Goerman, David, Bureau of Waterways Engineering and Wetlands, PA Dept. Environmental Protection, 400 Market St, Harrisburg, PA 17105, dgoerman@pa.gov.
The presentation will provide an overview of the remedial activities done on a large-scale floodplain reestablishment project. The project encompasses approximately 4,600 feet of floodplain valley restoration encompassing approximately 18 acres. The valley was originally buried in coal waste or culm that during events was heavily eroded and transported into the downstream communities along Good Spring Creek (GSC) and the Swatara Creek. The Donaldson Culm Bank eliminated the natural floodplain of GSC adding to the higher peak stream flows and flooding downstream in the Boroughs of Tremont and Pine Grove and Pine Grove Township Schuylkill County. A brief discussion of why intervention (aka the problems) was necessary to ensure the success of the original project objectives. A discussion of the design techniques and decisions that were made to implement this novel approach to reestablishing the 7 square mile drainage area watercourse.
The work included excavation and placement of additional log base level control structures that were buried below the floodplain surface to prevent and control any accelerated erosion and prevent head cutting of channels along the valley. Approximately 25,000 feet of 15–24-inch diameter logs were placed across the entire valley at a horizontal spacing based upon 1.0-1.5-foot vertical elevation increase. The design approach is intended to provide valley grade control so the stream channel(s) that form can move across the valley and maintain the same channel invert elevation and if erosion occurs it is controlled and prevented from propagating beyond the next set of valley grade control logs. No bedrock controls are present throughout the site due to its historic mining. The surface of the floodplain was then covered in woody debris (treetops and logs) to provide habitat, roughness, and to assist in development of an anabranching channel pattern.
Restoration, Floodplain, Stream, Wetland
