BENEFICIAL USES OF DEAD END CANAL DREDGING IN COMBINATION WITH SPECIAL USE MATERIALS FOR EROSION CONTROL

摘要

This paper looks at the obstacles that have to be overcome to improve or maintain the flushing of the canals and creeks. It will also give a practical example of an improvement project that helped with the channel flushing as well beneficial use of dredge material to help shoreline stabilization. The location of the project is off Assawoman Bay in Worcester County Maryland. In this case dredge spoils composed of organic silt from two dead end canals were used to develop a core for a shoreline stabilization project. The dredging was done in two natural canals (non-bulkheaded) with a total length of 1,000 meters and approximately 6,000 cubic meters. The project used a 0.4 meter dredge and took 4 months to complete.The primary reason for the project was to redevelop a navigable channel. Beside the practical use of the canal for docks and boating access, the project had two beneficial environmental effects. The organic sediment in the canals had accumulated over 40 years. The sediment was at least 0.7 meters thick and killed all sub-aquatic vegetation. This contributed to a high sediment oxygen demand that in turn developed dangerously low dissolved oxygen. Therefore, the first beneficial effect of the dredging was that it cleared out much of the organic silt and allowed for more efficient tidal flushing. This will eventually increase the bio-diversity of the water and sediment column in the canal.The second benefit was to use the sediment to naturally stabilize a highly erosive shoreline with a natural profile. Geobags were placed along the eroding shoreline and the sediment was pumped into the geobags. The geobags allowed for efficient dewatering and consolidation of the sediment. The geobags were covered with a permanent erosion reinforcement, articulated concrete block and a high performance three dimensional geotextile in a unique configuration.