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Research about Decatur, Indiana

Source-linked reports with geographic coverage including Decatur, Indiana.

2 recordsLinked to original sources
USGS2015

Flood-inundation maps for the St. Marys River at Decatur, Indiana

Digital flood-inundation maps for an 8.9-mile reach of the St. Marys River at Decatur, Indiana, were developed by the U.S. Geological Survey (USGS), in cooperation with the Indiana Office of Community and Rural Affairs. The inundation maps, which can be accessed through the USGS Flood Inundation Mapping Science Web site ( http://water.usgs.gov/osw/flood_inundation/ ), depict estimates of the areal extent and depth of flooding corresponding to selected water levels (stages) of the St. Marys River at Decatur (USGS station number 04181500). The maps are useful for estimating near-real-time areas of inundation by referencing concurrent USGS streamgage information at http://waterdata.usgs.gov/ . In addition, the streamgage information was provided to the National Weather Service (NWS) for incorporation into their Advanced Hydrologic Prediction Service flood warning system ( http:/water.weather.gov/ahps/ ). NWS-forecasted peak-stage information may be used in conjunction with the maps developed during this study to show predicted areas of flood inundation. During this study, flood profiles were computed for the stream reach by means of a one-dimensional, step-backwater model. The model was calibrated by using the stage-discharge relation for the streamgage at St. Marys River at Decatur. The hydraulic model was used to compute 18 water-surface profiles for flood stages varied at 1-foot (ft) intervals and ranging from approximately bankfull (13 ft above gage datum) to greater than the highest recorded water level at the streamgage. To delineate the area of flood inundation for each modeled water level, maps were constructed in a geographic information system by combining the simulated water-surface profiles with a digital-elevation model derived from light detection and ranging (lidar) data. Estimated flood-inundation boundaries along each simulated profile were developed using HEC–GeoRAS software. The availability of these maps and associated Web mapping tools, along with the current river stage from USGS streamgages and forecasted flood stages from the NWS, provides emergency managers and residents with information that may be critical for flood-emergency planning and flood response activities such as evacuations and road closures, as well as for post-flood recovery efforts.

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USGS1983

Lineaments and fracture traces, Decatur County, Indiana

Lineanents and fracture traces have been mapped throughout Decatur County, Indiana. These lineaments and fracture traces may indicate that solution enlarged vertical fractures in the limestone and dolonite aquifers underlie most of the county. The use of lineament and fracture-trace maps in selecting bedrock-drilling sites results in a significant increase in the number of usable sites. Bedrock wells drilled on or near mapped lineaments and fracture traces have a higher average yield than veils drilled into interfracture areas. Parts of Decatur County and several adjacent counties are economically restricted by inadequate water supplies. The Greensburg Municipal Water Works, supplying 35 percent of the county's population, obtains 25 percent of its water from six wells in Greensburg. The remaining 75 percent is pumped from the Flat Rock River. This water is piped 8.25 miles and lifted 183 feet to the treatment station. Although the Flatrock River has adequate flow to supply Greensburg's water needs, a ground-water supply can probably be developed nearer the treatment plant. Pleistocene till covers most of the nearly horizontal bedrock. Although averaging about 50 feet thick, this unconsolidated unit does not seem to inhibit the mapping of lineaments and fracture traces. Bedrock is middle Paleozoic limestone, dolomite, and shale. Two sequences of limestone and dolomite, separated by a thin shale unit, constitute the principal aquifer. The extremely variable well yields from this aquifer indicate that the bedrock permeability is also variable. Well placement is important in a fractured bedrock terrane, as fractures are a principal source of water to the well. Here, the most productive bedrock wells are at the mapped intersection of two or more fracture traces or lineaments and at the lowest local altitude. Use of a fracture-trace map will not guarantee a sufficient supply of ground water but will reduce the chance of drilling an inadequate well.

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