Premium
Modeling effects of floods on streambed hydraulic conductivity and groundwater‐surface water interactions
Author(s) -
Simpson Scott C.,
Meixner Thomas
Publication year - 2012
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/2011wr011022
Subject(s) - clogging , hydraulic conductivity , aquifer , infiltration (hvac) , hydrology (agriculture) , flood myth , groundwater recharge , environmental science , sediment , groundwater , geology , soil science , geotechnical engineering , geomorphology , soil water , history , philosophy , physics , theology , archaeology , thermodynamics
Flood events can induce temporal changes in streambed elevation and particle‐size composition, which may influence the bed's hydraulic properties and stream‐aquifer fluxes during and after an event. This study combines a set of previously developed modeling approaches to create a synthetic flood event during which bed sediment is entrained and deposited as a function of hydraulic conditions and particle size. One simulated river reach in a state of approximate dynamic equilibrium is chosen to investigate the impacts of size‐selective sediment transport on stream‐aquifer interaction. Along this reach, the preferential entrainment of fine sediment during the flood's rising limb leads to overall bed coarsening, and increases in vertical hydraulic conductivity ( K bv ) and downward fluxes of floodwater into the streambed. Progressively finer sediment layers are deposited during the event's falling limb, causing the redevelopment of a colmation (clogging) layer on the bed surface and a decline in overall K bv by the event's conclusion. This reduction in K bv leads to prolonged retention of event water in the streambed (after the reach reverts from losing to gaining river conditions) when compared with what is expected if pre‐event K bv values are used to estimate river‐aquifer exchanges. This process of sequential bed coarsening and fining during a flood event provides a mechanistic explanation for the event size‐and‐duration threshold, inferred in some systems, that must be exceeded for significant amounts of flood recharge to occur. The major consequences of these processes—enhanced infiltration and prolonged floodwater retention—have potentially major implications for groundwater‐surface water interactions, water quality, contaminant transport, and riparian biogeochemistry.