Going with the Flow
Culverts are a common feature of the built landscape; they allow water to pass under roads and trails, preventing erosion and flood damage. They come in all shapes, sizes, and materials. And when Northeast Wilderness Trust creates a new Preserve on former timberland, there is often a spiderweb of logging roads crisscrossing the landscape, with culverts sprinkled throughout. Such is the case on the West Branch Dead Stream parcel, a 2,300-acre section of the Alder Stream Wilderness Preserve in Central Maine. Culverts are not, however, a typical feature of a wild forest. This year, NWT received a generous grant from the USDA Natural Resources Conservation Service (NRCS) to remove these culverts and decommission the roads.
But wait a minute…if culverts allow water to flow, then what’s the big deal? Those familiar with our work may know that our approach is pretty hands-off. Once we create a Preserve, we like to let nature take its course from that point onward. Yet in the case of culverts, a little up-front restoration goes a long way in encouraging a healthy, connected watershed.
Take the example of a ‘perched culvert’, pictured below. There is a gap between the downstream spout of the culvert and the ground beneath it, creating a waterfall suspended in midair. Few if any aquatic creatures can jump this gap. The culvert essentially disconnects the upstream ecosystem from its downstream counterpart. What was once an integrated whole is now broken into fragmented pieces.
Culverts with smooth metal or plastic bottoms also break up the ecosystem, even if they aren’t “perched”. Many small critters (think invertebrates and fish fry) need natural stream beds littered with rocks and plants in order to move up and down the stream channel. In a smooth culvert, the water moves much too fast for them.
Finally, a culvert lowers the water table of the area surrounding it. Because the water is confined by the metal or plastic, it isn’t available to the plants that originally lived in that area. Instead of spreading out and soaking in, the water’s path is concentrated and narrow.
With all these details in mind, we decided to seek help removing the culverts at Alder Stream Wilderness Preserve, in the West Branch Dead Stream Parcel. NRCS awarded us a grant and we got to work! Our contractor removed 13 culverts and placed a few large boulders at the Preserve’s entrance to prevent motorized vehicles (below).
Before restoration work (below): This logging road cuts through the center of the Alder Stream Wilderness Preserve. Note that it is built up higher than the forest floor. In the foreground, a culvert runs beneath it (see the large boulders to the right).
After restoration work (below): The culvert has been removed and the stream channel re-established with rocks and boulders. The road has been regraded in this section to meet the forest floor organically, preventing the water from creating a deep channel or rut that would erode soil. Now, the water can properly disperse into the ground; fish and aquatic invertebrates can travel up and downstream; and the loosened soil will allow reforestation to begin more quickly.
Many thanks to our local contractor and to our generous funders!