Monday, April 15, 2024
Adaptation & ResilienceEnvironment

Shrink a Yard, Grow a Beach: Housing on Feeder Bluffs

One day, a resident of Port Angeles, Washington could swing in a hammock in his backyard and look out over the Strait of Juan de Fuca to Victoria, British Columbia, and the undulating hills that surround it. A few days later, he couldn’t. The tree on which he hung his hammock had vanished, along with 40 feet of his backyard.

That resident’s house is on a bluff. Such houses and bluffs line much of the southern Strait of Juan de Fuca coast. I understand why people want to live in these houses. The instinct to feel on top of the world is strong. And what better way to feel that than to live on a cliff, overlooking sea and land that stretches to the horizon?

The Port Angeles bluffs and Salish Sea west of Ediz Hook
Feeling on Top of the World Comes at a Cost

Developing on bluffs has significant costs to the homeowners, the local geology, and the local community. Let’s start with the homeowners. Living on bluffs is risky because bluffs naturally erode, causing their edges to creep further and further inland. The Strait of Juan de Fuca bluffs recede up to 1.88 meters each year. And no one wants the tree on which they hang their hammock, let alone their house, falling off a cliff and into the sea.

The Port Angeles bluffs west of Ediz Hook. On the top right, a platform nears the edge

The costs to the local geology are more complex. Before we get into those, we have to understand how bluffs naturally work. Long ago, changes in relative sea level following the Cordilleran glacial retreat created the Strait of Juan de Fuca bluffs. Now, two main factors cause them to erode and move inland. First, waves erode the bases of the bluffs, which makes them steeper and steeper, until they collapse. Second, storms increase the water pressure in the bluffs, which decreases their stability and also causes them to collapse.

Together, erosion from waves and storms produces lots of sediment. This sediment feeds beaches and spits (strips of land that extend into the sea and are formed by sediment deposition)—thus the name “feeder bluffs.” The cycle of erosion and deposition constitutes two drift cells—one in Port Angeles from the Elwha bluffs to Ediz Hook and another in Sequim (the city that neighbors Port Angeles) from the Dungeness bluffs to the Dungeness Spit (the longest spit in the United States!).

Dramatic geology is a big sell for tourism and prospective housing development. While human intervention can slow erosion, it also interferes with natural processes. We shouldn’t be thinking about how to change nature, but rather how to change development.

People construct physical structures along the bases of bluffs—they “armor” them—to slow erosion and reduce the risk it poses. But slower erosion means less sediment for beaches and spits. Comparing Port Angeles and Sequim exemplifies this: 68% of the bluffs in Port Angeles are armored, compared to 1% of those in Sequim. As a result, the Port Angeles bluffs produce 55% less sediment, and Port Angeles beaches and spits are sediment starved. Following armoring, Port Angeles’ Ediz Hook received 89% less sediment.

This brings us to the costs to the local community. Simply put, beaches and spits are good for the community (including for the fish and juvenile salmon who need them to spawn and take refuge)! Sediment starved beaches and spits, however, are no good. And just like that, this turns into a classic story of a few (the homeowners) temporarily benefiting at the cost of many.

The Story Doesn’t Have to End There

There are two main areas that need action. First, to satiate the local geology and community, we should seriously consider removing the armoring from the Port Angeles feeder bluffs. Second, we should develop better estimates of the minimum distance between houses and bluffs based on the life expectancy of the houses and the rates of bluff erosion. If a home is expected to last 100 years, the minimum distance is an estimated 42 meters in Sequim and 40 meters in Port Angeles (with the present armoring). However, these estimates are from 2015, and finer-scale estimates would be a big improvement (i.e. at the scale of neighborhoods or houses rather than cities). If local regulations and state and local incentives included such estimates, we could significantly reduce the risk erosion poses to homeowners.

With time, the feeder bluffs will erode. Sediment will deposit on beaches and spits. The coastline will change. Rather than attempt to control that change, let’s anticipate it and control ourselves.

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