ARS | Publication request: Terrestrial laser scanning for delineating in-stream boulders and quantifying habitat complexity measures

Submitted to: Photogrammetric Engineering and Remote Sensing
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 7, 2011
Publication Date: April 1, 2012
Citation: Resop, J.P., Kozarek, J.L., Hession, W.C. 2012. Terrestrial laser scanning for delineating in-stream boulders and quantifying habitat complexity measures. Photogrammetric Engineering and Remote Sensing. 78(4):363-371.

Interpretive Summary: Stream restoration projects have significant economic impact, with the U.S. spending a billion dollars annually on projects to improve stream quality. One method used by stream restoration researchers to evaluate the health of aquatic species such as fish is to measure the complexity of stream habitat. Habitat complexity is commonly defined by the existence of rocks and wood within the stream to provide habitat for fish. However, habitat complexity can be difficult to measure because existing approaches are not sophisticated or accurate enough. Measurements for a brook trout stream in Virginia were taken with two different types of technologies: traditional methods and a new method that measures the stream’s physical characteristics with a higher level of detail. A computer program was developed to analyze measurements from the new technology and was used to more accurately predict habitat complexity as compared with traditional methods. The results show how utilizing the new approach can potentially provide automated and improved estimates of stream complexity, which in turn could lead to better estimates of stream quality. The results will be of use for ecological engineers, scientists, and natural resource practitioners interested in maintaining the quality of our lakes and streams.

Technical Abstract: Accurate stream topography measurement is important for many ecological applications such as hydraulic modeling and habitat characterization. Habitat complexity measures are often made using total station surveying or visual approximation, which can be subjective and have spatial resolution limitations. Terrestrial laser scanning (TLS) can measure topography at a high resolution and accuracy. Two methods, total station surveying and TLS, were used to measure a 100-m forested reach on the Staunton River in Shenandoah National Park, VA. The TLS dataset was post-processed to remove vegetation and create a 2-cm digital elevation model (DEM). An algorithm was developed for delineating rocks within the stream channel from the DEM. Ecological metrics based on the structural complexity of the stream, such as percent in-stream rock cover, were derived from the TLS dataset for six habitat areas and compared with the estimates from traditional methods. TLS has the potential to quantify habitat complexity measures in an automated, unbiased manner.