Presentation on theme: "Tour of Five Small Flood Control Dams in Iowa and Nebraska Rehabilitation Needs of Aging Small Flood Control Dams."— Presentation transcript:
Tour of Five Small Flood Control Dams in Iowa and Nebraska Rehabilitation Needs of Aging Small Flood Control Dams
Over 11,000 small flood control dams have been built in 2,000 watersheds in 47 states since 1948.
These Dams Were Built by Local Sponsors Assisted by the USDA Natural Resources Conservation Service. Authorization for the construction of the dams came from: Public Law (Flood Control Act of 1944) and Public Law (Watershed Protection and Flood Prevention Act of 1953).
The question now is how can sponsors deal with these aging dams that need major rehabilitation? Earlier constructed dams were designed for a 50-year life span. A time that many dams are now reaching. Over one-half of the dams are over 30 years old.
Major Issues With Aging Dams Many of the dams have deteriorating concrete and metal components in the principal spillways and the lakes are filling with sediment. Some are unsafe. Some were designed for rural agricultural protection and now have homes, highways, and other structures downstream. Many sponsors don’t have the funds and expertise to rehabilitate the dams.
What This Tour Is About: The following tour includes scenes and information about five small flood control dams in southwest Iowa and southeast Nebraska. These dams show some of the types of problems and issues that are facing local watershed sponsors across the nation
Tour Map The tour takes place south and east of Omaha, Nebraska
Hamburg Dam M1 Freemont Co., Iowa Project Sponsors: Fremont County Soil and Water Conservation District City of Hamburg, Iowa
Hamburg Dam M1 Hamburg Dam M1 was built in 1962 to control erosion and to help control flooding in Hamburg, Iowa. A school, homes, businesses and hospital are immediately downstream from the dam. Loss of lives is a possibility if the dam should fail. Protecting Urban Areas Hamburg Dam No. M 1
The original cost of the project in 1962 was about $40,000. It would cost about $260,000 if built today.. Hamburg Dam M1 The dam is considered a high hazard structure and was built under those standards.
This project is a good example of the kind of protection and benefits provided by small flood control dams. It also illustrates why sponsors are looking at ways to extend the life of the dams.
Possible Courses of Action Decommission: Upstream grade stabilization and original flooding problems would need to be addressed. Maintain the dam: Continue to monitor the dam and components closely and analyze redesign or replacement of components in the future as necessary Remove/relocate downstream structures:
Pony Creek Dam No. 31 Mills County, Iowa Project Sponsors: Mills Co. Soil and Water Conservation District Mills Co. Board of Supervisors Pony Creek Drainage District No. 2
Pony Creek Dam No. 31 Pony Creek Dam 31 is one of 24 dams built in the Pony Creek Watershed in Mills County, Iowa to stabilize gullies and reduce flooding. The dam was built as a Class A (low hazard dam) in 1963, but in 1974 U.S. Highway 34 was rerouted to run just below the dam, which has changed the hazard classification to a Class C (high hazard) dam. Changing Conditions
A deteriorating spillway pipe now puts the highway in danger of being covered with 2 feet of water if the dam should fail. Replacing the spillway pipe and modifying the roadside to redirect potential floodwaters would eliminate this risk. About 8,000 people travel this section of highway daily. Original cost of dam in 1963 was about $40,000. Today’s cost would be about $300,000 Pony Creek Dam No. 31
Community Benefits The dam protects the Loess Hills from accelerated gully erosion and protects a highway and land below dam from flooding. It is a featured attraction in Mile Hill Park. The 13-acre lake provides opportunities for fishing and hiking. Pony Creek Dam No. 31
Possible Courses of Action Decommission: Upstream grade stabilization would need to be addressed. Rebuild for Safety: Major rebuilding of dam would need to address the disruption of park users, as well as possible damage to high quality woodland and fish habitat. Replace the spillway pipe: Replacing the pipe and reshaping the road right of way will eliminate the concern for dam failure and can be done without major disruption to the site or damage to valuable archaeological sites in the area.
Indian Creek Dam No. 2 Pottawattamie Co., Iowa Project Sponsors: West Pottawattamie Co. Soil And Water Conservation District City of Council Bluffs
Indian Creek Dam No. 2 Indian Creek Dam No. 2 is one of several dams built just above the city of Council Bluffs, Iowa. The 70-foot high dam was built in 1975 as a grade stabilization, full flow structure on a tributary of Indian Creek. Protecting Urban Areas
Indian Creek Dam No. 2 dam is in good condition now. The concern is that as the dam ages, a major storm may result in failure of the dam and massive damage downstream. Indian Creek Dam No. 2
Failure of Indian Creek Dam No. 2 could result in loss of lives and severe damages to private and public facilities. Downstream from Dam
Possible Courses of Action Decommission: Upstream grade stabilization would need to be addressed to avoid return to original gully problems. Rebuild for Safety: If breach studies show the hazard classification should be rated as high, redesign and rebuilding of spillway would be necessary. Remove/Relocate Existing Downstream Structures: If breach studies show only limited structures are in danger, relocation of structures could be an option.
Papillion Creek Dam No. 27 Sarpy County, Nebraska Project Sponsor: Papio-Missouri River Natural Resources District
Papillion Creek Dam No. 27 Papillion Creek Dam No. 27, Sarpy County, Nebraska, is a good example of a dam that was built on farmland and is now surrounded by homes. The dam was built in 1974 at a cost of $74,200 and would cost about $130,000 to build today. From Rural to Urban
This small grade stabilization structure also serves as a sediment trap and has captured about 2.7 acre-feet of sediment. Papillion Creek Dam No. 2
The dam serves as a focal point for an aesthetically pleasing urban neighborhood for those building homes around it. Papillion Creek Dam No. 2
So far no homes are below the dam. The upstream hydrologic conditions have changed and will change more as development continues. Major concerns are corrosion of spillway conduit and the increasing amount of sediment occurring. Local homeowners use the area around the dam as a walking trail and a place to view wildlife and just enjoy the beauty around the small lake. Papillion Creek Dam No. 2
Possible Courses of Action Decommission: Upstream grade stabilization would need to be addressed to avoid return to original gully problems. Rebuilt/modify for safety: Widen the emergency spillway and remove sediment. Remove/relocate downstream structures: There are currently no structures downstream, but future controls may be need to be placed on development.
Brownell Creek Dam No Project Sponsor: Nemaha Natural Resources District
Brownell Creek Dam No is located in Otoe County, Nebraska. It was built as one of many grade control structures on Otoe County farmland. Brownell Creek Dam 13-6 The dam has stabilized gullies and provides modest flood control benefits. There is no pool of water, but it does provide wetland habitat. Deteriorating Metal and Concrete Components
This dam is an example of how metal and concrete components are deteriorating and need replacement. This structure has exceeded its design life, but still serves its purpose of controlling erosion and sediment. Brownell Creek Dam 13-6
Possible Courses of Action: Decommission: Upstream grade stabilization would need to be addressed to avoid return to original gully problems. Replace/modify: Replace the principal spillway, considering a rock chute and remove the sediment. Take no action: This could result in dam failure in the future and lead to same results as decommissioning.
National Rehabilitation Needs An initial survey of states found 2,200 dams need rehabilitating to keep them safe and functioning as designed.
Opportunities Exist Congress has passed legislation that authorizes cost share assistance for rehabilitation and for USDA technical assistance. Pilot rehabilitation projects are underway in five states. Information is being gathered to determine the needs and projected costs for rehabilitation.
In 2001 over 400 Watershed Project Sponsors Indicated an Interest in USDA Assistance in Rehabilitating 1,434 Dams in 35 States. It Would Cost Over $500 Million to Rehabilitate These Dams
To Get More Information About Aging Flood Control Dams and Rehabilitation Efforts: Go to the USDA Natural Resources Conservation Service Web Page: (www.nrcs.usda.gov) Click on to Aging Watersheds.