Coastal Armoring and Erosion
About 85% of the California coast experiences active erosion due to natural and anthropogenic causes. Storm damage continually erodes away at the coastline, most notably during El Niño years such as the 1982–1983 episode, and even more recently in the winter of 2023. This ongoing erosion, which is largely a natural occurrence, presents a threat to coastal development that has occurred in areas vulnerable to these processes. Hard surfaces, such as concrete, cover large portions of land, impede the natural absorption of water, and thus exacerbate surficial erosion on adjacent unprotected land. In some areas, natural sand transport to the coast has declined due to the damming of streams and rivers. Increases in coastal development also have led to storm-related damage.
Sanctuary regulations prohibit alteration of the seabed, and all armoring structures placed below the mean high tide line require approval from Monterey Bay National Marine Sanctuary. The sanctuary regulates coastal armoring by authorizing California Coastal Commission permits, and issuing specific conditions on those permits.
Throughout its first decade since designation, Monterey Bay National Marine Sanctuary's review of seawalls primarily focused on minimizing impacts from the construction process rather than long-term impacts from the armoring itself. In 2002, as part of the management plan update process, sanctuary staff shifted focus to conducting long-term planning as to the consequences of coastal armoring and its effect on some of the sanctuary's most sensitive resources, including beaches, bluffs, and coastline. A Coastal Sediment Management Working Group was formed with the goal of developing a proactive regional plan for the northern and southern Monterey Bay shorelines. The plans include identification and assessment of potential site-specific and sub-regional alternatives for addressing coastal erosion and recommendations as to when and where specific alternatives should be used. Monterey Bay National Marine Sanctuary worked with the U.S. Army Corp of Engineers and interested stakeholders to develop the Coastal Regional Sediment Management Plans for the Santa Cruz and Southern Monterey Bay Littoral Cells.
The 2021 Monterey Bay National Marine Sanctuary Management Plan regulations were updated to allow for the beneficial use of harbor dredge material for beach nourishment. NOAA added a new definition for “beneficial use of dredged material” to Monterey Bay National Marine Sanctuary regulations and clarified NOAA’s ability to authorize beneficial use of suitable dredged material for habitat protection and restoration purposes within the sanctuary. This regulatory change was conducted so that suitable harbor dredge material from the four local harbors can be used for habitat protection and restoration projects. In this area, placing sediment on an eroding beach can help protect it from further erosion, and the sediment can contribute to the coastal sediment transport system, which provides sediment to other nearby coastal beaches. Nourishing beaches also helps protect coastal dunes, which provide habitat for threatened and endangered species, such as western snowy plovers. NOAA also recognizes that there may be ancillary benefits from these projects, such as the protection of coastal infrastructures, including the use of softscape erosion control alternatives, shoreline stabilization, and adaptive management to address sea level rise.