A topographic fingerprint to distinguish alluvial fan formative processes

We demonstrate here a topographic fingerprint, derived from a 1 m high-resolution elevation model (DEM), developed from Airborne Laser Swath Mapping (ALSM) that distinguishes between formative processes from surface form in alluvial fans generated through relatively dry debris flows (DF) and those surfaces formed primarily by fluvial sediment transport (ME). We selected alluvial fans with primarily Holocene age surficial deposits along the eastern side of Death Valley, California. Fans were initially classified in the field into DF and ME types, largely on the basis of sedimentological characteristics and surface morphometry. Trend surface analyses were performed on DEMs of the individual fans in order to remove the long-wavelength trends (both profile and planimetric). From the residual data, we found that high-resolution surface data distinguishes process information in two ways; 1) local-relief increases as a function of length-scale, especially at length scales less than 40-60 m, and 2) local-relief is significantly higher for debris-flow dominated fans than for fluvially dominated fans. This fingerprint, which is directly related to the dominant surface processes, is unavailable from standard 30 m resolution data, providing significant support for the acquisition of high-quality high-resolution data. This fingerprint can be used to help calibrate numerical simulations of alluvial fan development, and has the potential for similar applications to distinguish between processes of similar landforms on other planetary bodies within our solar system. (C) 2006 Elsevier B.V. All rights reserved.