Evaluating Natural Systems

In order to address land development within the context of environmental constraints and to encourage water resource enhancement, the Mitchell Creek Watershed Protection Strategy included an evaluation of the natural systems, including aquatic resources, wildlife, wetlands, geology and groundwater recharge and discharge areas.

Why were aquatic resources, wildlife, wetlands, geology and groundwater recharge areas included as an important natural system to evaluate?

Aquatic Resources

The study utilized a rating system to assess the biological condition of the streams. A stream habitat analysis included both a habitat and biological inventory, noting possible land use effects. The habitat and biological inventory was based on MDNR published techniques. Habitat features such as substrate type and depth, stream width and depth, overhead cover, undercut banks, riffle/pool formations, embeddedness, and macroinvertebrates were assessed at 25 locations. (Beckett and Raeder, 1995, p. 31) Whereas an earlier study in the watershed indicated that overall stream water quality was quite good and showed little signs of degradation, this study found some areas that were poor while others were found to be good to excellent.

What are the advantages/disadvantages of using historical data?

Wildlife






Critical wildlife habitats and corridors were identified using any one of the following criteria: an area of highest quality wildlife habitat which provides a diversity of plant species, food sources and protective cover; a habitat of at least 100 acres; or an area which serves as a wildlife travel corridor.

Wetland

Using site collected data and GIS analysis, wetlands were evaluated using a rating system of Critical, Important and Functional.

Critical Wetlands were designated if:

the area was at least 100 contiguous acres (easily determined using query functions in GIS),
the wetland area was adjacent to, or upstream of, streams rated as excellent cold water habitat (determined using stream data),
the wetland contained a plant community not common in Mitchell Creek Watershed,
or the wetland was contiguous to a critical wetland and adjacent to development which if expanded, could degrade the critical wetland.

Important Wetlands were determined by either:

adjacency to, or upstream of, streams rated as good cold water habitat (determined using stream data),
or by size between 5 and 100 acres (easily determined using query functions in GIS).

Functional Wetlands had at least one the following characteristics:

wetlands not rated as critical or important,
less than 5 acres,
and wetlands which were not contiguous to lakes, rivers, ponds or streams.

Groundwater Recharge

The Mitchell Creek Watershed Protection Strategy included an identification of potential recharge areas by evaluating near surface soils, topograpy and slope, depth to the water table, location in the watershed, land use, and water well logs. Michigan Resource Information Systems (MIRIS) land use data was used to identify land use types which were evaluated regarding their potential effect on infiltration of surface water in the watershed. GIS was used to input soil permeability, percentage clay between the ground surface and regional water table, and depth to the water table. Industrial, residential or commercial areas were not considered to be recharge areas since they have a large percentage of impervious surface. Other areas which had a high percentage of deeper subsurface clay were also not considered recharge areas. For each potential recharge area a slope range designation and a land use designation were assigned. Flatter areas with more desirable land uses were generally considered to be the best potential for recharge. (Beckett and Raeder, 1995, p. 81)