What is the difference between a 100-year and 500-year flood?

A 1% flood is commonly referred to as a 100-year flood and a 0.2% flood is commonly referred to as a 500-year flood. However, this does not mean there will only be one flood of that magnitude in that time frame. The 0.2% chance identifies that area that has a 0.2% chance of flooding each year. The 1% chance identifies the areas that have a 1% chance of flooding each year. Both of these are shown on the Riley County GIS website (see answer for mapping). The 1993 flood closely reflected the 0.2% chance flood modeling on the FEMA floodplain maps. 

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1. Is the evacuation advisory still in effect?
2. Is a shelter available?
3. Is there a plan for door-to-door notification of residents and what messages might they give?
4. How will I know if someone telling me to evacuate is official?
5. Should we mark our house if we evacuate early to let the emergency personnel know that we have left?
6. Why can’t the Corps let out a little water to avoid a large “uncontrolled” release?
7. How much time will the Corps give us before opening the spillway gates or increasing the water release?
8. Do I need to turn off my gas?
9. What areas were affected by the 1993 flood?
10. What is the difference between a 100-year and 500-year flood?
11. Is FEMA updating the 2015 flood maps?
12. Where can I get sand and sandbags?
13. Do you need volunteers?
14. Who can I talk to about building in the floodplain?
15. Who should I talk to learn more about flood insurance?
16. Do releases at Tuttle Creek Lake affect Wildcat Creek?
17. Will the City issue permits to rebuild or repair homes if flooding occurs?
18. Will my power be shut off?
19. What if I return to my residence and find damage?
20. Is there a curfew in place?
21. Are any roads closed?
22. What can I do about mosquitoes?