Flash Flooding Across the Southern Appalachians: An Abbreviated Climatology with Forecasting Methods

and Techniques

Anthony D. Phillips, David A. Call, and Jill S. M. ColemanDepartment of Geography

Ball State University

Analyze the spatial and temporal extent of flash floods across the southern Appalachian Mountains

Create a hydroclimatology using credible reports Examine the influences of regional topography and

environmental characteristics (soil type, land use, etc) on the spatial distribution of flash floods

Gather information on the synoptic and mesoscale environments conducive to flash flooding across the region

Research Focus

Residents of the southern mountains are at greater risk due to:– Steep, complex terrain– Rapid accumulation of precipitation– Competition with mountain streams for roads, bridges,

housing, etc.– Mountaintop removal

The Flash Flood Threat

Previous hydroclimatological research has been limited to individual NWS WFOs (Gaffin and Hotz, 2000; Stonefield and Jackson, 2009).

Thorough, regional analysis will provide a better understanding of the extent of flash floods

Southern Appalachian Mountains:– Mountainous areas south of Mason-Dixon Line (~39.7° N)– Locations within the USGS Appalachian Highlands

physiographic division; namely the Appalachian Plateau, Valley and Ridge, and Blue Ridge provinces

Study Area: Southern Appalachians

Study Area: Southern Appalachians

Data obtained from the National Climatic Data Center– Storm Data from 1950 to 2010

Focuses on events after the Modernization and Restructuring (MAR) of the NWS in the mid-1990’s– Storm reports and verification– Abbreviated climatology: January 1, 1996 to December 31,

2010 Storm Data reports listed as either “flash flood” or

“flash flooding” Multiple events with similar/exact dates and locations

were consolidated into a single event

Data and Analysis

Results: Events per County

Results: Flash Flood Density

Results: Flash Flood Density

Results: Event Frequency

July 2007

July 2003

Frequency of events per year Noticeable variations, especially

between drought (’99, ‘07) and non-drought years (‘03)

Results: Event Frequency

Number of events that occurred during each month Frequency of events increases dramatically starting

in May– Substantial decrease in October

Results: Event Frequency

Results: Event Frequency

Events per time of day divided into 3-hr increments Number of events increases during afternoon/early

night hours

Results: Flood Severity Index

Results: Flash Floods per FSI

Results: Significant Flash Floods (FS3-FS5)

Results: Injuries and Fatalities

Results: Fatalities and Explanations

Future research will include examining the synoptic and mesoscale environments favorable for flash flood events across the southern Appalachians– Forecasting methods specific to the region

Additional spatial statistics such as average nearest neighbor and Geographically Weighted Regression– Geographically Weighted Regression (GWR) will examine

the relationships between prior flash flood events and other environmental characteristics across the region

Expansion of the study area to include the eastern United States

Upcoming Research

4,938 unique flash flood reports from 1996 to 2010 71 fatalities and 64 injuries As expected, greater number of events during warm season months

and during afternoon/overnight hours Higher fatality rates in regions with higher mean percent slope Future work will include:

– Additional statistical tests– Flash flood forecasting techniques

Results will assist meteorologists and hydrologists in forecasting flash flood events

For more information:Anthony Phillipshttp://www.wx4sno.comwx4sno@vt.edu

Summary