HR: 08:45h
AN: H51H-04    [Abstracts]
TI: Dynamic Surface Connectivity in Semi-Arid Areas: Consequences for Water and Sediment Redistribution.
AU: * Saco, P M
EM: patricia.saco@newcastle.edu.au
AF: Civil and Environmental Engineering School of Engineering The University of Newcastle , University Drive, Callaghan, NSW 2308, Australia
AU: Willgoose, G R
EM: garry.willgoose@newcastle.edu.au
AF: Civil and Environmental Engineering School of Engineering The University of Newcastle , University Drive, Callaghan, NSW 2308, Australia
AB: We analyze the dynamics of surface (runoff) connectivity patterns in semi-arid areas with patchy vegetation. The surface connectivity pattern emerges from the interaction between hydrology, vegetation and erosion. This interaction leads to the development of a spatially variable infiltration field with low infiltration rates in the bare soil areas (due to surface crusting) and high infiltration rates in the vegetated areas (due to improved soil aggregation and macroporosity). We use a modeling framework that couples a landform evolution model with a dynamic vegetation model for water-limited ecosystems. The model captures the dynamics of spatially variable infiltration rates that are responsible for the development of a runoff-runon system, which determines the surface connectivity of the landscape and modulates the resulting sediment erosion and depositional areas. The amount of water and sediments retained by the landscape is related to the dynamic surface connectivity between the upstream and downstream areas. We analyze and compare the patterns of surface connectivity resulting from different initial topographies for hillslopes with varying slope gradients and soil erodibilities. Modeled results agree with experimental observations suggesting that, in disturbed hillslopes, there is a threshold of slope gradient below which runoff and erosion will eventually return to pre-disturbance levels and above which runoff and erosion will remain higher. In addition, we found that this threshold is related to both soil erodibility and vegetation type, which determines the dynamics of surface connectivity patterns. The principles of this dynamics have important consequences for the co-evolution of vegetation cover, hydrology and erosion patterns in arid zones, as changes in surface connectivity can lead to an irreversible loss of resources (water, soil, and nutrients) and to the desertification of these semi-arid areas.
DE: 1719 Hydrology
DE: 1813 Eco-hydrology
DE: 1815 Erosion
DE: 1825 Geomorphology: fluvial (1625)
DE: 1826 Geomorphology: hillslope (1625)
SC: Hydrology [H]
MN: 2007 Joint Assembly