Best Practices

Louisa County, Iowa, #11 Levee District
Example of Non-Structural and Natural Storage

Recurring significant flood events and resultant physical damages to levees throughout the Midwest region have increased interest in implementing non-structural alternatives to levee repairs. Public Law 84-99 (P.L. 84-99) provides USACE with the authority and responsibility to either repair flood-damaged levees enrolled in its levee program or to implement non-structural alternatives to those structural repairs.

Following the Midwest floods of June 2008, the Iowa Interagency Levee Work Group (now Iowa Flood Risk Management Team [Iowa Silver Jackets]) identified and coordinated a precedent-setting non-structural alternative to full repair of the Louisa County, Iowa, #11 Levee District's levee system. The alternative is a combination of over 300 acres of Natural Resources Conservation Service flood plain easements with significantly reduced structural repairs to protect a state highway. The alternative required the cooperation of the levee's public sponsor, the county and state mitigation agencies, USACE and Natural Resources Conservation Service(NRCS) to implement. This non-structural alternative consisted of leaving five breaches in the lower end of the levee system open while repairing two breaches in the upper end of the system. The remaining increment of repaired levee will continue to provide flood deflection benefits for a major county road and approximately 400 acres of agricultural lands within the levee district.

This alternative provides reconnection of nearly 3,200 acres of previously isolated floodplain with the Iowa River as well as increased flood storage benefits to downstream interests; construction is complete. As a result of collaboration, over 1200 acres of formerly protected area was returned to the floodway, gaining not only improved environmental habitat but increase flood storage capacity while continuing to protect an important state road. The NRCS (Emergency Watershed Protection) easements were crucial in the sense that protection of those lands no longer provided benefits to support full structural repair. As implemented, the cost to PL 84-99 was estimated to be $187,000 less than the full structural repair.

The Iowa team was encouraged by this success and is currently working to implement another non-structural alternative with the Green Island Levee and Drainage District at the confluence of the Maquoketa and Mississippi Rivers (downstream of the [former] Lake Delhi Dam). USACE is providing assistance to NRCS in the development of a Wetland Reserve Enhancement Program project proposal request to acquire easements on nearly 1,400 acres of cropland previously protected by the Green Island levee.

back to top

Real Time Flood Inundation Model, Indiana
Example of Outreach (Risk Communication) and Building a Tool to Facilitate Mitigation (Land Use and Non-Structural)

Resolution of seemingly small issues can lead to greater collaboration. Team members were aware of differences between USACE and Indiana Department of Natural Resources (IDNR) data; differing boundaries used in the models produced elevation differences of up to two feet. The Silver Jackets team facilitated resolution, and within a short time, the data were aligned. Without Silver Jackets, neither agency would have pursued resolution. The state sees this as a valuable service; when all agencies can agree on a single set of data, the state mitigation program benefits.

Success in resolving these differences led to a discussion of current needs, and the team devised a real-time flood inundation model. The National Weather Service projections and hydrology from the Advanced Hydrologic Prediction Service are combined with real-time gauge data from the U.S. Geological Survey (USGS). Models create a real-time view of the location and depth of flooding. When overlaid with tax assessment data, construction data, and structural value information for residential and commercial structures, an accurate prediction of potential damage can be calculated, employing the USACE depth-damage curve and Hazards United States (HAZUS0 modeling. Each database/model was written with a different digital structure. Through Indiana and Purdue University, a bridge program was written to draw the individual models and programs together under an open architecture format and allow a person to run the program automatically upon demand in real time.

The program, when river levels reach a set trigger point, will run automatically and provide both current inundation information and predictive information for response and mitigation actions. The project allows emergency management personnel and the public to view current and predicted extent and depth of flooding through a Web portal. The near real-time and forecast flood inundation mapping, in addition to being viewable through a Web portal, will be downloadable in the form of Geographical Information Systems(GIS) files that can be imported into GIS applications such as the Federal Emergency Management Agency's HAZUS-MH hazard mitigation and loss estimation program. The overall cost for the pilot project was $750,000. No one single agency had the funding or the personnel to complete this project alone, yet with the collaboration of skills and funding, the pilot project was created using a minimal investment. The state of Indiana is now planning to utilize recently awarded Community Development Block Grant funds to apply the tool state-wide. The opportunity for major cost savings from damages avoided is tremendous. The effort provides a better predictive capacity, which will assist in zoning and planning, as well as targeting areas for mitigation such as acquisition or elevation.

After talking with the Indiana Silver Jackets team, the Mississippi "Camo" Jackets team has begun a similar effort. While no technical assistance funding is provided by USACE, the project was initiated due to Silver Jackets team collaboration. From a recent press release: The Forrest County Board of Supervisors recently entered into a joint funding agreement with the USGS to initiate a cooperative program for flood inundation mapping with the Cities of Hattiesburg and Petal and the Forrest County Emergency Management District. Flood Inundation Maps show the extent of flooding that is expected over a given area. Through assistance of the National Weather Service, this data is provided online and can indicate which community structures are likely to be impacted by floodwaters. Inundation maps also provide local officials additional information needed to better mitigate the impacts of flooding and build more resilient communities. The first phase of a multi-year flood inundation mapping project will include the USGS evaluation of existing flood models on the Leaf River and the initial construction and instrumentation of a new flood-monitoring site on the Bouie River at Glendale Avenue. The $26,000.00 cost will be shared equally by the USGS and Forrest County, with support from the cities of Hattiesburg and Petal. Hazard Mitigation Grant Program funds will be applied to assist with a portion of the local share. Upon completion of the project, both the Leaf and Bouie Rivers will provide real-time river stage data via the internet during flood hazard events, and local residents and emergency managers will have valuable information for hazard mitigation. Future agreements will fund the annual operation and maintenance of the flood-monitoring sites and the completion of the flood inundation maps. "Forrest County is appreciative for the local communities' partnership to work with state and federal agencies to provide a tool that will help protect the public during flooding disasters," said David Hogan, President of the Forrest County Board of Supervisors.

back to top

North Branch Elkhart River Project, Indiana
Example of Outreach and Watershed Approach to Mitigation Planning

The North Branch Elkhart River Project evolved as the many participating agencies discussed a particular community's recurring efforts to resolve their flood risk management challenges. The community had sought studies and assistance from a number of individual state and federal agencies over many years, but none were coordinated, and little action followed.

The Indiana Silver Jackets team brought together the Indiana Dept of Natural Resources, the Indiana Dept of Environmental Management, the Indiana Dept of Homeland Security, U.S. Geological Survey(USGS), U.S. Department of Agriculture-National Resource Conservation Service(USDA - NRCS) and the US Army Corps of Engineers. Individually the agencies had invested several hundred thousand dollars in studies, stream clearing, snagging efforts, and other work in the area. After each agency reviewed available studies and information regarding the area, the interagency team compiled a single summary document that explained, in layman's terms, the geological and hydrologic conditions, the flood history of the area, and possible approaches to resolve the effects of flooding in the area. The report presented alternatives as well as warnings regarding actions that could exacerbate the situation. The findings were presented to the local steering committee and the community as a whole; public meetings were held to both inform the community and to foster acceptance of the findings.

The community has since reported that they are following the first recommendation, the formation of a basin-wide planning team to examine the options, not from a neighborhood perspective as had been done in the past, but from a watershed perspective considering all communities as a part of a solution. Although there were no direct expenses to funding programs, the agencies invested staff time to research and write the report. Differences in the community were set aside, as the community implements a watershed approach to develop a basin-wide strategy based on common interests. Long-term requests for funding will now focus on a holistic solution rather than individual patches.

back to top

Leveraging programs: Orange County, Indiana and State-Wide LiDAR mapping
Example of Non-Structural (Flood Warning) and Interagency Approach to Mitigation Planning

In Orange County, Indiana, the Lost River flows through a karst environment, often under the surface. Flooding occurs without warning. The Indiana Silver Jackets team has implemented an interagency approach and found a way to create a flood warning system. By linking a number of newly placed U.S. Geological Survey(USGS) stream gages with a USACE Planning Assistance to States Hydrology and Hydraulics study of the underlying karst features below the communities, the community will receive automatic triggers when the water reaches levels corresponding to previously observed flooding.

With the help of US Department of Housing and Urban Development 's Community Development Block Grant, the community will provide $75,000 for their cost-share and will conduct Light Detection and Ranging(LiDAR) flyovers. Community Development Block Grant (CDBG) is by its nature a federal grant that loses its federal identity when granted to the state and its sub-grantees. The CDBG has received special supplemental funding to assist communities that were damaged during the Midwestern flood disasters of 2008. Thus the community will receive the work with minimal investment and the documentation provided will not only benefit this specific project for the community, but also will benefit future mitigation projects. The system will warn the community of impending floods thus saving thousands of dollars in damages. Through Silver Jackets, the state will be able to acquire LiDAR mapping for all 92 counties, leveraging interagency funds to map 12 counties and $13 million in CDBG funds to map 80 counties.

back to top

Marietta, Ohio
Example of Outreach (Risk Communication) and Non-Structural (Flood Warning and Backflow Prevention)

The Ohio Silver Jackets have optimized use of data and resources of many state and Federal agencies. Coordination through the Ohio Silver Jackets team enabled the small community of Marietta to acquire detailed mapping of its community by tapping into an ongoing regional watershed study. These maps are used daily by the City. Through the same Silver Jackets team, the USACE Planning Assistance to States (PAS) program provided $60,000 in initial resources to develop the City's first Flood Hazard Mitigation Plan. USGS, Ohio Emergency Management Agency, Ohio Department of Natural Resources and USACE presented mitigation concepts, short- and long-term mitigation recommendations in public meetings and cable news. Completing the Flood Hazard Mitigation Plan enabled the city to gain eligibility for FEMA flood mitigation funds. Partial implementation of the Flood Hazard Mitigation Plan was achieved when the City obtained a $180,000 Community Development Block Grant grant from US Department of Housing and Urban Development for "duckbill" backflow prevention for several storm sewer outfalls at the Ohio River. Also in the Marietta area, the team was able to leverage USACE Section 205 funds to implement a flood warning system. Through Silver Jackets, the Corps funded project will utilize U.S. Geological Survey stream gages downstream and Ohio Emergency Management Agency rain gauges upstream. Relationships established on the Silver Jackets team were essential in developing a plan for co-locating USGS stream gauges and Ohio EMA rain gauges. For a total project cost of $375,000, cost shared 65/35, life saving rain and stream gages will be installed for early flash flood detection and warning.

back to top

Revised 29 June 2011