PROJECT ALERT NOTICE (IL) Minor flooding in IL as Isaac treks eastward

Date: Sun, 02 Sep 2012 09:20:19 EDT

Summary: Significant rainfall produces only minor flooding in drought-stricken Illinois

Over the last 48 hours, up to 6 inches of rain fell in Illinois in isolated areas, with 3 to 4 inches of widespread general coverage throughout the central and southern parts of the State.

The significant rainfall resulted in surprisingly little runoff. Illinois has been in an extreme drought this summer, with many streams experiencing zero flow (some that had never before been dry). This morning most streams are now in the 'normal' percentile class of flows for this time of year. Only four streams (Little Crooked Cr, EF Shoal Cr, Hurricane Cr, and Sugar Cr) are in a minor flooding category with AEP of less than the 2-year recurrence interval. All four are small, headwater streams that should recede quickly. An additional inch or so of rain is expected today, but should not create any flooding issues.

The rainfall occurred in and around the three major basins in Illinois that were most signifcantly impacted by the Drought of 2012-- the Big Muddy, the Kaskaskia, and the Sangamon basins. All three basins rely heavily on SW for public water supplies, and reservoirs were at crtically low levels. This event will provide much needed relief in and around those basins. Thank you Isaac!

Google map showing IL WSC raingage locations and totals


Sub-Region: Midwest; Region: Central United States