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Currently, the Maine Department of Transportation and others design many culverts for streams that have drainage areas of less than one square mile. The accuracy of the flood-flow estimating methods for drainage basins of this size is poorly defined. There has been very little historical data collection in Maine on streams that have drainage areas of this size. A recent USGS study evaluated the accuracy of several flood-flow estimating methods for streams with drainage areas of greater than one square mile. The estimates from several methods were tested against gaging station estimates. Up to thirteen sites with drainage areas of less than 3 square miles were used in this test. From the limited sample of 13 sites, it is obvious that some commonly used estimation methods perform better than others. Better definition of the accuracy of these methods for Maine is needed to better design culverts. Better designed culverts will lower future damage from flood events and save substantial amounts of money.
The USGS, in cooperation with the Maine Department of Transportation, is conducting a study to provide the necessary information to objectively evaluate the accuracy of commonly used flood-flow estimating methods for streams with drainage areas of less than one square mile. USGS has install crest-stage gages and recording rainfall gages at about 15 streamflow sites with drainage areas of 0.2 to 1.0 square miles. These sites are located across the state and have diverse drainage-basin characteristics. The accuracy of several simple rainfall- runoff models will be tested for selected large runoff events at the gages.
Flooding at crest-stage gage on small stream near Cornish,
Maine