Why our beaches are running out of sand
They’ll continue to shrink unless land use allows more sediment to flow downstream.
Do you enjoy a walk on the sand? Throwing down your beach towel and an umbrella to lose yourself for a few hours? Or a family barbecue with the kids building sandcastles? Enjoy it while you can.
Southern California’s sandy beaches are under duress and need our help. That became impossible to ignore this month, when the beach at San Clemente thinned so much that waves crashed over the rail tracks, making that line impassable. Service between Los Angeles and San Diego was suspended Sept. 16 and is expected to resume Monday after repairs. Beaches south of Dana Point, from Doheny through San Onofre, are especially at risk.
So far this isn’t primarily about climate change or rising sea levels. It’s about how local development and land use have altered natural processes that would have otherwise replenished the beaches.
Sand on beaches is a lot like money in a bank account. It flows in and out, and the balance needs to stay in positive territory to avoid a calamity of problems.
The sand deposits flow in from two natural processes: river inputs and cliff erosion. One human process contributes as well: beach nourishment, in which sand from one location is moved to another by machinery.
Sand flows out under the force of waves, creating rivers of sand along the coast that move material into sheltered areas such as coves, and eventually offshore into deep water. Once the sand is gone, our problems escalate: loss of access for millions of people and damage to property, infrastructure, fragile coastal wetlands and a $26.5-billion recreation and tourism economy.
So far with beach loss in Southern California, it’s not that our expenditures have increased but that our revenue is down. Development across the region has reduced the supply of sediment — in part through hardening of the land surface, which reduces the crucial erosion needed to create new sand, and in part through sediment capture systems used for flood control.
Climate change does come into play, though: Decades of drought have limited the number of big storms, which disproportionately account for the transport of sand to the coast.
Erosion impacts would have been felt sooner were it not for the widening of beaches across Southern California in the middle of the last century. The construction of ports, harbors and marinas in the 1930s, ’40s and ’50s dug out vast spoils from natural marshlands and sheltered areas, and the riches were placed along the coast. The construction of Dana Point Harbor in the 1960s and the San Onofre Nuclear Generating Station in the 1960s and ’70s contributed to beach widening from Doheny through San Onofre beaches — where beach sand is now vanishing.
Coping will be costly, with major undertakings such as rerouting critical infrastructure and maintaining public access to beaches.
Looking forward, climate change could make beach loss much, much worse, depending on how high we drive future sea levels with greenhouse gas emissions, global warming and polar ice melt. Curbing greenhouse gas emissions could still equate to several feet less of future sea level rise through 2100, and that would offer Californians many more days on the beach with family and friends and a far lower price tag for infrastructure adaptation.
Restoring sediment supplies will be crucial as well. Southern California has several options to do this:
▪ We can retool our flood channels and dams to deliver more sediment to the coast rather than capturing it upstream.
▪ We can ensure that armoring projects intended to prevent shoreline retreat account for diminished supply of sediment — and make sure those projects do not create barriers to public access.
▪ We can streamline permitting so local governments can more easily experiment and innovate with dredging and sediment placement, as well as using natural infrastructure such as vegetated dunes so beaches rise with sea level.
▪ The state and the region can more aggressively pursue federal funding for shoreline stabilization.
▪ We can collect data and build modeling systems that give us the understanding needed to manage these coastal systems better, avoiding the worst outcomes, sustaining our ecosystems and maximizing the delivery of benefits we’ve enjoyed for decades.
Just as no one event wiped out the beaches, no single solution will
renew them in a day. Long-term thinking is essential: The waves will keep washing away sand for as long as the wind blows over the oceans. If we help it, nature will carry sand to the beaches to replenish them.