DIGITAL MONITORING OF STREAMBANK EROSION VIA LIDAR SCANNING AND GPS TECHNIQUES

New terrestrial laser scanning (TLS) and GPS technologies allow extremely accurate digital monitoring of active geologic processes. In the case of migrating stream channels, these methods can determine laterally continuous detailed distributions and rates of erosion by comparing 3D models of repeated streambank scans. Preliminary scanning studies in the Dallas - Fort Worth Metroplex have indicated streambed downcutting exceeding 1 m/decade, with similar rates of channel widening. Our study seeks to confirm these results at a nearby location, while refining and better-automating 3D model development in an active and highly vegetated riparian setting.

The previous studies were conducted on Wilson Creek, a meandering stream cutting recent alluvium within the Heard Natural Science and Wildlife Museum in McKinney, Texas. At this site results of a 1999 manual TLS streambank survey, followed by automated scans in 2009 were compared, revealing alarming rates of downcutting and channel widening. These erosion rates are orders of magnitude higher than found for typical undisturbed natural settings. While accelerated erosion is not unusual for rapidly urbanizing areas like McKinney, the observed rates may severely threaten the natural environment and near-stream engineered structures. At this time no existing or planned mitigation measures are focused on erosion control, and erosion can be expected to continue at this rate or higher while urbanization continues in the suburbs north of Dallas.

The TLS/GPS system is well suited for erosion monitoring because of its speed, since direct contact with the streambank is not required and scanner range is hundreds of meters. Our study will also address ways of improving the methodologies for field and lab operations, including automated treatment of vegetation interference, accurate geo-referencing beneath a heavy tree canopy and development of an efficient software path for 3D model generation.