Exploring channel initiation thresholds across varying resolutions of topography and DEM creation techniques
Abstract
Considerable effort over the last decade has focused on describing and quantifying transport laws and landscapes processes through the use of digital elevation models (DEM). Although an invaluable tool in many studies, DEM resolution must be applied appropriately in order to adequately characterize the landscape process or response of interest. In the case of channel initiation, several studies have documented a deviation from fluvial slope-area scaling relationships at drainage areas of approximately 0.1 km2, representing a threshold at which hillslope/mass wasting processes begin to dominate. In this study, we revisit the concept of channel initiation thresholds by analyzing slope-area relationships for a set of channels in southern California using DEMs of varying spatial resolutions: 30 m (SRTM), 2.5 m (stereo-pair SPOT), 1 m (stereo-pair airphotos, NAPP), and 10 cm (terrestrial LiDAR) resolution DEMs. We analyzed the following aspects: 1) the variability in slope-area scaling between different spatial resolutions; 2) the spatial artifacts associated with decreasing resolution DEMs; 3) the complexity of channel/hillslope transitions as evidenced by ultra high-resolution terrestrial LiDAR scanning; and 4) the impact of lithology and vegetation on channel formation. Preliminary results indicate SPOT- DEM creation appears to be extremely flawed in terrain marked by abundant trees resulting in shadows and thus is unsuitable for DEM analysis in vegetated areas. We find that DEMs created from high quality, stereo-pair airphotos result in an effective and fast way to create accurate, realistic DEMs at the channel initiation scale in our study area. Lastly, thresholds for channel initiation are rarely characterized by single breaks in slope-area scaling and seem to be characterized more by complex diffuse breaks in slope-area space even in the highest reolution DEM.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.H53B1022F
- Keywords:
-
- 1804 Catchment;
- 1855 Remote sensing (1640)