Emergency Action Planning



Lake Sherwood

Sylvan Lake EAP Case Study

Missouri Absorbs Inundation Mapping Cost

A traditional breach analysis and inundation mapping for a HHP dam can be a costly expense for dam owners if created by a qualified private engineer. Typically it may range between $10,000 and $20,000 depending on the size of the impoundment and the complexity of the watershed below the dam. As new geospatial and geologic software technologies have come along, the efficiency of producing these studies and maps has increased while the cost has decreased.

Some of this software was developed by the Federal government, particularly the U.S. Army Corps of Engineers and the U.S. Geological Survey. Another major contribution to a scientifically sound inundation study is the availability of high-resolution LiDAR, (Light Detection and Ranging) imaging data captured by laser equipment aboard aircraft. LiDAR data is not available for every county in Missouri, but has been important in developing inundation maps for some of the most populous counties. LiDAR imaging can cut through trees and foliage to reveal very precise ground contours and elevations. DNR engineers have sought partnerships with county governments and other state and federal agencies that could benefit from LiDAR data. Each of these technologies has reduced the need for weeks of time for traditional on-site survey teams in preparing an inundation study.

Missouri DNR's Surface Water Section of the Water Resources Center took the lead in developing the technology systems and procedures for the Missouri inundation mapping program. DNR inundation maps will show downstream structures that would be inundated by at least two feet of water during the time of maximum water surface level. That's enough to wash a car off a road.

"We have calculated that $5,000 is the estimated value of DNR developing a set of inundation maps for a typical dam. This does not include the acquisition of LiDAR data. Some of that data is public domain and some of it has to be purchased. We try to cost-share that expense with other agencies.

In various combinations customizable and suitable for each dam, these technologies can provide detailed, accurate floodplain maps. These maps facilitate the development of preparedness and warning requirements, computations of flood damage, and information to help ecosystem restoration after the water recedes.