherlands
Marjolijn Haasnoot, Harm Duel, Guda van der Lee, Martin Baptist, Diederik van der Molen, Maarten Platteeuw
WL | Delft Hydraulics, RIZA
anticipate
yes
in 1920!
But I used to be the best student
Trees will get ‘stress’

2. Introduction Dutch rivers are highly regulated by dikes and dams
Climate change will have impact on functions like agriculture, urban areas, shipping and nature
Measurements are needed: eg. more room for the river by Cyclic Flood Rejuvenation (CFR) to deal with higher discharges
 What is the impact of climate change and anticipating flood management strategy on the ecosystem of the River Rhine in the Netherlands?
history of the dutch rivers
floodplains are mainly used for agriculture (intensive grassland)
climate change  higher discharges

3. Method 1 – climate change
As a result of climate change precipitation is expected to increase. River Rhine will get higher discharges in winter and lower in summer
current situation or climate 2050
RHINEFLOW
hydrological model
river discharge
elevation map
In Dutch rivers, the combination of river rehabilitation and flood safety is conflicting, because floodplain vegetation increases the hydraulic roughness and sedimentation on the floodplains.
Therefore, there is an increasing interest in the interactions between vegetation - water flow - sediment transport and geomorphology.
New management concepts are introduced, i.e. ‘Cyclic Floodplain Rejuvenation’.
flood duration map
GIS
ecotope map
HABITAT
spatial analysis tool
habitat suitability map

4. Method II – Cyclic Flood Rejuvenation (CFR)
Natural floodplain vegetation increases the hydraulic roughness: water levels increase
CFR: recurrent removal of vegetation and sediment to guard flood safety
SOBEK 2D
hydrological model
water levels
sedimentation
Floodplain vegetation increases the hydraulic roughness of the floodplains and therefore decreases the conveyance capacity.
Natural processes to remove older vegetation, such as channel migration or ice scour, do not occur anymore in the Rhine. Consequently vegetation development can only go one way: succession to older stages.
“Cyclic Floodplain Rejuvenation” is the recurrent removal of vegetation and sediment (i) to guard flood safety and (ii) to increase biodiversity.
vegetation succesion
Every 5 years:
if critical water level is exceeded, then CFR measure. until 2050
flood duration map
ecotope map
HABITAT
spatial analysis tool
habitat suitability map

5. Effects of climate change scenarios
acreage hardwood forest, river dune, natural levee pasture decreases
acreage softwoord forest, natural levee hayfield, natural river bank increases
effect on habitats and species
hogere afvoer in winter, lagere afvoer in zomer
aantal hectares van de rjn ha
agriculture and urban areas if to wet  nature
agriculture urban areas,water not shown in this figure
total area ecotopes x 1,000 ha
for climate change in 2050

6. Effects of flood management strategy: CFR
Room for river: excavation floodplain and removal of forest (CFR)
after implementation vegetation succession: bare soil, grass- haylands to forest
effect on habitats and species

7. Change of habitat suitability for the Corn crake after CFR
years
Change of habitat suitability for the Corn crake after CFR
The breeding habitat of the Corn crake (Crex crex) is situated in grasslands that are rich in structure. Following flood prevention measures, the habitat suitability first increases. However, the grasslands will be gradually replaced by softwood forests and subsequently, the suitability will decrease again.

8. Impact climate change and CFR
change area (x 1,000 ha) suitable habitat
CFR
after implementation
CFR after 20 years
CFR after 50 years
climate change

9. Discussion
In this study we looked at indirect effects (through hydrology) of climate change. Direct effect can also be expected eg. by a rise of temperature and CO2
However, hydrology is important factor influencing habitats along rivers
More management strategies could be considered
begin groeiseizoen
competitie tussen soorten snelle en langzaam groeiende soorten
verdamping via huidmondjes

10. Conclusions
Climate change has a significant effect of ecotopes and habitats along the River Rhine
However, effects of anticipating flood management strategies, like CFR might be more important
A shift in management practice in floodplain may be very beneficial for ecological quality of the floodplains (consider time and spatial distribution)
anticipate