Lake Shoreline Restoration vs. River Shoreline Restoration
Whether your piece of shoreline is on a lake or a river, you want it kept secure and erosion-resistant, which means you probably want riprap installed. But how we create a durable riprap shoreline depends on whether you’re on a lake or on a river.
We’ve already talked about how to build a durable riprap shoreline on a lake.
Here are the factors you need to consider when fortifying your river shoreline:
1. Wakes. Most riverbanks get pounded with waves caused by passing boats. Because most rivers are much narrower than lakes, those wake-waves don’t have much room to flatten out before crashing into the shore and taking a little shoreline with them, with wave after wave.
2. Water levels. River levels almost always rise more than lakes do after a heavy rain or springtime snow-melt. (It’s like that narrow tall glass you sometimes get at a restaurant.) You should install riprap much higher up the riverbank to combat these high water levels. Remember: once water rises above your riprap and can get behind the fabric, your shoreline is wide open to a washout.
3. Current. The sheer power of the current means you need larger, heavier riprap stones, so that your riprap doesn’t get drafted into the Navy.
Also, because the current flows parallel to your shoreline, you need to take a couple of precautions. First, the aquatic filter-fabric installed on the upriver end of your shoreline shouldn’t have seams; they’d be exposed to the current, which would almost certainly weaken them and cause a blowout in your fabric. If a seam in the fabric is unavoidable, then it must be properly overlapped (i.e., shingled). Second, you may need to pile a little extra riprap on the upriver end of the fabric layer, so as to provide an additional layer of protection against current.
The location matters, too. If your shoreline is located on the outside bend in a river, you will have a much stronger current. That makes the precautions I described a minute ago even more important. Also, being on the outside bend in a river tends to wash out the underside of your shoreline. The riprap almost always needs to extend much further into the water than if your shoreline was on a lake, or even on the inside bend of a river. Outside-bend shorelines also require a thicker fabric to withstand potential pounding and stabbing from logs floating down the river.
4. Steep banks. Rivers almost always seem to have steeper shorelines than lakes. Rarely will you see an ideal 3:1 slope down to the water’s edge in a riverbank. It takes a keen eye to perfect the grade of riverbank. Too steep a grade and your riprap will slowly get washed out from the underside and get swallowed by the current. Too shallow a grade and you could lose a chunk of your riprap every year when the ice thaws.
5. Tree roots. Many rivers are lined with giant old-growth timber – like monstrous oaks and cottonwoods. Giant trees along a riverbank usually bring with them giant arrays of bare, washed-out roots along the riverbank. These roots need to be dealt with.
In most cases we can’t simply cover these exposed roots with fabric and riprap. Whenever possible, we like to cover the exposed roots with additional soil first. We then move in with fabric and riprap.
Often, though, we are left with no choice but to cut the exposed roots off entirely. (That typically doesn’t harm large, established trees.) Every situation is different, but regardless of what else happens we need to deal with the roots. Otherwise, they’ll interfere with your riprap and can compromise your entire shoreline.
As you’ve probably guessed by now, the Lakeshore Guys build durable shorelines on rivers as well as on lakes. Whether you choose our company or other shoreline restoration companies, make sure the riprap that is built on your river isn’t exactly like the one you’d build on a lakeshore.