Flash flooding and the flood hazard in Gatlinburg, Tennessee

The flash flood has in recent years become a very serious threat to those occupying the floodplains of the United States. The purpose of this study is to examine one such area which has a severe flash flood problem, in Gatlinburg, Tennessee, to delineate the hazard area, and evaluate the adequacy of a proposed flood warning system being implemented by the city and the Tennessee Valley Authority. Further, it is postulated that modifications of the floodway, such as bridges, buildings, and channel confinements can cause areas to be flooded that might otherwise escape inundation or suffer less damage.

The procedures for this study involved examining three historic floods and their characteristics to define the nature of the hazard in Gatlinburg, and the use of a series of floodplain topography maps to delineate the floodway. These characteristics include the floods' height, areal extent, velocity, and load. Characterizing the flood hazard in Gatlinburg provided the necessary information to delineate the floodway and identify the most hazardous areas in future floods. To be sure, no one can state specifically what may occur in a future flood, but systematic examination of these obstructions and encroachments in the floodway can identify which features will aggravate flooding and perhaps increase the dangers to life and property in Gatlinburg.

A description and evaluation of the flood warning system was then accomplished by examining the monitoring network, the nature and adequacy of the data upon which predictions of the severity of flooding are based, and the means for integrating the system with existing evacuation procedures.

It was found that flooding in the vicinity of Gatlinburg is extremely rapid in both onset and rate of flow. The proximity of the flood's source areas to Gatlinburg leaves little lead time to identify a potential flood and prepare for its approach. Modifications of the floodway in town effect the character of the flood locally and the patterns of scour and deposit through the town. These alterations make flooding in the town unpredictable and more hazardous. Under the present policy of verifying the flood's existence and magnitude before initiating the evacuation plan, and the circumstances of a severely constricted floodway through Gatlinburg, the warning lead time to effect an evacuation is too short to be effective, Moreover, the flood warning system is inadequate as a means of increasing the lead time preceding a flood, and considering the nature of the setting, no practical and fully effective warning system is possible. The planned integration of the warning system with the inadequate evacuation procedures for the town, and the lack of constraints on the use of the floodplain, are illustrative of the town's overall reluctance to recognize the hazard and its potential dangers. Further emphasis is needed in constraining development in the floodway through Gatlinburg to mitigate this environmental hazard. Short term measures, both in concept and implementation, are inadequate in view of the growth of the town and the tourist industry associated with it.