Thinking Outside the Floodplain: A LiDAR-based Tool to Assess Stream Network Connectivity

Put a group of restoration practitioners in a degraded meadow and in short order you'll find them kicking dirt around an attention-grabbing gully or head-cut discussing options for fixing them. But these features often represent symptoms of altered flow regimes rather than causes. Upstream of these scars may occur any number of source problems such as diversions, constrictions, and ditches that have been long since monumented into the landscape by roads, culverts, and levees. Here we describe a LiDAR-based streamflow analysis tool designed to expand the perspective and scope of restoration assessments and then focus attention on source problems that hold the impaired area in poor condition. We developed the tool using open-source and free software to unite high resolution terrain maps with detailed streamflow analyses through a Google Earth platform. It allows for three-dimensional exploration of watershed features color-coded by their elevational relationship to stream height. The user can easily pinpoint disturbances and disconnections in the stream network and locate the best places to rectify problems. Restoration of meadow and floodplain surfaces benefit from a watershed view of historical alterations so that we can remove these impediments to physical and biological processes that accelerate natural system recovery. An example of the tool's application is provided for the upper Deer Creek watershed, Tehama County, California.