What is Natural Channel Stream Design?
Natural Channel Design (NCD) is a method of stream restoration accomplished by restoring the dimension, pattern, and/or profile of a degraded stream system by emulating natural, stable conditions. NCD was created as an environmentally sound alternative to traditional hard-armoring or channel straightening which does little to address the underlying cause of impairment to the stream and often times results in future channel degradation.
Sometimes NCD involves the installation of log or rock structures to achieve stability. For instance, bank erosion caused by high water events can be repaired or prevented by the installation of a structure to deflect the water, control the streambed grade, or slow velocities. NCD structures may also enhance fish habitat, facilitate sediment transport, establish grade control, and help the stream withstand large floods. Some structures may even enhance the stream visually and offer ease of access for public use.
Structures called j-hooks can help deflect the flow of water away from the bank and back into the middle of the channel, reducing bank erosion and providing habitat in the form of plunge pools for fish. Additionally, the rocks used in j-hook structures help to stabilize the bank and provide dwelling crevices for aquatic insects and other small animals. J-hooks are often accompanied by root wads which assist in bank stabilization, increase channel complexity, and create quality habitat for fish spawning, minnows, and aquatic insects.
J-hook on Dutch Creek in Valle Crucis, NC
Another common structure implemented in stream restoration projects are crossvanes, which direct flow and dissipate the stream’s energy in a plunge pool. By slowing down the flow of water, erosion is prevented and plants may even be able to take hold on the water’s edge. When applied in conjunction with other structures, crossvanes provide long-term stability while promoting floodplain connectivity, maintaining a stable stream for years to come.
Crossvane on Little Crabtree Creek in Micaville, NC
Natural Channel Design always includes riparian buffer planting with native plants and livestakes. Roots of the plants will secure the soil within the bank and prevent future erosion. Before planting, the banks are stabilized using plant fiber matting made of coconut or straw. Over time, the matting will biodegrade, and bank stability will be secured by the root systems of the vegetation. In addition to preventing erosion, a vegetated buffer can also filter contaminants from stormwater runoff including livestock waste, inorganic chemicals, and other pollutants that impair water quality. Exclusively using construction materials that occur in nature such as wood, rock, living plants, and plant fiber matting prevents man-made byproducts such as plastic netting and metal stakes from entering the stream, resulting in a healthier, more natural stream ecosystem.
There are countless other techniques used in NCD, and as the field continues to grow, more innovative designs are developed every day. BFEC is constantly engaged in the evolution of stream restoration and NCD, which is reflected in our carefully planned designs.