HR: 0800h
AN: H51C-1140    [Abstracts]
TI: Vegetation modulated landscape evolution: Effects of vegetation on landscape processes, drainage density and topography
AU: Bras, R L
EM: rlbras@mit.edu
AF: Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 United States
AU: * Istanbulluoglu, E
EM: erkan@mit.edu
AF: Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 United States
AB: Topography acts as a template for numerous landscape processes that includes hydrologic, ecologic and biologic phenomena. These processes not only interact with each other but also contribute to shaping the landscape as they influence geomorphic processes. We have investigated the effects of vegetation on known geomorphic relations, thresholds for channel initiation and landform evolution, using both analytical and numerical approaches. Vegetation is assumed to form a uniform ground cover. Runoff erosion is modeled based on power function of excess shear stress, in which shear stress efficiency is inversely proportional to vegetation cover. Plant effect on slope stability is represented by additional cohesion provided by plant roots. Vegetation cover is assumed to reduce sediment transport rates due to physical creep processes (rainsplash, dry ravel, and expansion and contraction of sediments) according to a negative exponential relationship. Vegetation grows as a function of both available cover and unoccupied space by plants, and is killed by geomorphic disturbances (runoff erosion and landsliding), and wildfires. Analytical results suggest that, in an equilibrium basin with a fixed vegetation cover, plants may cause a transition in the dominant erosion process at the channel head. A runoff erosion dominated landscape, under none or loose vegetation cover, may become landslide dominated under a denser vegetation cover. The sign of the predicted relationship between drainage density and vegetation cover depends on the relative influence of vegetation on different erosion phenomena. With model parameter values representative of the Oregon Coast Range (OCR), numerical experiments conducted using the CHILD model. Numerical experiments reveal the importance of vegetation disturbances on the landscape structure. Simulated landscapes resemble real-world catchments in the OCR when vegetation disturbances are considered.
DE: 1815 Erosion and sedimentation
DE: 1824 Geomorphology (1625)
DE: 1848 Networks
DE: 1851 Plant ecology
DE: 1866 Soil moisture
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting