Fourmile Creek Watershed: Flood Plain Mapping

Flood Plain maps:

Flood Plain mapping is important for various reasons. For agriculture, it's important to know what areas may inundate from time to time, possibly reducing crop yield. For home owners, it's important to know not only what your risks are, but some localities require you to have flood insurance as a result, and the premiums for this can be high. It is important for understanding water flow, especially when it comes to nutrient loads, sewage runoff - mostly older systems - and other sources of pollution into waterways. Des Moines established a flood-program buyout plan back in 2018 following a major flood event to purchase land back from homeowners at 110% of the assessed property value. There are also projects in place to both reduce the amount of nutrient run-off into the watershed.

The city of Ankeny, one of the areas in which the Fourmile Creek flows, established the "Ankeny Plan 2040" in 2018, highlighting a plan for various aspects of the growth of the town including topics such as the Environment, Population & Growth, Transportation, and Infrastructure, among 10 other chapters regarding the future of the city. Chapter 4: Environment covers extensively future plans for essentially all things watershed, including vegetation management (buffers, native species, riparian zones), and storm water management, providing an excellent summary of watershed management in Ankeny.

For an even MORE in depth study of Fourmile Creek, Snyder & Associates, Inc. conducted a Fourmile Creek Watershed Study in 2013, assessing numerous aspects of the stream, stormwater management properties, and land management.

Below, I have utilized Iowa's Flood Hazard Maps on their website - 'Iowa Flood Information System' to take screenshots of the flood plain. For more information on the system, see an earlier blog post I wrote on the topic.

(Image Sources: Screen shots taken from Iowa Flood Center Mapping Online via https://ifis.iowafloodcenter.org/ifis/newmaps/hazard/)

I zoomed in specifically on a section in the northern part of the watershed with housing nearby highlighting the use of flood plain mapping in development. I've also enlarged the Legend to highlight the various delineations. The top image is a portion along Fourmile Creek surrounded by residential neighborhoods. The bottom image shows flood plain delineations.