Riparian Restoration: Lessons Learned so far

One year in, I thought it advisable to reflect on the process of and progress (if any) toward the restoration of the woodland area on both sides of the stream running through our lot.

We are responsible for a stretch of both banks of Gilbert Creek, an “urban stream” whose history remains obscure to me. Based on a series of disjointed internet searches and conversations with townspeople, the stream may (or may not) have once been called “Skunk Creek,” may/not have once have been brimming with salmon, may/not now be kept flowing these days through artificial means as a irrigation canal.

Lore aside, the creek suffers from several challenges that afflict “urban streams” generally. These include: flooding and pollution from runoff of impermeable surfaces such as streets, sidewalks, parking lots; associated erosion; unpermitted efforts to manage erosion via building walls; and displacement of natives by invasive species.

Our efforts were initiated in response to frustration with the dominance of nonnative ivy, vinca, Himalayan balckberry, and Japanese knotweed on our banks. I leave bamboo off the list not because it’s native and not because it’s non-invasive, but because it pretty much holds the bank together and – let’s face it – it’s not going anywhere. Added to which, we get a lot of use from the bamboo poles and we kinda like it.

We learned to respect the roles that these nonnatives were playing in providing groundcover and preventing erosion. Once the vinca and ivy were torn out, the ground was left pretty bare, exposed to the winter rains. While native species were getting established, it was necessary to cover the ground. Several methods were tried: leaf mulch was spread on flatter areas. Heavy branches were placed on slopes before they, too, were mulched. On one particularly precipitous slope, we resorted to burlap fixed in place with landscape staples. Of these methods, the burlap was the least effective, as it quickly sagged, leaving bare patches.

So far, maintenance of the areas where nonnative species have been removed has proven quite manageable. The inevitable ivy or vinca emerging from roots left in the soil is gently removed, a task required maybe every 3 months. The knotwood is a different story altogether. The current plan is to keep cutting it down, both to weaken the plants and to ensure that they do not shade out the natives planted around them.

Introducing natives has proven more complicated than expected. I have learned the hard way that not all “Oregon natives” are suited to the drier climate and hot summers of the Rogue River Valley, particularly in the context of climate change. A year on, I am eagerly looking for signs of growth to determine which species have fared the best in our particular conditions. I have also come to respect that irrigation during the first year after planting is nonnegotiable. I have suffered preventable losses due to inadequate watering and will not make that mistake again. Once established, the natives should be low maintenance.

The bank closest to the water’s edge has presented its own challenges. Some areas are sandy, some rocky, some cut away. In the sandy and even the rocky areas, it has been possible to plant plugs of red twig dogwood, Douglas spirea, and willow. Stakes and lateral branches are used to secure the plants in case of rising waters while they are becoming established. The undercut areas lack growing medium at the water’s edge, while bamboo roots make planting in the bank above prohibitive. In these areas, willow stakes will be driven deeply into the stream bed itself. In time, these should capture detritis that will decompose into a medium where other plants can grow.

Thanks to our neighbor K who has been so instrumental in our restoration work.

7 thoughts on “Riparian Restoration: Lessons Learned so far

  1. Interesting. Having a stream must be both a privilege and a challenge. Thanks for describing your restoration efforts.
    Himalayan blackberry and ivy are terrible invasives everywhere in the Pacific Northwest. I have two kinds of vinca (major and minor) and subject them to harsh treatment and occasional thinning out. That has kept them from carpeting everything.

    Liked by 1 person

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