Saturday, November 30, 2013

Stone Steps

This is the first of two posts from this part of the Encinitas shoreline - the next one will be from Beacons, a short distance north. Stone Steps marks the dead end of South El Portal Street, just west of Neptune Ave, where an elegant public stairway leads to the beach.

This coastline is largely built on an old marine terrace, lifted above modern sea level by the chronic uplift of the California coast. The shore is cut into the seaward edge of the terrace, forming a steep 80' bluff that exposes layers of  sediment, mainly sandstone. Erosion patterns are cyclical, driven by climate and water levels and variations in the amount of sediment passing by on the beach.


Building along here encroached right to the bluff's edge (see the aerial view), perhaps during a period in the post-war era when erosion rates were low -- but most likely when opportunities in southern California land development were high. High water levels and storms during the 1983 El Nino hammered these bluffs, as have a number of subsequent events. There were numerous places where it was clear the bluff had slid in the past and many more where property owners had installed seawalls of some sort to counter the waves. Most were built almost flush with the steep bluff and many were camouflaged (this is afterall, the land of Disneyland and artificial landscapes) to blend with the tawny sandstone.  

The need to protect these bluff top homes may make perfect sense to the relatively small number of folks who live here, but it isn't sustainable in the long-term and in the meantime it represents a significant public subsidy. The naturalized seawalls may reduce the direct impacts on the beach, but they prevent the erosion of the bluff without addressing the erosion of the beach itself, so in the absence of other miracles the beach itself would eventually go away.

The miracle in this case is beach nourishment. In its absence, waves would increasingly pound the toes of these bluffs. In a future El Nino, there would be landslides and lost homes, emergency declarations, huge damage estimates, and sad stories of residents returning to condemned homes. Local communities would seek state and federal funds to manage the disaster. The coastline would be increasingly engineered (see next post). The public beach would be lost. The shoreline would begin to look more look like Pacifica.

In 2012, SANDAG completed the most recent round of nourishment. This is a huge public expenditure, and one with some adverse environmental impacts and much controversy.  It benefits the public by rebuilding and maintaining an accessible beach, but the only reason the nourishment is necessary is because of the need to protect these homes. If the bluffs could erode on their own, the beach would do just fine. The result is that private property benefits from a large public investment. I wonder if these folks see themselves as living in subsidized housing?

I'm a big fan of nourishment - in the right place and with adequate forethought to its geologic, ecologic, and economic implications. It's been a great boon to this coastline. But as the rate of sea level rise increases and the beach system gets farther out of equilibrium, the frequency and volume of nourishment will have to increase, along with its price.

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