FLOODING IN HEADWATER STREAMS OF THE PIEDMONT: IMPLICATIONS FOR EMERGENCY MANAGEMENT

Understanding flood risk is important to emergency management agencies as they plan for extreme weather events. At the request of the Town of Davidson (North Carolina) Police and Fire Departments, we examined the flood risk at five locations deemed critical to emergency response efforts. In recent years, the Town of Davidson has experienced substantial shifts in land-use from agricultural and forested land towards suburban development. These changes increase the likelihood of flooding as impervious surface area increases. We used Mannings generated velocities, along with field and LiDAR derived cross-sections to estimate the discharge required to flood the five at-risk locations. We compared this data to historical data at a USGS stream gauge to estimate accuracy and determine approximate recurrence intervals. The drainage basins for the study sites consisted mainly of rural, forested, and suburban land-uses underlain by clay-rich soil. For one location, we found that the flood risk is very high, and the location floods multiple times a year. The flood risk was moderate at two locations, with the potential to flood every several years. For the last two locations, the flood risk was very low. This was true at Davidson Fire Station #2, indicating that the fire crews will not be hampered during high precipitation events. However, we found increasing trends of the yearly maximum flows and the mean annual discharge at the gauged location over the past 16 years. We interpret these results as an indication that on-going development may be increasing the risk of flooding in the Town of Davidson. We concluded that this stream system can produce considerable flash-floods and that this risk is increasing. That said, flood events under the current land use are unlikely to impact emergency response efforts.