Compatibility Analysis of Dredged Sediments from Routine Pathways and Maintenance of Harbor's Channels for Reuse in Nearshore Nourishment in the Nile Delta, Egypt

摘要

Dredged seabed sediments from Nile Delta pathways and maintenance of harbor channels were analyzed for compatibility with samples from five eroding beaches as potential borrow material for nearshore nourishment. Dredging sites were essentially centered at Abu Qir bay, Rosetta estuary, Burullus harbor, the Damietta approach channel, and El Gamil inlet near Port Said. Compatibility analysis of core and seabed samples collected from the dredging areas with the native eroding beaches was performed using multiple methods, including graphical comparison of grain size distributions (scatter plots, cumulative curves, and frequency curves), overfill (RA), and renourishment (R-J) factor models, the "half-life time" of the specified beach fills, and the volume of borrow sediment required to maintain equilibrium in the beach/littoral system. Results indicate that the compatibility of the dredged borrow sediments to the native material varies locally from fairly compatible (Rosetta estuary, Burullus harbor, Damietta approach channel, and El Gamil inlet) to incompatible (Abu Qir bay). Because of the wide range of grain-size distribution of dredged sediment, only 18-51% of the sand fractions evaluated were compatible with native beaches. However, excessive volumes of dredged sediment can compensate for dredging sites with low proportions of sand, estimated between 2.5 and 4.7 times the volume required using compatible materials to maintain the equilibrium profile. Furthermore, the frequency of nourishment operations would be 0.33 to 3.0 times more often than would be required with a fully compatible borrow material. For economic, environmental, and technical considerations, engineering procedures for nearshore nourishment (underwater nourishment) are recommended as an appropriate mitigation to eroding coastlines in the Nile Delta.