Locust Beach on a sunny day. On the bluff, sediment and dirt are starting to give way. // Photo by Kenzie Mahoskey
Dirt crumbles from the touch of a hand at the bottom of the bluff near Locust Beach, raising concerns of erosion for community members.
Paul Thomas, senior geology instructor, said the bluffs northwest of Bellingham are so erodible because they’re composed of loose sediments that don’t have the internal cohesion and the strength of solid bedrock that lies under the soil.
The railway is right on the edge of the bluff, but it keeps on track with the erosion.
Burlington Northern Santa Fe Railway Company inspects the rails each week and measures erosion activity, Gus Melonas, BNSF Northwest public affairs director, said in an email.
The company has done some stabilization enhancement along the shoreline near Locust Beach. This location meets BNSF’s engineering safety guidelines, Melonas said.
Residents who live above the beach may be the cause of the erosion because they may not be handling their stormwater correctly, Andy Wiser, Whatcom County geologist and planner, said.
According to Whatcom County’s Stormwater Facilities website, houses near the edge have a high amount of stormwater because the rain runs right off their roofs and seeps into the cliff, causing erosion.
Locust Beach shows signs of erosion on the cliffs, and people who visit the beach can see it.
“If you go down the trail to Locust Beach and then turn left and walk a ways to the old concrete factory, you will see pipes sticking out of the ground,” junior geology major Austin Bolstad said.
Erosion near the houses could happen fast, or it could be over time that the house would physically start to sink, Wiser said.
“You’ll get a period of accelerated erosion or slope failure, maybe you could lose 5 to 10 feet of the cliff in one event,” Wiser said. “Then you could go 15 to 20 years without anything happening.”
Sometimes the erosion can happen every year at a slow pace like one inch annually, or it could be as much as 12 inches annually, Wiser said.
It also depends on how far the house is from the bluff. It’s not a great practice to build on unconsolidated sediments that are actively being eroded, Thomas said.
In order to reduce the erosion, residents of the area need to manage their property correctly, Wiser said.
“There’s various things you can do. It’s going to range from massive things like managing your stormwater [to] making sure it’s not saturating the edge of the bluff,” Wiser said.
There are other ways to reduce the erosion, too.
“Reducing erosion with vegetation can be a long process to occur naturally, so adding a geofabric on the slope to help the topsoil for the vegetation can help,” Wiser said. ”In some circumstances, people spend a lot of money putting tiles in, building a wall or regrading a slope to fix the configuration.”
Building on the bluffs makes for great views, but eventually the bluffs will retreat and reach the houses, Thomas said.