- Dogtooth Bend Nonstructural Mitigation Plan
- Middle Fork Structure Flood Damage Assessments
- Big Five Levee System Emergency and Evacuation Plan
- Middle Mississippi River Flood Prone Structure Inventory, Phase 2
Levee Breach Preparedness Sid Simpson Levee System and Evacuation Plan
A levee breach analysis of the Sid Simpson Levee System including inundation and travel time mapping for possible breach locations was conducted. The intent of this analysis was to inform flood event emergency management planning efforts, improve evacuation planning, and reduce future life and safety risks.
IDNR Upper Mississippi River Communities Inundation Mapping and Risk Assessment
The State of Illinois- IDNR- Office of Water Resources created a library of Mississippi flood inundation maps at different stages for 13 communities along the Mississippi River in Illinois which are not protected by levees. The interpolated flood maps were created so that 1-foot increment stage readings at the nearest river gauge could be mapped at a community using the hydraulic river profiles developed by the Corps of Engineers for their Flow Frequency Study and LiDAR-based topography. The mapped inundation shows flooding extent and depths important to emergency responders. This project utilizes first floor/low entry information to develop a database of structural flood damage assessments for each of these communities associated with the foot by foot inundation mapping or stand alone structures. The information was provided to these communities as a web based product and/or as a pdf booklet depending on the capacities of each community. This project added another completed component to growing statewide risk assessment database being developed and utilized by the state of Illinois.
The data collected in this project was added to the Structures at Flood Risk (SAFR) website. Access to the website must be requested from ISWS.
Lower Wood River Emergency Action Plan and Evacuation Plan
An Emergency Action Plan (EAP) was developed based on a centralized coordination of emergency operations. While Wood River Drainage and Levee District is responsible for the local response for all emergency response activities related to their flood risk reduction infrastructure, resources and components in various jurisdictions’ with complimentary emergency response roles and responsibilities would remain in effect within the operational area. Overall coordination of response efforts should be maintained through a centralized system, even as the response efforts escalate to a multi-jurisdictional level. Important multi-jurisdictional partners include Madison County Emergency Management Agency, the U.S. Army Corps of Engineers – St. Louis District (USACE), local municipalities, and Illinois Emergency Management Agency (IEMA).
The Illinois Department of Natural Resources Office of Water Resources (INDR-OWR), the Illinois State Water Survey (ISWS), and the U.S. Army Corps of Engineers (USACE) Silver Jackets Program collaborated to develop structure-specific risk assessments across Illinois. A structure-by-structure risk assessment provides information that identifies which structures flood, what frequency of flood impacts each structure, the depth of flooding, and the expected losses associated with each event. Answers to these questions help a community understand their flood risk and strategically plan where and how to best deploy resources to anticipate and reduce flood risks. Local responders can use the information to identify where, when, and how severely structures may flood. Structure-specific flood risk assessments completed in Illinois through this collaborative effort are made available on the Structures at Flood Risk (SAFR) website. The intended audiences for the website are state and local officials and agency staff and, in particular, floodplain managers, mitigation officers, and city planners. Access to the website must be requested from ISWS.
Rock Island Co. Structural Flood Damage Assessment
The USACE Rock Island District, Illinois Department of Natural Resources, Office of Water Resources and Illinois State Water Survey partnered to examine Rock Island County flood risk. This inter-agency project developed and communicated structure-based flood risk assessments for the County, completing maps for Rock Island County communities to better communicate flood risk and help plan for future flooding. Structural flood damage assessments were developed for all areas in the floodplain that are considered to be at risk based on annual flooding statistics. These assessments are developed using various flood depths and include survey data collected from the lowest elevation water can enter a building and first floor elevation for all residential, commercial and industrial structures. Parcel data, Geographic Information System (GIS) data, and any elevation certificate data are obtained from the county and each community.
The Illinois Silver Jackets team developed an easy-to-use flood response “map book” for the Sid Simpson Levee District. The information and data visualizations collected in the book support decision-making by officials, facilitate communication, and improve interagency coordination for a more efficient flood response. The book includes information such as flood impacts, datum conversion factors, as-built engineering drawings and river gage information, as well as interior drainage layouts, soil information, and a contact list for local officials. Maps of the entire drainage area show features such as levees, floodwalls, pump stations, and relief wells, as well as aerial photography, evacuation routes, emergency services, and locations of critical infrastructure. These disparate bits of information, when compiled into a single, easily accessible source like the map book, become a useful tool for prompt and accurate response to flooding situations. The map book was most recently used during the near-record Illinois River flood event in May 2019.
Jersey County, Illinois, Modified Loss Avoidance Study
The study calculated the cumulative losses avoided due to mitigation since 1993, including the nine major storm events. The study relied on a modified version of the Federal Emergency Management Agency’s (FEMA’s) Loss Avoidance Study methodology to compute the return on investment of financing more than $14 million in flood hazard mitigation. Advanced geospatial and hydraulic modeling was relied on to overlay high-resolution historical flood depths with an inventory of mitigated structures to determine the losses avoided for each of the nine major storm events. Historical mitigation data was provided by the projects partners, which included Jersey County, Illinois Emergency Management Agency, and Illinois Department of Natural Resources. The study concluded that a cumulative two dollars and 89 cents of losses avoided for every one dollar of mitigation investment for the combined nine storm events that spanned from 1993 to 2017. Additionally, an event of the size of the Great Flood of 1993 occurring today would be expected to yield a total of approximately $17 million in losses avoided for the Jersey County study area. The 289% return on investment should be taken into consideration when county officials, state floodplain administrators and the public are evaluating responsible uses of tax funded initiatives and grant programs to reduce flood impacts.