Flood Plain and Alluvial Soil Maps

 

Because of the dam's presence, flood risk management at Carvins Cove differs from that of the Roanoke River. While nearby streams may experience flash floods during heavy rain, the primary flood concern for the Carvins Cove Reservoir area is the rare possibility of a dam failure. The Carvins Cove flood plain refers to the downstream area along Carvins Creek that is at risk of flooding during extreme weather or in the unlikely event of a dam breach. 

Key facts about the Carvins Cove flood plain: 

• Downstream flood path: Excess water from the reservoir flows over the dam's spillway and into Carvins Creek, which can cause flooding downstream during periods of heavy rain. 

• Flood events: Major flood events have caused the dam's spillway to overflow, notably in 1985 and twice in May and June of 2020 due to heavy rainfall. 

• Dam safety and emergency action levels: The Carvins Cove Dam is designed to withstand significant overflow and has an emergency action plan. 

• A Stage II notification is issued when two feet of water flows over the spillway, which is not an indicator of imminent failure but prompts notification of emergency personnel. 

• A Stage III emergency, signaling an imminent failure, would be triggered if four feet of water flowed over the dam. A 2014 study determined the dam would not fail until 14 feet of water overtopped it. 

• Official risk information: The Western Virginia Water Authority provides information about the dam's status and inundation zones in the case of a breach. 

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• References

  Reservoir dams | Western Virginia Water Authority. (n.d.-k). https://www.westernvawater.org/water/reservoir-dams

  Dam Safety Support Annex II. concept of operations. (2007, September). https://www.roanokeva.gov/DocumentCenter/View/535/Dam-Safety-PDF

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I created several maps showing the flood plain.

this one is from: https://gisweb.roanokecountyva.gov/floodview/#:~:text=Floodplain%20Inquiry,data%20in%20an%20appropriate%20manner.

Here is the one from ArcGIS

This one is from FEMA

 

Here is another from  USDA

It showed that the Berks-Weikert complex soils of Carvins Cove area of Botetourt County, Virginia occur on hilly uplands at elevations of 300-1,600 feet, with 15-60 percent slopes, moderate precipitation (30-45 inches annually), and cool, temperate conditions. Berk soils are well-drained, moderately deep, and very rocky, while Weikert soils are even shallower and somewhat excessively drained, both have very low available water capacity and are underlaid by shale or siltstone bedrock within 10-40 inches. These soils, along with associated units such as Gilpin silt loam and Laidig cobbly fine sandy loam, are not considered prime farmland due to steepness, rockiness, shallow profiles, and moderate to rapid 40 inch runoff, making them best suited for natural upland forests and limiting their value for agriculture or intensive land uses. This analysis shows that the current land use as a natural reserve is an appropriate use for this area.