Ecosystem Viltality Drainage Basin Condition (DBC) Bank Modification (BM)
March 28, 2019 at 7:53 PMBank Modification measures lateral connectivity between the river or lake and its floodplain or riparian zone. It also provides a measure of the changes to instream processes and habitats likely to result from bank modification. However, directly measuring changes to connectivity, habitats and processes is difficult. Thus, as a proxy we measure the percentage of river channels (could also include lakeshores) affected by human modification, such as channelization or shoreline hardening.
Percent Channel affected by Modification (pCM)
| Attributes | |
|---|---|
| Scale of calculation: | Sub-basin; aggregate to single value per basin |
| Range of Output: | 100 indicates no modification and 0 highly is modified |
| Reference: | Nil |
| Type/Class of Input required: | (1) GIS layer of river network (2) Location of structures along the river including dykes, levees, channelization, etc. (3) Land use map |
| Suggested source of ‘minimum’ data to enable calculation: | (1) HydroSHEDS/HydroBASINS river network with manual correction at outflow (2) LandSAT imagery when appropriate (3) Aqua Monitor: http://aqua-monitor.appspot.com/ may be useful (4) Most recent Land use map |
Calculation in FHI Toolbox:
1. GIS processing
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Create a polygon based on buffer zone along streams and rivers. Default buffer size: 100m. If possible, allow user input.
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Intersect buffer polygon with land-cover data to generate table of land cover.
2. Classification (User-input)
For each land-cover type identified, assign weight based on following decision-matrix:
| Degree of naturalness | Management of water cycle | Pollution emissions | Vegetation characteristics | Examples | Weight |
|---|---|---|---|---|---|
| Natural and semi-natural | None | None | Native | Forest (primary and secondary); lakes (natural) and wetlands; native grasslands; native shrublands | 100 |
| Cultural assisted system | Low | Low | Mixed, high diversity | Mosaic native vegetation (>50%, vegetation cover <50%) | 70 |
| Low | Low | Mixed, moderate diversity | Mosaic cropland (>50%, natural vegetation <50%) | 60 | |
| Transformed system | Low | Low | Permanent cover with atypical species | Permanent pasture land; agroforestry; tree crops | 50 |
| Low to Moderate | Moderate to High | Seasonal cover with atypical species | Non-irrigated arable land | 40 | |
| High | Moderate to High | Seasonal cover with atypical species | Permanently irrigated arable land | 30 | |
| Completely artificial | High | Moderate to High | Sparse cover with grass | Urban park space; low-density suburban areas; barren land | 10 |
| High | High | None | Urban commercial areas; mining areas | 0 |
3. Aggregation
Scores within a sub-basin can be calculated as:
$$ CM = \left( \ \frac{\sum_{i = 1}^{m}{N_{i}\text{CM}_{i}}}{\text{TN}} \right)*100 $$
where, TN is the total number of raster cells in buffer polygon of m type, Ni is the number of cells of land cover type ith, and CMi is the appropriate score from the table directly above for that land-cover.