HR: 1340h
AN: H13H-1403    [Abstracts]
TI: Bedrock and soil contribution to the runoff formation in a headwater catchment: experimental observations and simulation using the hydrological distributed model GEOtop
AU: * Bertoldi, G
EM: bertoldi@duke.edu
AF: Duke University, Department of Civil Engineering, CIEMAS Building Room 2417, Durham, NC 27708-0287 United States
AU: Dietrich, W E
EM: bill@eps.berkeley.edu
AF: University of California Berkeley, Department of Earth and Planetary Science, 313 McCone Hall, Berkeley, CA 94720 United States
AU: Miller, N L
EM: nlmiller@lbl.gov
AF: Lawrence Berkeley National Laboratory, 1 Cyclotron Road Builing 5, Berkeley, CA 94720 United States
AU: Rigon, R
EM: riccardo.rigon@ing.unitn.it
AF: University of Trento, Department of Civil and Environmental Engineering, Via Mesiano 77, Trento, TN 38050 Italy
AB: Most of the models used to reproduce the runoff at hillslope scale and at small-catchment scale are based on the assumption that the sub-surface runoff flows following the bedrock topography, often considered impermeable and parallel to the surface. Another common hypothesis is that the motion can be described as a function of the only topographic gradient rather than of the hydraulic head gradient. In this contribution, to assess the importance of these statements the distributed model GEOtop has been applied to a flood event in a small headwater catchment (2.3 ha) located in Marin County, California, USA. A measuring campaign has recognized a motion field where the fractured bedrock contribution appears significant. During storms, hillslopes do not saturate at the soil-bedrock interface, while a shallow water table remains in hollows also during the dry season. Simulations under different conditions (with uniform and measured soil thickness) have been performed, and different degrees of bedrock permeability have been simulated. The model makes it possible to reproduce the outgoing discharges, the saturated areas, and the observed water table in a suitable way and the results confirm the importance of considering the flow inside the bedrock to reproduce the basin response. Lastly, the model shows that a significant contribution to the saturated area is given by the potential suction gradient which forms at the interface between unsaturated hillslopes and saturated hollows, whose modelling can be neglected.
DE: 1804 Catchment
DE: 1826 Geomorphology: hillslope (1625)
DE: 1830 Groundwater/surface water interaction
DE: 1847 Modeling
DE: 1875 Vadose zone
SC: Hydrology [H]
MN: Fall Meeting 2005