The Flood Hazard
The most recent flooding along the Little Cal occurred on September 13, 2008. The flood reminds us of the flood risk the river poses. The floods of September 2008 nearly matched the flooding in June 1981. The City’s worst flood on record occurred in November 1990. That year heavy local storms caused the Little Cal to rise higher than before, over half a foot higher than the September 2008 flood. Similar flood levels were reached in December 1982 and July 1996.
Properties in Lansing’s floodplain are subject to three flood problems: over bank flooding, local drainage, and sewer backup. You could be faced with one, two or all three of these hazards.
Over bank Flooding
Lansing is subject to over bank flooding from the Little Calumet River, North Creek and Lansing Ditch. The largest flood problem is along the Little Calumet River. The first major flood in recent memory on the Little Cal was in June 1981. It was followed by a flood almost as high in December 1982. Lansing’s worst flood on record (so far) occurred in November 1990. Heavy local storms caused the Little Cal to rise higher than before, over half a foot higher than the 1981 record. It was estimated to be a “25-year” flood. The July 1996 flood came within inches of the 1981 flood.
Construction of a levee and floodwall on the Little Cal during the 1980’s kept the 1990 and 1996 floods out of town. However, a flood of as little as 2 feet higher would overtop this barrier and cover many blocks. For information on the base or “100-year” flood, contact the Building Department at 895-7193.
Because of all the construction in the upstream watersheds, storm water runs off quickly. The 1990 storm caused over bank flooding to reach buildings in less than 24 hours. The river kept rising for another 24 hours. With our flat terrain, it takes a while for the waters to recede. After the Little Cal crested in 1990, it took 3-4 days to get back in its banks. In other words, the river was out of its banks for a total of five days and in buildings for two of those days. On the smaller streams, such as North Creek and Lansing Ditch, the water rises and falls faster.
Lansing’s local drainage problems are primarily due to backed up combined sewers and storm sewers. The sewers are designed to drain streets and ponding areas along with transporting sanitary sewage to treatment facilities. When they are blocked or overloaded by heavy rains, the drainage system is plugged. Storm water sits for hours or days, waiting for the sewers to clear.
Local drainage problems occur during storms in any part of the Village. In some cases, yard ponding will cause or aggravate basement flooding. Flooded streets and yards can cause or aggravate the health and safety problems and disrupt traffic.
With no place to go, sewers back up and flow into the lowest opening in the sewer line. Sanitary sewers back up into basements and storm sewers back up into streets. An overloaded combined sewer backs up into basements first and, if the water gets deeper, into streets. With the completion of the Deep Tunnel connection in 1996, the combined sewers have been better able to handle their wet weather flows.