Review Article

The Potential for Dams to Impact Lowland Meandering River Floodplain Geomorphology

Table 1

Phases of floodplain inundation and drainage as suggested by various sources, modified from [8].

SourceFlood phase

Allen (1970) [66] Spilling of flood water from the main channel into empty flood-basins Filling up of flood basins to a stage where sustained flow down the floodplain is possible Emptying of flood basinsDrying out of flood basins and modification of newly deposited sediment

Lewin and Hughes (1980) [63]Low water channelUnvegetated bars and secondary channelsGroundwater rise and areas directly connected to channel via bank breachesHigher parts of bars and breaches feeding more low relief areasBankfull promotes more rapid filling by overbank spilling and slows down the rate of stage rise in the channelInternal transfer processes extend area of inundationFloodplain filling: ponds begin to deepen rather than extendWhole valley flooded: further increments lead to higher flow velocities and depthsRiver stage falling allowing overbank returnsOnce below bankfull rate of recession depends on the efficiency of transfer processes and ebb channels to empty floodplainIsolated disconnected ponds left in topographic lows to dry by infiltration and evaporation

Zwoli ski (1992) [8] Channel and groundwaters rise: erosive modification of floodplain edges (bank erosion) Inundation of the floodplain: erosion and redeposition of older sediments; accretion of bars and levees Adjustments of the overbank flow pattern to floodplain environment (morphology, vegetation, etc); transport dominant, but accretion occurs across floodplainFlood peak: erosion declining, widespread transportInitial fall of floodwaters: changes in overbank flow pattern; reduction in erosion and transport; peak depositionGradual cessation of floodwaters; transport ceases; final deposition and erosive modification of new depositsLoss of stagnant water from depressions  
Postflood subaerial transformation of floodplain