16 Sep 2024

Toward Systemic Beneficial use of Dredged Sediments in San Pablo Bay: Demonstration of a Proposed Framework for Matching Sediment Needs with Dredging Requirements

Abstract: Coastal wetlands provide a suite of valuable ecosystem services, but they are rapidly disappearing due to reductions in sediment supply and rising sea levels, making them ideal candidates for restoration through beneficial use of dredged sediment. Because sediment dredged from navigation channels is a limited resource relative to the number of degraded wetlands, a framework has been developed to align coastal restoration sediment needs with dredging requirements to maximize social, environmental, and flood risk reduction benefits while also completing the navigation mission. The framework is comprised of four key steps: (1) geographic scoping and suitability considerations, (2) quantification of the dredged sediment available and restoration project sediment needs, (3) definition of cost and benefit objectives, and (4) optimization of costs and benefits to determine the most efficient solutions. This report is a demonstration of this framework on a subset of wetland sites and local federal navigation channels in San Pablo Bay, California.

9 Jul 2020

PUBLICATION NOTICE: Hydrodynamics of a Recently Restored Coastal Wetland: Hamilton Wetlands, California

Abstract: Hamilton Wetlands is a recently restored tidally influenced basin located along the northwest coast of San Pablo Bay, California. Instruments to measure waves, currents, and wind were deployed for a period of up to 2 years shortly after tidal flow was re-introduced to the wetland to examine the sediment and hydrodynamic response. The results indicate that local re-suspension is relatively rare owing to the weak interior tidal currents and the limited fetch within the 3 km long basin. Asymmetries in the acoustic backscatter intensity combined with the much higher flow speeds measured at the entrance suggest a net import of fine sediment. The basin also experiences a distinct seasonal variation that likely contributes to sediment re-distribution. During the summer months, higher wind speeds correlate with turbidity suggesting local re-suspension of fines that are distributed by winds. Overall, the measurements suggest that the sediment dynamics in this shallow water system are controlled by two main factors: (1) net sediment import through the inlet entrance and (2) mixing of interior sediment through a combination of intermittent wind and wave stirring.