ABSTRACT: Floodplain area-age relations and their utility in estimating long-term sediment transport rates.

CGRG Bibliography of Canadian Geomorphology
Search Results

Author :

Date :

Title :

Publication :

Issue :

Page(s) :

Abstract

Floodplains are important storage zones for alluvial sediments. Floodplains develop over time in response to varying amounts of water and sediment discharge and therefore have the potential to record changes in the rate of sediment transfer through the basin. Floodplain area-age relations for selected rivers in Canada and elsewhere are used here to establish their utility in defining the magnitude and rate of sediment exchange from the floodplain. Aerial photographs, surface vegetation including models for vegetation succession, historical records and 14C dating of floodplain sequences are used to make inferences of surface age. Using mainly the unconstrained reaches in wider sections of the valley, the proportion of total floodplain area eroded decreases with increasing age of the sediment but the functional form of the decrease changes with respect to stream power. High-energy systems, including braided and wandering river morphologies, show exponential decreases whereas low-energy systems, including meandering and anastomosed types, exhibit a mainly linear decrease. Successful prediction of long-term sediment transport rates requires specification of a stable area-age relation. Extreme events, such as floods capable of resetting river regime, disrupt the area-age relation and complicate predictions. Verification of the inferred sediment transport rates using area-age relations remains problematic because of the lack of independent evidence for long-term sediment fluxes.

Bibliography of Canadian Geomorphology