Illinois State Water Survey (ISWS) engineers are bringing county floodplain maps into the 21st century, from two-dimensional paper products to digital illustrations using the latest geographical software and technology. The updated, online maps are easily accessible to community stakeholders for use in reducing the risk for flood damage.
Floodplain maps, called Flood Insurance Rate Maps (FIRMs), depict areas that are most at-risk for flooding. Maps are used for regulatory and flood insurance purposes, as well as to identify hazardous areas.
In Illinois, most FIRMs are outdated, some by as much as 20 years, according to Sally McConkey, manager of the ISWS Floodplain Mapping Program. FIRMs need continuous updating to reflect scientific studies and natural environmental changes.
New floodplain maps are based on aerial photographs showing current residential and commercial development.
"ISWS staff realize that where they draw that line to indicate floodplain areas affects people," McConkey said. "If residents and businesses have no warning that they are in a flood zone, they may not have adequate insurance to mitigate damage. On the other hand, those who are located outside of the floodplain area don't want to pay for flood insurance that they won't need."
In 2004, the Federal Emergency Management Agency began funding Illinois' map modernization efforts, in part to support a flood insurance program that is more closely aligned with actual risk and to improve citizens' flood hazard awareness. ISWS, which has been the repository for Illinois floodplain maps since the mid-1980s, started with five county projects in 2004 and now receives $2 million annually, working on more than 20 county maps at any given time.
The 25-staff team partners with the Illinois Department of Natural Resources, Office of Water Resources. Together they collaborate with community representatives and city engineers to obtain up-to-date information, develop online maps, and plan outreach efforts for the public to introduce new county maps. Future plans include helping communities to develop disaster mitigation plans.
To date, ISWS has initiated or completed 58 county maps for Illinois, many of which are available on the web site, www.illinoisfloodmaps.org. Eventually, the team will produce floodplain maps and flood insurance studies for most Illinois counties.
Floodplain maps influence decisions on floodplain policy, new building development, and insurance. Homeowners and business owners who are currently housed in floodplains may purchase flood insurance and take other precautions to reduce their risk of loss, such as elevating homes and/or utilities, and flood-proofing structures. Community ordinances usually dictate that new buildings in floodplains must be elevated or flood-proofed.
"Flooding is the most predictable natural hazard," McConkey said. "Floodplain maps serve as a warning that significant flooding could occur in certain areas, and it's best to be protected against possible damage."