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Riparian Corridor Planning
Definition of Riparian Corridor For Mapping Purposes
Mapping Procedure
References
Presentation:  Riparian Corridor Mapping (493 kb)
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Definition of Riparian Corridor For Mapping Purposes
Many different riparian definitions are found in the literature (Welsh et. al , 19xx, Naiman et. al, 1997, Malanson, 1996). For community planning, a broad and consistent definition is required. The definition offered in the U.S. Fish and Wildlife Services A System for Mapping Riparian Areas in the Western United States was modified as follows:
Riparian areas are areas of the landscape that connect to and influence or are influenced by the surface and subsurface hydrologic features of perennial or intermittent waterbodies (rivers, streams, lakes, ponds, drainages, and wetlands).
Features of riparian areas include bottomlands containing the geomorphic floodplain, oxbows and abandoned channels, and uplands, containing valley walls, bluffs, terraces, and ravines.
Due to human development, encroachment, and management, riparian areas may contain altered features such as altered riparian areas, enclosed channels, and channelized (straightened) channels.
This definition is suitable for mapping and community planning because it clearly outlines the specific landscape features which comprise the riparian area. This specificity is useful to the GIS technician conducting the mapping to local governments formulating master plan policy statements, ordinance language, and design standards.
The individual physical features within riparian corridors of Oakland County are the result of the historical geologic activity that formed the river valley (Bay, 1938).
Uplands (Area above modern floodplain elevation):
Valley Wall: Sloped lands which enclose the river valley
Ravine: Steep sided- tributary channels which reflect rapid down-cutting such as during episodic lake-level lowering.
Terrace: Abandoned floodplains reflecting a former (higher) river base elevation during a historical lake stage.
Bluff: Valley walls with a steep slope (>10%) and a significant elevation change (20 feet or greater) with the floodplain or terrace below.
Lowlands (Areas at or below modern floodplain elevation):
Oxbow: Old channel that was abandoned as the river migrated that is still hydrologically connected with the modern river and may be inundated during wet seasons or flood events.
Abandoned Channel: Old channel within the floodplain that has been abandoned as the river has migrated and is hydrologically connected to the modern river only minimally or not at all.
Confluence Area: Area where two streams coalesce to flow as one; may include depositional deltas or delta-terraces.
Deltas: Depositional areas formed as ancient streams or rivers slowed in velocity as they formed confluences with other tributaries or flowed into glacial lakes or estuaries.
Lakes Area: Riparian area dominated by lakes and narrow inlet/outlet streams.
Marshy Area: Riparian area dominated by slow-flowing wetlands and marshes and narrow inlet/outlet streams.
Valley Floor: The modern river floodplain.
Modern Channel: The modern channel.
Altered Features (Any feature within the riparian corridor that has been significantly altered by human encroachment, development, or management):
Altered Riparian Area: Riparian area I which the topography has been so extensively altered that it is impossible to tell what underlying riparian physical features may exist.
Enclosed Channel: River channel that has been encased in metal or concrete and diverted through an underground path.
Channelized Channel: River channel that has been straightened to accommodate development or facilitate drainage.
Mapping Procedure
A clear and concise map of a riparian corridor system must be available in order to begin the planning process. Having a clear map allows communities to get a handle on the types of riparian resources they possess, what some of the ecological, cultural, and economic functional values might be, and what types of threats or conflicts might exist.
We have identified a basic approach for manually mapping the riparian corridors in Oakland County using Geographic Information Systems (GIS). This approach requires a highly detailed surface topography model derived from elevation data collected during the 2002 Oakland County aerial photography collection. The surface topography data was used to register the photography to Oakland Countys map projection system.
Using the topography model as a base layer, the following layers of information may be added as supplementary guidance:
* Surface hydrography
* Roads
* Recent and historical aerial photos
* Wetlands
* Flood Rate Insurance Map
* Soils
Using heads-up digitizing, the extent of the river valley and the features it contains are carefully delineated (Figure 1).
Figure 1: Delineated riparian corridor digitized using a detailed surface topography model
References
Bay, James William. 1938. Glacial History of the streams of southeastern Michigan. Cranbrook Institute of Science Bulletin No. 12
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