Sediment Sorting During Coastal Restoration Projects: Implications for Resource Management, Environmental Impacts, and Multiple Use Conflicts

Beach nourishment projects using sand mined from offshore borrow sites must often meet sediment compatibility requirements including sediment size, sediment sorting, mineral content, sediment color, and fine sediment content. In many instances, the application of these regulations does not account for changes in these sediment characteristics from borrow areas to beach placement sites. Hopper dredging operations for beach and nearshore placement typically include periods of overflow at the borrow site and outwash at the beach, which changes the fine sediment content and color of sand ultimately placed on the beach compared to that of the borrow area. This study measured and compared sediment characteristics at the borrow area, in the dredge hopper, and on the beach to determine changes in sediment composition and characteristics associated with specific dredging operations. The study found that 87% of the fine sediment content of the borrow site sediments was removed in the process of dredging and beach placement. The dredging process reduced the fine sediment content and lightened the color of the sediment placed on the beach, two important factors for determining sediment compatibility with the native beach. This report recommends the application of simple, data-based estimates of fine-sediment removal to ensure compatibility of offshore sands with the receiving beaches.

USD: $400,000

2016-07-26 → 2019-02-15