Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 7/23/2003
Publication Date: 11/2/2003
Citation: WILSON, G.V., DABNEY, S.M., SHIELDS JR, F.D. SUBSURFACE FLOW AND EROSION INDUCE STREAMBANK FAILURE. AGRONOMY ABSTRACTS. 2003. Interpretive Summary:
Technical Abstract: Field observations have shown that up to 85% of the sediment leaving a watershed may be from streambank failure. Perched water tables can result in rapid subsurface lateral flows that contribute significantly to streamflow generation, but the contribution of subsurface flow to streambank failure is not well known. Subsurface flow through unconsolidated, permeable layers results in erosion of the material at the face of streambank leaving the bank undercut and susceptible to failure. The objective of this study was to quantify the soil physical properties and hydrologic conditions associated with subsurface flow and erosion that results in streambank failure. Subsurface flow and erosion was quantified using lateral flow collection pans placed against exposed faces of the Little Topashaw Creek streambank. This stream, typical of streams in the Yazoo Basin, is characterized by "flashy" hydrology with steep banks that are prone to failure. Numerous streambank locations were identified in which a highly permeable, unconsolidated sand layer occurred above a water-restricting clay horizon. Seeps were identified at several of these locations and undercut banks due to subsurface flow erosion. Pans were permanently installed at one location at five depths in duplicate for a total of 10 pans. Pans consisted of a 100 cm by 36 cm collection area with sides inserted 15 cm into the bank face. Water collected by the pans was routed to sealed collection vessels where the volume of flow was recorded and sediment samples collected. Alternatively, subsurface flows were measured at several seep locations following selected events by temporarily installing 50 cm long flow-collection pans. The physical properties of soil profiles that exhibited subsurface flow-induced erosion were characterized. These data will be used to model the subsurface flow-surface flow interaction.