Physical Features
Topography and Geology
The topographic features of the Indian Lake Watershed were shaped by continental glaciation
and running water. The watershed is located in the till plains of Ohio's central lowlands.
The terrain is generally flat to gently rolling in the Van Horn and Blackhawk sub-watersheds
(0-6% slopes) with occasional steeper areas in the North Fork of the Great Miami River
sub-watershed (6-12 % slopes), and somewhat steeper terrain (greater than 12%) in the South
Fork of the Great Miami River. Much of the watershed consists of high lime glacial till of
Illinoisan and Wisconsin age (50 to 100 feet of thickness) overlying Devonian dolomite of the
lower Monroe formation. Because of the thickness of the glacial till, natural exposures
of the bedrock are few in number and small in size. These outcrops are frequently the sites
of quarrying operations. There are two active quarries in the watershed.
Soils
The soils in the watershed are derived mainly from high lime glacial till. The principal
type of soil in the watershed is silt loam with moderately slow subsoil permeability and a
slight to moderate erosion hazard. Eight major soil associations occur in the watershed.
The two most extensive associations, the Blount-Morley and the St. Clair-Nappannee (together
comprise 47 percent of the watershed area), have the highest slope and erosion potential in
the watershed. These soils are ranked as highly erodible, but are moderately productive for
row crop and small grain production. The soil characteristics in the watershed are conducive
to growing crops, which are important to the watershed's culture. Most soils in the
watershed are not well suited for septic system development due to low permeability, although
many areas of the surrounding counties are not well suited for development because of soil
conditions (wetlands, prime farmland, etc.). This generalization does not take into
consideration the site specific soil conditions.
Highly Erodible Land
The sloping terrain and loosely laid glacial till leaves the landscape prone to soil erosion.
The Natural Resource Conservation Service (NRCS) has a rating system for determining Highly
Erodible Land (HEL) using soil erodibility, rainfall and topographic factors. There are
currently 13,285 cropland acres of HEL designated land in the watershed. The watershed project
has been working to enroll HEL acres into Long Term Agreement (LTA) contracts in the CRP or
into a conservation tillage program. All of the HEL acres are covered under a compliance plan
developed by the landuser with USDA guidelines. Placing HEL acres into a conservation plan
allows implementation of practices which lower soil loss. Erosion is also reduced by taking
this land out of traditional crop production systems.
Wetlands
Wetlands have many functions, including storm water storage, wildlife habitat, and water
quality improvement. Wetlands are regulated by the U.S. Army Corps of Engineers, as outlined
in the Clean Water Act, Section 404. Wetland work requires a Section 401 water quality
certification permit which is obtained from Ohio EPA. Potential wetlands are identified by
referencing aerial photographs, soil surveys for the watershed, and the National Wetiand
Inventory (NWI) maps. Although an on-ground comprehensive survey of wetlands in the watershed
has not been conducted, the United States Geological Survey (USGS) has prepared draft NWI maps. These maps show numerous potential wetlands ranging in size from less than an acre to
40 acres or more. The most frequent locations of wetlands are along stream terraces,
although some potential wetlands may be found on the northern shore of Indian Lake. Wetiand
delineation is based on three parameters: soil type, vegetation and hydrology.
Forest
The number of acres of forested land, although remaining a significant land use, has declined
steadily since the 1987 National Resources Inventory estimates were made. Forest cover in
each of the tri-counties proportions of the watershed are the following: Auglaize - 1 %,
Hardin - 3%, Logan - 4%. The forest cover for the entire county are as follows: Auglaize - 5%,
Hardin - 7%, Logan - 13%. Most of the forest cover loss in the watershed has occurred mainly
because of the increasing number of acres in cultivation. However, some previously forested
land has been cleared for new residential development along the northern shore of Indian Lake.
More recently ODNR - Division of Forestry staff have observed an increase from 1990 through
1995 of forest land. The increase of tree and forest establishment in some areas of the
watershed is due to incentive programs implemented through the project.
|
