With sea levels expected to rise 3 to 6 feet by the end of the century, coastal communities are moving fast to construct major shoreline projects to protect themselves. As the size of these projects expands, the primary building materials — dirt and mud — are getting scarce.
~ Lauren Sommer
Mud puddles, muddy feet, mud pies. The sensation of mud gooshing between your toes! Even in dry Texas, my childhood was filled with mud. We waded in creeks and ponds, and had to wash our feet off when we came out. The cross street at the end of our block was unpaved, offering the neighborhood kids a chance to build roadside dams when it rained. Our mothers were tolerant but insistent that we hose off before being allowed inside afterwards.
In Oklahoma, the red dirt permeated everything and swimming in the local reservoir resulted in permanent pink-tinged clothing. In the Arizona desert on the Navajo, walking across the muddy Colorado River floodplain would result in my boots collecting inches of mud — increasing my height and instability notably. I once worked with a survey crew there, and halfway across the floodplain their four-wheel drive vehicle dropped down to its hubs in the mud. I drove my pickup to within fifty yards and tried to pull them out with a winch, but it only sucked my truck deep into the mud. The several-mile walk in the hot sun to the nearest phone — at the trading post — reminded me to be more cautious in the future.
Mud, however, is more than mere annoyance or cherished childhood experience. Climate change is causing rising seas and it’s only going to get worse. We need to protect our shorelines, not just for human habitation, but for the salt marshes as well. These marshes buffer us from ocean surges and provide critical habitat for waterfowl and other creatures.
National Public Radio’s Lauren Sommer explains, “Dirt (what you dig up on land) and mud or sediment (the wetter variety already in rivers and bays) are the raw materials of climate change adaptation. They’re used to build levees, the massive earthen barriers that hold back waves, and to raise elevation so buildings can sit higher than the flood plain … Mud is also a crucial component of restoring wetlands and marshes, which act as natural barriers against storm surges while providing valuable habitat for sensitive species. In the right conditions, marshes can gain elevation over time from sediment, potentially keeping pace with sea level rise in a way that human-built infrastructure can’t.”
Our long-time favorite summer or fall vacation used to be at a seaside house on Cannon Beach, Oregon. It was situated at the top of a ten-foot reinforced dune wall about sixty feet away from the usual water’s edge. A few years ago, a rogue wave in a winter storm crested the wall and pushed a massive log through the plate glass windows into the living room. Climate change raises the sea level and increases storm frequency and surges.
Although that house’s location remains above normal wave height, much of the town is not. The risk to businesses and residents is real. A dozen or so years ago, early one morning, the town’s tsunami sirens suddenly wailed to warn of an imminent and potentially deadly wave caused by an off-shore earthquake. Grabbing our critical stuff, we drove to the nearest high point, where a crowd was gathered, facing out to sea. That tidal wave never occurred, but there were some pretty good parties at the evacuation spots.
As for most communities on the ocean’s edge, wave-proofing Cannon Beach would be incredibly expensive, probably massively disruptive, and likely ineffective. Natural barriers, like marshes, work the best if possible, but Sommer points out, “Centuries of human intervention have starved almost every major watershed in the country of sediment. Enormous dams, built to store water in rivers upstream, are essentially sediment entrapment device s… Nowhere is the problem more acute than on the Mississippi River, where dams reaching all the way to South Dakota are trapping sediment that once fed the wetlands of Louisiana.”
Looking for a spring in the mesas on the Navajo Reservation in the early ‘70’s, I walked up a canyon and found a stone dam, probably forty feet tall spanning the two canyon walls. I climbed up to the top, and found it dry, filled to the brim with sand. The dam had collected all the eroded soils from the watershed over the four decades since it was constructed as part of the Works Progress Administration projects of the 1930’s. Of course, now the sediment flowed freely over the lip of the dam. I considered at the time that that could be the fate of Lakes Powell and Mead on the Colorado River, as well, four decades hence.
Natural or artificial wetlands are not a solution to rising seas everywhere. Some beach communities or parts of them may be required to build massive structures or simply relocate to avoid the flooding. Regardless, the costs in terms of actual dollars and human impact will be enormous.
Sommers notes, “The long-term savings of avoiding flood damage from rising seas could dramatically outweigh the immediate cost of moving mud.”
So, maybe we need to get a little muddy, like we did when we were kids. Squoosh those toes!
Lauren Sommer, The Next Big Business in a Warming World? Mud, May 5, 2021, NPR