CALCULATED CHANNEL HEAD LOCATION AS A FUNCTION OF ELEVATION MODEL RESOLUTION

The channel head can be defined as the place where water on a hillslope first flows through definable banks and transitions into a channel. According to previous work-- which mostly used coarse resolution digital elevation models-- variables such as climate, lithology, and slope control channel head placement. However, little work has been done to quantify the effects of glaciation or elevation model resolution on calculated channel head placement. We compare channel head initiation in previously glaciated and non-glaciated landscapes of the northern Sierra Nevadas at multiple spatial resolutions. We determined flow accumulation and slope data for each site using 1-meter resolution lidar elevation models and then resampled the lidar data to find these values at 10-meter and 30-meter resolutions, which are typical of USGS and SRTM resolutions. We used the slope and drainage area values to calculate the critical drainage area-- the area at which hillslope morphology transitions to the channel head-- and analyzed the differences in this value between the sites and different resolutions. We then followed the same method at a site in southern Indiana using 10 cm, ⅓ arcsecond, and 1 arc second resolutions and we used an RTK GPS to ground truth our remote analysis of this site. Results thus far have shown that the channel head location occurs both closer to the ridgeline and at a lower slope at the glaciated site compared to the fluvial site. Within the same study site, the different DEM resolutions cause a shift in the perceived critical drainage area by an order of magnitude. These results imply that glaciation impacts stream initiation and channel head location. Moreover, it is clear that DEM resolution also affects the perceived critical drainage area. Given the different physics at play between hillslope and fluvial processes, identifying the limitations of locating channel heads has important implications for understanding the underlying processes that set landscape architecture.