HR: 09:15h
AN: H11H-06    [Abstracts]
TI: Effects of Rainfall Variability on the Initiation of Preferential Flow
AU: * Tymchak, M P
EM: tymchak@geol.sc.edu
AF: University of South Carolina, Dept. of Geological Sciences, EWSC 617 701 Sumter St, Columbia, SC 29208 United States
AU: Torres, R
EM: torres@geol.sc.edu
AF: University of South Carolina, Dept. of Geological Sciences, EWSC 617 701 Sumter St, Columbia, SC 29208 United States
AB: The purpose of this study was to evaluate the effects of non-ponding rainfall variability on the initiation of preferential flow in unsaturated, forested hillslopes. To investigate this, we monitored rainfall and soil-water content response at three soil profiles on a sandy hillslope. We also conducted numerical simulations of soil-water content response to several rain events in order to compare observed and expected. Storms with highly variable, high intensity rainfall rates produced wetting fronts that accelerated with depth in one profile. Numerical simulations did not match this response. We interpret the apparent wetting front acceleration to be the result of preferential or macropore flow, and propose that highly variable, high intensity rainfall on a wet soil with non-linear soil-water retention properties may be required to trigger preferential flow in an unsaturated soil. We propose that stored capillary water may transition to free water that is associated with highly variable rainfall and a threshold in soil-water retention. Hence, our findings suggest that water flow through this soil may intermittently switch from displacement to bypass flow, and that the transition is likely governed by rainfall sequencing, or temporal variations in rainfall intensity during a single storm event.
DE: 1804 Catchment
DE: 1838 Infiltration
DE: 1854 Precipitation (3354)
DE: 1875 Vadose zone
SC: Hydrology [H]
MN: Fall Meeting 2005