By Gordon Clanton
On a recent visit to the Torrey Pines State Beach, I came upon the sights and sounds of a major reshaping of the natural world. Two enormous bright yellow Komatsu excavators, as tall as
Tyrannosaurus rex,with articulated booms and tank-like treads, scoop sand from the mouth of Los Penasquitos Lagoon and from the tidal basin east of the bridge.
The wet sand is dropped into three huge bright yellow Caterpillar dump trucks, each with six wheels six feet in diameter. The trucks, belching diesel smoke, roar south along the beach, now cordoned off from public use. They dump the sand, some near the high tide line, some into the edge of the surf. A bright yellow bulldozer, beeping loudly when it backs up, rakes and smooths the new sand.
The sand replenishment is a side benefit. The main purpose of this activity is to re-open the lagoon mouth to the ocean. Although a new highway bridge built in 2005 greatly enhanced the tidal flow, the outlet still becomes clogged.
The health of the lagoon depends on the natural flushing action of the tides. When the lagoon mouth becomes silted in, the regular influx of seawater is blocked and the lagoon becomes stagnant and stinky. Mosquitoes breed here, then drift uphill.
Meanwhile the lagoon continues to be fed by fresh water, including the increased runoff from decades of paving and home construction in Del Mar Heights and Del Mar Terrace and the “urban drool” that trickles down from adjacent bluffs because of the continuous irrigation of a thousand bright green lawns.
As the lagoon fills with fresh water, the marsh becomes inhospitable to certain species of birds, fish, and plants that depend on tidal flushing.
As the water in the lagoon becomes less salty, a fresh-water mosquito (
Culex tarsalis) moves into the area — the mosquito known to carry the West Nile virus. WNV first appeared in the United States in 1999 and spread across the country from East to West. Infection can sometimes, although very rarely, be fatal for humans — one death in California (Sacramento) in 2013.
After mostly being open in recent years, the lagoon mouth closed in March. The slough was reopened in May but again became blocked with sand. The current activity is scheduled to last eight days and will cost the City of San Diego an estimated $100,000.
Gordon Clanton teaches sociology at San Diego State University.
He welcomes comments at firstname.lastname@example.org.