US Forest Service, Rocky Mountain Research Station, Boise , Idaho
Traditional techniques for describing and understanding aquatic physical habitat in streams have focused on manual measurements of channel topography. Typically this involves field mapping techniques that can be time-consuming, costly, labor- intensive and limited to infrequent local reach-scale surveys done during low flow conditions. It can be logistically prohibitive to conduct the field surveys at spatial and temporal scales appropriate for some aquatic species. For example, an optimal sampling scheme may be to take repeated measurements at a high frequency along the channel but costs dictate seasonal data collection at select or widely separated sites.
New remote sensing techniques, such as airborne water-penetrating Light Detection and Ranging (LiDAR) and boat-mounted acoustic sensors can produce highly accurate Digital Elevation Models (DEMs) with continuous coverage of long segments of channels and stream networks. Thus, we now have the ability to more nearly inventory, rather than locally sample, the same aquatic habitats. However, we lack automated techniques to analyze these new more-synoptic digital data. The US Forest Service has contracted ESSA to develop a suite of GIS tools, the River Bathymetry Toolkit (RBT) for processing high resolution DEMs of channels. Our goal is to characterize in-stream and floodplain geomorphology to support aquatic habitat analyses and numerical models of flow and sediment transport. The (RBT) is available for free and is under active development. Tools exist for cutting cross sections and longitudinal profiles into high resolution DEMs to extract hydrologic parameters such as wetted area, bankfull width, hydraulic radius, gradient and sinuosity. It is possible to save the cross section properties as a ShapeFile and then add them to a map. Using an automated detrending algorithm we are able to remove the overall valley slope. Tools are being created that use the detrended raster to investigate flooding outside a main channel at any prescribed discharge or flow stage. These will allow us to describe the “off-channel” habitat under different flow conditions.
The US Forest Service, Rocky Mountain Research Station also maintains a website dedicated to their River Bathymetry Toolkit research project.