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Sands of Time
Dwight Worden | Seaview Avenue

After extended community discussion and debate, Del Mar adopted a Sea Level Rise Adaptation Plan that relies on sand replenishment, river dredging, and if needed, a living levee along the river to reduce flooding risk—not just to beach front properties, but to the low lying properties between the beach and the railroad line as well. That Plan is pending at the Coastal Commission, expected to be reviewed this fall. Let’s look at the sand replenishment portion of this strategy.
A wide sandy beach is not only essential if Del Mar is to maintain its great recreational beach and tourist-based economy in the face of rising sea levels, but is also the best way to protect homes and public infrastructure (street ends, Powerhouse Park, sewer lines, etc.) as we face sea level rise. This is why sand replenishment is a key aspect of our city’s Adaptation Plan.

How much sand do we need? SANDAG, Scripps, and others have been tracking our beach width since at least the late 1990s. A 2009 analysis made some early predictions, and part of Del Mar’s efforts is a more recent sediment study. From this information, given our best estimates of likely sea level rise, and assuming periodic major storms that wipe out the beach, a rough estimate can be made of how much sand we will need to keep even with sea level rise.

Where will we get it? The considerable amount of sand in the San Dieguito River back to the Jimmy Durante Bridge could be one source of sand for our beach. While SCE periodically dredges the river mouth to keep it open as required by its Coastal Permit for the lagoon restoration, SCE does not dredge farther up the river. With the right permits and some funds, Del Mar can join with future SCE dredging projects to move more sand from the river to the beach. This will build our beach and increase the capacity of the river to carry flood waters.

Another source is “opportunistic” sand—sand from construction projects and the like. A key City Council priority is obtaining a SCOUP permit (Sand Compatibility and Opportunistic Use Program) so we can acquire this sand as available. Our SCOUP permit must be approved by the resource agencies (Fish and Wildlife, etc.) and the Coastal Commission.

A factor to keep in mind, however, is that the whole sand system is complex and dynamic covering the littoral cell between Dana Point and La Jolla.

The upside of this dynamic system: we benefit from sand placed on the beaches of Solana Beach, Encinitas and points north as it travels south. The downside: we lose sand that travels south. Some of this travelling sand gets trapped in the mouth of the San Dieguito and Los Penasquitos Lagoons, requiring dredging and maintenance. Some sand gets pulled offshore, and sand is eventually lost to the off shore La Jolla trench to the south of us.

Depositing sand just on the Del Mar beach is not likely to work well since it is likely to be carried away unless our neighbors are engaged in the process with us. SANDAG has already undertaken two regional beach sand replenishment projects (2001, 2012) and, with Del Mar’s support, is beginning work on a third regional program. For Del Mar the way to go is participation in these Regional Beach Sand Replenishment projects.

How much will it cost? The cost of a successful regional program is in the millions, with Del Mar paying its fair share. With SANDAG in the lead we would look for federal and state grant funds. Grant requests that include local matching funds show “skin in the game” and compete better than those that ask for 100% funding.

Our best approach is to get our SCOUP permit, pick up sand where and when we can, and work with SANDAG to implement regional sand replenishment projects.
To learn more about this complex subject visit the City’s webpage on Sea Level Rise: https://www.delmar.ca.us/498/Sea-Level-Rise-Local-Coastal-Program-Ame


 

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