HR: 09:30h
AN: H41A-07    [PDF]
TI: Estimating Geomorphically Effective Rainrates from Elevation Data
AU: * Peckham, S D
EM: Scott.Peckham@colorado.edu
AF: INSTAAR, Univ. of Colorado, 1560 30th Street Campus Box 450, Boulder, CO 80309-0450 United States
AB: The concept of a geomorphically effective rainrate is central to many fluvial landscape evolution models, but a precise definition of this concept has proven elusive. This rainrate must be large enough for critical shear stresses to be exceeded but must also persist for long enough to significantly alter the landscape. It is often associated with the bankfull discharge. A new inverse method has been developed for estimating this effective rainrate from elevation data for mature, fluvial landscapes. This method is based on a mathematical description of mass conservation for water flowing over a landscape in the direction of the water surface gradient and on a slope-discharge relationship. The slope-discharge relationship only needs to be first-order accurate, and is an immediate consequence of two famous formulas for the hydraulic geometry of mature landscapes that have been shaped primarily by fluvial processes. Combining these facts and applying them to each element in a triangular or rectangular grid results in a topographically-derived metric that can serve as an estimator for the geomorphically effective rainrate over that cell. This metric was tested on simulated fluvial landscapes as well as on several closed-form solutions to a steady-state fluvial landscape model and it performed remarkably well. While previous results by the author showed how effective rainrates could be derived from the spacing and slope of periodic gully features such as roadcuts, this new result provides an estimate for each grid cell in a fluvial landscape. It therefore makes it possible to examine the possible variation in effective rainrates throughout basins due to orographic and other effects.
DE: 1625 Geomorphology and weathering (1824, 1886)
DE: 1815 Erosion and sedimentation
DE: 1824 Geomorphology (1625)
DE: 1860 Runoff and streamflow
SC: Hydrology [H]
MN: 2003 Fall Meeting