Flood-Plain Management.--The State of Michigan operates a flood-hazards program that is both service oriented and regulatory. Statewide services are provided by using hydrologic-engineering, water-resources, and community-planning expertise. Regulatory functions include a permit process and hydrologic-engineering review, inspection, and coordination activities. The flood-hazards program is administered by the Department of Natural Resources, Land and Water Management Division. The goal of this program is to minimize personal injury, loss of life, and property damage from flooding. The activities listed below are directly related to Federal, other State, and local agency programs. About 6 percent of the land area in the State is susceptible to flooding. For this reason, 650 communities or local units of government that have flood-prone areas have participated in the National Flood Insurance Program administered by the Federal Emergency Management Agency.
Individual elements of the program include the following:
(1) Regulation by flood-plain authority of the placement of encroachments such as bridges and culverts in riverine flood plains. The objective is to preserve the capacity to carry floodwater and to prevent obstruction to flows that increase flood hazards. Of the approximately 700 projects that are reviewed annually, about 60 percent are approved with conditions or modifications.
(2) Determination of flood risk by the subdivision review authority, using hydrologic analysis, for proposed housing subdivision developments.
(3) Provision of information by the flood-hazard information service that can be used at the design stage of a project to avoid flood-plain problems later. Information is provided for about 400 real-estate requests per year.
(4) Provision by the National Flood Insurance Community Assistance Program of technical assistance to communities in developing and administering flood-hazard regulations that are consistent with the requirements of the National Flood Insurance Program. About 650 flood-prone communities or local units of government participate in the program statewide.
(5) Flood-hazard mitigation of existing structures resulting from a program that recommends methods, materials, and techniques to decrease future flood damages. This service is available during disaster and nondisaster periods.
Flood-Warning Systems.--The NWS currently (1989) provides flood-forecast information at 74 locations in Michigan. This information is made available to radio and television stations, emergency service offices, and State police posts. A network of volunteer observers and 33 automated telemetering devices installed at strategic U.S. Geological Survey gaging stations provides river stage and rainfall data to aid in this effort. In addition, the Michigan Department of Natural Resources independently provides flood forecasts for a large part of the Grand River basin as part of a cooperative agreement with the NWS River Forecast Center in Minneapolis, Minn. As a result of major floods in 1985 and 1986 in southern Michigan, several communities have considered acquiring automated flood-warning systems, although none have been installed to date.
Water-Use Management During Droughts.--No State or regional water-conservation policies or drought contingency plans have been established in Michigan. Although water resources are generally abundant, Michigan occasionally is affected by droughts. The potential effect of consumptive water use on streamflow during a drought has been investigated in the River Raisin basin in southeastern Michigan (Fulcher and others, 1986). Inventories of all major water users were completed for the basin, and the natural low-flow characteristics of the river were estimated from streamflow records. By combining the inventories and low-flow characteristics, the effects of consumptive water use were calculated throughout the basin. The results indicate that consumptive water use substantially decreases the base flow throughout the river basin and, in fact, can dewater the river completely in some stream reaches. On the basis of the significant consumptive water losses in the River Raisin, an evaluation of other basins in the State to determine the effects of consumptive water use on natural streamflow would be beneficial.
