|
Natural Channel Design recognizes core geomorphic principles that occur on the landscape and shape stream channels. That natural process is key to achieving a stable channel that will develop and maintain the key attributes necessary to improve water quality and support biological communities.
Utilization of Natural Channel Design principles must be used as a guiding tool in restoration projects, but it must be kept in mind that streams ecosystems function at very different levels - hydraulically and biologically within various constraints or impacts such as urbanization or channelization. Understanding how these various components function as an ecosystem provides the foundation for the restoration process, which allows the stream to do much of the restoration work with natural trends and processes once a restoration site has been stabilized.
The very basis for NCD is the empirical relationships between the catchment area and the receiving channel. These are very broad relationships at a very large temporal scale. However, simply applying the shape of a great looking natural stream channel in an urban environment can spell disaster. Urban and modified watersheds require additional consideration at that scale and more importantly, attention to detail at the smallest temporal scale to provide a solid foundation for ecosystem recovery.
Stream ecosystems are much more than geomorphic relationships and the riparian area is more that a simplistic calculation of belt width, meander pattern and watershed size. The riparian area is an ecosystem unto itself, which supports the most diverse and dense flora and fauna populations in the landscape. The most common stream types, using the Rosgen Stream Classification, are very dependent upon a mature vegetated riparian zone to maintain a stable, and therefore functional, channel shape. Without that riparian vegetation, the channel shape itself will slowly self-destruct by means of entrenchment, braiding, or widening.
From an understanding of the watershed hydrology to the critical flows of a riffle, stream ecosystem restoration requires many important considerations across a broad temporal scale to provide a foundation for ecosystem recovery.
|
_top
