We understood there would be erosion when we purchased the property. It seems likely that clearing the land for the driveway and the house and clearing the yard for the view has hastened that erosion. We have a front row seat ticket for climate change and especially rising sea levels. I have been asked to be slightly mysterious about the actual location discussed here. I can tell you the property faces out onto the North Atlantic. The entire waterfront edge of the property is a cliff. The shoreline is 900 feet (300M) long. The cliff is about 50 feet high at the low end and rises to about 100 feet high at the other end. The cliff is a sandy bluff. Technically this is undifferentiated glacial till. It is mostly sand and clay with an average of 20% rounded river stones throughout. As far as I know, this property has been eroding since the last glaciation ended. I am guessing it has eroded ~ 1 km in 10,000 years, so 10cm of shoreline erosion on average per year. Our impression is that the average erosion rate is currently greater than that. My Karen and I are trying to push back. We know we can’t stop the erosion, but maybe we can slow it down.
Karen and I are pretty new to this place. We call the property, Storm House. It looks north-east over the ocean and allows us to stare straight down the gullet of the Nor’easters that blow through here from time to time. At the time of purchase, the property was entirely undeveloped woodland that had been clear cut 30 years earlier. There is now a young forest of birches and alders and spruce. The undergrowth provides a summer succession of strawberries, blueberries, raspberries, blackberries, and cranberries. By developing the property and just being on the land, we have changed things. Our vision as hobby homesteaders is to impose the smallest possible human footprint on an otherwise untouched natural environment. Government building codes, the policies surrounding bank mortgages and home insurance, and our desire for an ocean view make that a challenge.
Three ways that water causes erosion of the cliff:
- Wave action. During the biggest big storms the waves will wash up the beach and undercut the base of the cliff.
- Surface water going over the cliff. The soil has high clay content and is not very permeable. During the wettest storms the water will flow overland and over the cliff, creating runnels and trenches.
- A lot of water collects in the bog and sinks into the ground. The groundwater hits an impermeable layer and exits as spring water from the face of the cliff. The bigger the storm, the wetter the soil, the more likely we are to experience an erosion event.
This is a fanciful image of the property from the water. We were trying to imagine what a house (not to scale) might look like on the land. Of special note, you can see the impermeable layer above the beach where the groundwater springs forth. Curiously this is almost the same height as the undercutting erosion caused by the biggest waves. Note the patches of alders on the cliff. I am not sure if each patch is a single organism, but the roots of alders are so intertwined that thickets will stick together, even when they go over the cliff. We like these alders and are trying to propagate them. But they grow so slowly that new erosion may overtake them before they have properly taken root.
Erosion isn’t a continuous process here. It happens in discrete events. If enough water gets into the soil, the soil liquifies into a slurry and a section of the cliff will slump. It turns out that the rate of erosion is inversely related to the proportion of rocks in the soil. The rocks seem to hold it together. Ironically, the tallest part of the cliff — the part closest to the house — is almost rock free. For that reason, most of our erosion-control efforts are happening close to the house. Note the mud plume in the water. These happen all along the shoreline in this region and mud plumes from the biggest storms are probably visible from space.
We feel there are three key approaches to fighting erosion:
- Let nature do its thing. Plant growth soaks up water and provides a level of stability to the soil. The plants that are most likely to thrive will do so. Natural processes will establish some new dynamic equilibrium.
- Give nature a helping hand by repurposing weeds and low-value forest debris to seed the cliff. We are not sure how much our efforts improve upon the natural processes. But this is a way for us to feel like we are contributing.
- Create engineered solutions. These tend to be expensive, and the ROI is questionable. But in cases where the house is endangered, we may feel a need to intervene.
Slight diversion from the main story—but relevant. There is a new(ish) invasive-species weed in town. I think it is called Knotweed (the actual type of knotweed is the subject of some debate hereabouts). The plants produce extensive tuberous root systems. They seem to thrive anywhere there is no competition and do remarkably well in marginal soils like roadside gravel. Each new plant is connected to at least one of the others by a tuberous root. Their root systems collectively form a big network. The knotweeds have grown into a formidable patch at the end of our driveway where it meets the road. I have made it my personal mission to root out each-and-every knotweed in that patch and throw it/them over the cliff. I will be thrilled when they take root and form a massive patch facing the waves. Back to the main story.
A newly engineered solution (Karen’s idea) was to create a French Drain between the house and the cliff. The drain collects surface water and maybe some shallow groundwater along its length and steers it downhill. For us this is a diversion tactic that steers the water away from the house to a nearby hillside. And it works. We saw a steady flow of water from the end of the trench during the last big rainstorm. Eventually the water arrives back at the cliff again, but 100+ metres further away from the house. The aggregate you see here is from a gravel pit located on our road. We like to believe that it is environmentally ‘consistent’ with the local surface geology.
Karen and I are completely enchanted by this place and have been since we first laid eyes on it. We set the house 100 feet back from the cliff and, in those early days, we were somewhat dismissive of the erosion threat. We guessed we would be long dead before erosion got to the house. But maybe erosion will be the death of us instead. 😊 Time will tell. If you are still with us, thank you for your interest. We would love to hear your own stories and insights about managing the environment if you would care to share. Warmest regards to all.
~ Peter Ross, Karen Crouse, and Bentley the Wonder Dog.
