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LAND USE CHARACTERISTICS The majority of development in Iosco County is located along Lake Huron in the communities of Tawas City, East Tawas, Oscoda and AuSable. Urbanized areas take up approximately 1% of the County's land area. This development is centered around the County's lake shores. The majority of development in urbanized areas involves tourist and resort attractions. Approximately 64.3% of the County is forested. The majority of this land is held in trust by the state and federal governments, known as the AuSable State Forest and Huron National Forest, respectively. These holdings represent significant recreational resources for the County. Forests, inland waters, and wetlands comprise over 86% of the County's surface area. Agricultural uses account for approximately 10.7% of the area. All of the Townships and Cities in Iosco County have prepared individual Land Use and/or Zoning Ordinances. GEOLOGY AND TOPOGRAPHY In order to understand the geological and topographical features of Iosco County, one must first understand the geologic history of the State and also some of the geologic processes that brought about the various land forms. A brief over-view of the county will indicate a total relief of about 400 feet, with the high point being the 1,030 foot contour which crosses the extreme northwest corner of the county. From there, the terrain slopes towards Lake Huron, which is itself approximately 580 feet above sea level. Significant deviations from the gently rolling terrain can be seen in the "high banks" along the AuSable River and the moraine located roughly in the center of the County near the Silver Valley Winter Sports area. SUBSURFACE GEOLOGY Geologic time is measured in terms of "eras" which consists of many hundreds of million of years. In Michigan's lower Peninsula, the bed rock formations date from the Paleozoic and Mesozoic eras. During these last two time periods, this area had a climate quite different from that which we know today. For some time the area was covered by a warm tropical sea, then dense tropical swamp and finally, much later, by great glaciers. Sediments from the warm seas settled to the bottom and formed layers or strata of sedimentary rock. As the seas began to dry up and decrease in size, many strata were deposited in a layered pattern resembling a stack of saucers. The uppermost bedrock in Iosco County consists of materials from the upper and lower Mississippian series of the Paleozoic era. Various strata contain minerals of varied importance. In addition to the oil and natural gas which has formed in porous rock or pockets between strata, economic deposits of limestone, gypsum, salt & brine were found. In Iosco County, the Muramic-Osage formation of the Mississippian series is relatively close to the surface and considerable multitudes of gypsum are easily mined from it. It is interesting to note that gypsum is also mined in Grand Rapids from the same configuration. SURFACE GEOLOGY. Most of the topographic features of Iosco County are a result of erosion or deposition during the Wisconsin Glaciation, the last glacial period. The part of the glacier that covered Michigan began to recede about 14,000 years ago and moved completely out about 8,000 years ago. The glacial drift (deposit) that was left as the glaciers melted covered the entire County to a depth of several hundred feet. It formed such topographic features as moraines, till plains, outwash plains, lake plants and glacial drainways. The western edge of the county is covered by the Hale Till Plain. It is nearly level to gently rolling and is dominantly loamy and clayey soils. The dominate feature of the northern part of the County is the Jack Pines Delta. It is a sandy, nearly level to rolling area dominated by the Huron National Forest. The rest of the County is dominated by the Oscoda Lake Plain. This nearly level to undulating area is largely clayey soils with thin sandy caps in the southern part and sandy soils in the northern part. During the Pleistocene Epoch, the northern hemisphere was repeatedly invaded by glaciers. As many as four times the glaciers moved into the area and then slowly subsided. Each time they altered the landscape by gouging the surface and depositing large amounts of consolidated material along their margins. In Iosco County, two significant morainic formations can be seen; one in the area of the Silver Valley and the other in the northwest portion of the county. As the glaciers receded, melting water exerted a great influence on the terrain in Iosco County. Much of the area that encompasses the Huron National Forest is a large river delta. As the AuSable River passed through Alcona, Oscoda and Crawford Counties, it picked up sand and silt and later deposited them at the mouth of the river creating the delta. During this time, Lake Huron was relatively high and covered much of the eastern and southeastern portion of the county. The lake’s shoreline stretched from the west and south of Whittemore, northeast to Sand Lake, and on north through the delta area around Foote Dam. As the level of Lake Huron dropped, the river began to cut deeply into the delta thus creating the area known as the high banks. SHORELINE EROSION. Large bodies of water and wave action are responsible for yet another type of erosion. The lands adjacent to lakes, such as Lake Huron, are continually undergoing change due to erosion, or "littoral drift deposition." Sands washed away in one area are deposited elsewhere, in some instances treating new land forms. Tawas Point, for example, is a depositional structure composed of materials eroded by the AuSable River and delivered via prevailing currents and littoral drift patterns. Eventually, Tawas Point will extend to the opposite shoreline, with the Bay becoming a separate lake of its own. Lake Solitude, found within modern-day Tawas Point, was formed in this manner. Because shoreline erosion is a force of considerable significance and because shorelines are continually changing, caution should be used in considering development and construction along the lake shore. Caution was not observed along many sections of shoreline on the Great Lakes; consequently, the forces of wind and wave and the actions of man have caused a great deal of property loss. In an effort to attract attention to potential problems, the State of Michigan, through the Shoreline Protection and Management Act of 1970. The State has strongly recommended that communities adjacent to high risk erosion areas enact special zoning regulations or adopt other types of land use control which restrict development in these areas. SOILS. The composition and behavior of soils are extremely important to nearly every aspect of development. Stability, permeability, slope, depth, drainage, chemistry, fertility and wetness, among others, all bear on the suitability of land for particular uses. Knowledge of soils is elemental to environmentally sound growth. The soils in Iosco County run the gamut from slight to severe. They vary from deep, heavy clays to clay loams, sands and loams over clay, to deep, wet and dry sands, to shallow and deep mucks. The soil associations are slightly revised from the original soil classification used in Iosco County beginning in 1952. This was done to conform to the more efficient soil association nomenclature used virtually everywhere in the state. A modem soil survey has been completed and was released on March 14, 2003. The Soil Survey of Iosco County can be secured from the Iosco Conservation District in Tawas City. A CD-Rom version of the survey is also available. WATER RESOURCES. Adequate supplies of both surface and ground water is one of the most important elements in shaping the land use patterns in Iosco County. Their importance to recreation, residences, agriculture, wildlife, commerce and industry cannot be overemphasized. The continuing need for adequate amounts of good quality water is of prime importance to future growth. Existing sources of potable water must be protected to supply the needs and ensure the health of a growing population. The County has about 12,000 acres of scattered lakes and ponds. These water areas range from less than 5 acres to more than 1900 acres. Some lakes are located in marshes and exhibit all stages of filling by vegetation. Most of the lakes are in the northern half of the County. Among the larger ones are Cooke Pond, 1942 acres; Foote Pond, 1824 acres; Tawas Lake, 1670 acres; Van Etten Lake, 1320 acres; Long Lake, 493 acres; Loon Lake, 417 acres; and Sand Lake, 240 acres. Iosco County has three major drainage systems - The AuSable River, the AuGres River and the East Branch of the AuGres River. CLIMATE. Climate, the average weather conditions occurring in a particular area over time, has a direct bearing on nearly every feature of the natural and cultural environment. For this reason, climate must be considered in any discussion of natural processes. Iosco County, like most of the lower peninsula, is affected by prevailing westerly winds which are modified as to temperature and moisture content as they pass over Lake Michigan. During the winter, cloud cover produced by this "lake effect" prevents the loss of long wave radiation to space and thereby maintains somewhat warmer temperatures for Michigan than would otherwise occur at this latitude. Conversely, winds moving over waters of the Lakes during the summer keep Michigan comparatively cool. Average temperatures over a thirty year period of record are not significantly different between the two stations in the County. The mean temperature for the hottest month, July, is 69.9°F at Loud Dam and at East Tawas it is 68.0°F. February, the coldest month, records a mean temperature of 17.2F° at Loud Dam and 18.8°F in East Tawas. Average temperatures are generally warmer along the Lake Huron shoreline than in the interior for two reasons: 1) forest cover provides insulation during the summer inland, and 2) the lake serves as a heat source in the winter along the shore. Precipitation in Iosco County averages 28.78 inches per year. Precipitation is heaviest during the growing season (April-September) providing 61 % of the annual total at the Loud Dam station and 65% at East Tawas. Total average precipitation is highest in August at Loud Dam, averaging 3.38". In East Tawas, August has the heaviest total rainfall averaging 4.74". March is the driest month averaging 0.40" at Loud Dam and 1.08" in East Tawas. Snowfall averages 50.2" annually at Loud Dam, with wide variations from winter to winter. In East Tawas, snowfall averages 51.3" a year. The difference in snowfall, between the two stations indicates that Lake Huron's proximity is a potential source of lake effect snowfall. WIND. Wind direction and speed significantly influence the extent to which Lake Huron modifies the weather in Iosco County. Prevailing winds in the area are from the northwest during all but the months of May and June, when southeasterly winds predominate. Lake breezes are also common during daylight hours in July and August as air heated over sunwarmed land rises and is replaced by cooler air masses from Lake Huron. Mean annual wind speed is 7.3 mph with the greatest average velocities occurring in April (8.6 mph) and the least in August (6.1 mph). |
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