HR: 1330h
AN: H12D-1016    [PDF]
TI: Channel Slope From SRTM Water Surface Elevations in the Amazon Basin
AU: * Hendricks, G A
EM: ghendric@ucla.edu
AF: Department of Geography, University of California, Los Angeles, Los Angeles, CA 90095 United States
AU: Alsdorf, D E
EM: alsdorf@geog.ucla.edu
AF: Department of Geography, University of California, Los Angeles, Los Angeles, CA 90095 United States
AU: Pavelsky, T M
EM: pavelsky@ucla.edu
AF: Department of Geography, University of California, Los Angeles, Los Angeles, CA 90095 United States
AU: Sheng, Y
EM: ysheng@geog.ucla.edu
AF: Department of Geography, University of California, Los Angeles, Los Angeles, CA 90095 United States
AB: A lack of hydrologic observations exists globally, particularly for large rivers in remote, non-industrialized regions. Considering the combined global decline in gauging stations as well as a prohibitive cost in increasing gauges to a reliable number for discharge prediction, remote sensing observations are both a necessary and efficient means for measuring certain hydraulic variables. Remote sensing observations allow for an unparalleled spatial scale and consistency in temporal acquisition. The Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM) provides an initial means of measuring surface water elevations. Typically, open water flowing in channels yields specular radar pulse travel paths, however a roughened water surface can allow for partial radar return to the antennae. These water surface elevations combined with associated distances can be used to determine channel slope, which is an important component of the Manning equation and ultimately can be used to predict river discharge. Distance along each channel was extracted from the SRTM DEM by first determining flow vectors for each pixel from evaluation of the surrounding eight pixels, and then by linking the vectors. The resulting water slopes were calculated for the area from 0S-8S, 72W-54W. The Amazon mainstem was found to have a slope of 3.26 cm/km upstream of Manaus, while the slope is only 0.64 cm/km for the reach downstream of Manaus. The Tapajos slopes ranged from nearly flat near the mouth (0.29 cm/km) to a greater slope (17.57 cm/km to 11.47 cm/km) in the middle and upper reaches respectively, which are drained from a higher relief region. The Japura, Branco, Ica, and Madiera tributaries drain relatively higher relief regions and have slopes that range from 4.79 to 3.65 cm/km. The Purus and the Negro are more moderate with slopes of 3.09 cm/km and 2.47 cm/km respectively. These values are consistent with topographic relief and show that channel surface slopes can be measured on a vast spatial scale from SRTM provided that water surfaces are roughened. These slopes will be used in conjunction with depth values attained from nautical charts (for the mainstem Amazon) and width measurements obtained from classifications of JERS-1 low water data to estimate discharge of the Amazon and its major tributaries.
DE: 1848 Networks
DE: 1860 Runoff and streamflow
DE: 1890 Wetlands
DE: 1894 Instruments and techniques
SC: Hydrology [H]
MN: 2003 Fall Meeting