Geomorphic response of channel systems to recent climate change in the Ozark Highlands

Keywords: Fluvial geomorphology, climate change, flood impacts, channel widening, Ozark Highlands
Abstract Type: Paper Abstract

Abstract

Many rivers in the Ozark Highlands of Missouri have experienced higher flood magnitude and frequency due to more intense rainfall since the 1970s. Annual maximum discharges with recurrence intervals from 2- to 100-years have increased by 10-50% at many river gage locations. In most cases, the largest flood responses have occurred in forested watersheds and even some with improved land use. It is well understood that there is a strong relationship between channel form and flood regime. Fluvial theory predicts that the sustained occurrence of larger floods should result in channel enlargement and sediment redistribution. This study evaluates this hypothesis by examining the effects of recent flood activity on channel geomorphology. Channel widening, increased bar activity, and fine sediment deposition were observed in river segments affected by more energetic floods. Leading edge responses to climate-related flooding included increased bank erosion rates and gravel loads. In some rivers, increased peak stream power led to the erosion of coarse bed substrates such as riffles and lag boulders. If flood trends persist, it is reasonable to expect that adjustments in channel form and sediment transport will continue to occur and possibly deepen, thus potentially further degrading aquatic habitats. However, it is not clear if a change in geomorphic state is indicated for river channels in the Ozark Highlands