An Integrative Conceptualization of Floodplain Storage

Abstract

Floodplains perform diverse functions, including attenuation of fluxes of water, solutes, and particulate material. Critical details of floodplain storage including magnitude, duration, and spatial distribution are strongly influenced by floodplain biogeochemical processes and biotic communities. Floodplain storage of diverse materials can be conceptualized in the form of a budget that quantifies inputs, outputs, and storage within the floodplain control volume. The floodplain control volume is here defined as bounded on the inner edges by the banks of the active channel(s), on the outer edges by the limit of periodic flooding and the deposition of fluvially transported sediment, on the underside by the extent of hyporheic exchange flows and the floodplain aquifer, and on the upper side by the upper elevation of living vegetation. Fluxes within the floodplain control volume can also change the location, characteristics, and residence time of material in storage. Fluxes, residence time, and quantities of material stored in floodplains can be measured directly; inferred from diverse types of remotely sensed data; or quantitatively estimated using numerical models. Human activities can modify floodplain storage by: hydrologically and/or geomorphically disconnecting channels and floodplains; altering fluxes of water and sediment to the river corridor; and obliterating floodplains through alluvial mining or urbanization. Floodplain restoration can focus on enlarging the functional floodplain, reconnecting the channel and floodplain, restoring natural regimes of water, sediment, and/or large wood, or enhancing the spatial heterogeneity of the channel and floodplain. Each form of floodplain restoration can increase floodplain storage and resilience to disturbances.