Engineered flood protection such as levees or floodwalls are designed to protect inland areas from a 100-year water level. Engineered shoreline protection includes revetments and bulkheads that help to reduce erosion. Non-engineered berms separate managed marshes and ponds from the Bay and can also provide “ad hoc” flood protection.
These structural shorelines assets are owned, maintained, regulated and financed by a complex system of local, regional, state and federal agencies, including the Hayward Area Recreation and Park District, East Bay Regional Parks District, Port of Oakland, Alameda County Flood Control and Water Conservation District, California Department of Fish and Wildlife, and the US Army Corps of Engineers.
Structural shorelines are vulnerable to sea level rise and storm events that expose them to additional tidal currents, wave energy, runup and overtopping, which can weaken them and increase the potential for failure and flooding. Engineered flood protection is vulnerable to levee crest and backside erosion if overtopped, while engineered shoreline protection is vulnerable to mobilization of the armor layer and erosion of the foundation. Non-engineered berms are especially vulnerable to erosive wave and tidal action because they have not been designed or constructed to withstand these forces and are often not maintained on a regular basis.
The vulnerability of any particular stretch of structural shoreline in the project area depends on its location, type, design and maintenance. Structures with space to be expanded or improved, that have dedicated funding and permit authorizations for maintenance and improvements, and are already included in long-range capital improvement planning are more likely to be in or have capacity to be improved to a better structural condition, and are therefore less vulnerable. Realignment of some structures to a new inland position may be necessary in some instances, and a multi-agency approach will be required to assess the feasibility and potential effectiveness of these types of projects. Planning, financing, and coordinating the ongoing maintenance or capital improvements of structural shorelines is complex as they are often owned by one entity and maintained by another, and are regulated by a number of different agencies.
The consequences of damage or failure of structural shorelines depend on the assets they protect, but will most likely result in the loss of critical facilities, services and infrastructure that local communities, the region, and in some cases the state and nation, rely upon. One of the most significant challenges with structural shorelines and the assets that they protect is that the owners of those assets do not own and are not responsible for the protection. In many cases, asset owners do not know that their properties are protected by structural shorelines. Even if they are aware, they do not know who owns the structures that are protecting their property.
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- Lindy Lowe