In July of 1996 and February of 1997 Kane County experienced serious
flooding. 16.9 inches of rain fell over Aurora in less than 24 hours in
1996. This is the second highest rainfall ever recorded, anywhere in the
country, outside of areas affected by hurricanes. Despite the fact that
heavy rainfall was limited to the southern portion of the County, flood
stages on the Fox River were very high – exceeding the 100-year stage in
Aurora. Flooding was even more severe along some of the smaller creeks
whose watersheds are primarily in southern Kane County. Essentially all
of these creeks experienced record high stages. The stage on Blackberry
Creek in Aurora exceeded the 500-year stage published in the flood
The February 1997 flood was much different than the July 1996 event.
First, the rainfall, while large, was nowhere near as great as in July.
The rainfall during the February event was on the order of 3.0 to 3.5
inches which is between a 2-year and 5-year rainfall. However, the rain
fell on snow covered and frozen ground causing significant runoff and
streamflows which had frequencies rarer than would be suggested by the
frequency of the rainfall. In many areas of the County (particularly
northern Kane County), the February event produced higher stages on the
Fox River than the July event.
Comparing the July and February events illustrates the variety of
mechanisms and conditions that produce large flood events. In general,
smaller urban watersheds will respond most to short duration (on the
order of a couple of hours), high intensity rainfalls. These types of
rainfalls typically are the result of summer thunderstorms. Large
watersheds such as the Fox River will generally respond to either long
duration (on the order of days to weeks) and widespread (geographically)
rainfalls and/or to snowmelt events. These types of events typically
occur in spring.