Sediment in streams is a natural phenomenon, however too much sediment leads to impairment of stream and receiving coastal ecosystems. We can measure the amount of sediment in a stream without too much difficulty. The challenge is determining the sources of that sediment. GIS, in conjunction with geospatial data sources, may provide another means of answering the ‘source’ question and directing regulatory and management efforts to more efficiently manage sediment pollution in our waterways. The project will involve finding the difference between two separate, LiDAR-derived DEM data layers characterizing land surface topography at two separate points in time, to assess changes in soil and sediment storage across an entire watershed. Part of this work may involve going back to the raw, point-cloud data to develop unique DEM products. There is also a question of how well DEMs from separate time periods will ‘line up’. We are also interested in investigating additional analyses related to these data, such as changes in stream channels over time for an entire stream network.
The White Clay Creek watershed will be the focus given its long history as the primary research watershed for the Stroud Water Research Center. We currently have (know of) two LiDAR-derived DEM data layers covering the White Clay Creek watershed in SE PA. The first set comprises two separate data collection flights in April (leaf off) and July (leaf on) 2010. The point cloud data and derived raster product(s) are available along with applicable metadata: http://opentopo.sdsc.edu/datasetMetadata?otCollectionID=OT.102011.26918.2. The second set of data is available through the USGS MD/PA Sandy Supplemental Lidar Data Acquisition and Processing Production Task. The time period for these data is December 2014 and January 2015, depending upon the specific data tile. Data and associated metadata for MD/PA geographies are available at http://www.pasda.psu.edu/ (can search by Provider = U.S. Geological Survey or by Keyword = Sandy Lidar).
If successful, the deliverables for this project would be two-fold: (1) A map showing areas of soil/sediment loss and gain, not just along the stream network, but over the entire land area draining to the stream network (i.e. watershed); and (2) quantifying the amount of sediment moving to and through a stream network based on the difference in DEM-defined elevations, for two points in time, across a landscape. If the fellow also analyses changes in stream channels, the deliverables would be a map or series of maps showing these changes accompanied by the generated data.
Maps will be used to show the potential, landscape-based sources of sediment in streams by showing where the differences in DEM-defined elevations primarily occur: along stream reaches (‘riparian’ areas) versus in the upland portions of a watershed. The differences in DEM-based elevations will also lead directly to estimates of sediment moving into and through stream networks that can be compared to other estimates, whether from direct sampling of streams or through various models of stream sediment dynamics. The project results will inform and influence policy at the state and federal levels regarding best practices to achieve compliance with TMDL (Total Maximum Daily Load) and MS4 (Municipal Separate Storm Sewer Systems) regulations that seek to limit negative impacts on stream water quality and coastal ecosystem function.
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