River Trending Down
I've taken a look at the current and predicted Missouri River conditions. It should be noted that the flow from the Gavin's Point reservoir (which is the main upstream reservoir from Chesterfield) was increased to 160,000 cubic feet per second (CFS) a couple of weeks ago. That increased flow is already reflected in our current and projected river levels. The Corps has indicated that they expect to maintain this discharge through the middle of August. There are no plans to increase the discharge from Gavin's Point that I am aware of.
Contrary to what it may sound like, "Flood Stage" does not infer there is any flooding or properties in danger. Flood stage is simply a gauge reading indicating that the river has exceeded its normal high channel levels. If you happen to drive over the Daniel Boone Bridge, even though the river is at flood stage, you'll notice that it is still wholly contained within the river channel and as much as a half mile away from the Monarch Chesterfield Levee.
As you can see from the chart below, the St. Charles gauge (which is approximately one-half Day downstream from Chesterfield Valley) was read at 27.2 feet at 9:30 am this morning. It is projected to slowly trend down for the next several days. These projections Included expected\predicted precipitation for the next 24 hours. There are no current or pending threats for the City of Chesterfield associated with riverine flooding from the Missouri River.
As you can also see from the chart below, the Hermann gauge which is approximately one day upstream from Chesterfield, was read at 24.96 feet as of 9:30 am this morning and is also expected to trend down over the next several days.
Just to get an idea of what is occurring several days upstream, I have included the hydrograph for the Kansas City Gauge. It read 32.05 this morning, was expected to rise another tenth of a foot to crest at 32.2 later today, then trend downward for the next several days.
The National Weather Service and Corps of Engineers also collaborated to develop a "likely range of flows and river stages" for the Missouri river, which reflect precipitation in the Missouri River Basin in the next couple of months at the high and low range of normally expected precipitation. That collaboration indicates that the range of maximum gauge stages at St. Charles could range between 29 and 37 this season. Please recognize that these are statistical models and are intended to simply project the impacts of normal or higher than normal precipitation added to the existing river flows. Simply an effort to determine the level of threat, such that communities are aware of the potential for flooding.
By way of comparison, the Great Flood of 1993 crested at an elevation of 40.1 feet at St. Charles. Since that time, the Monarch-Chesterfield levee has been raised and improved dramatically. I would also point out that the agricultural levee has not been overtopped since 1995. The agricultural levee is generally described as a ten year levee. Under normal, average conditions, we would expect the agricultural levee to overtop on a ten year average frequency, at a reading between 33 and 34 on the St. Charles Gauge.
For a more recent comparison, Herman crested on September 17th of 2008 at 28.9 feet, and St. Charles crested at 31.74. The Agricultural levee was not overtopped and water barely reached the toe of the levee on the west end. Every event is unique and has its own set of conditions, but this should provide a reasonable perspective.
That being said, it is also important to understand the difference between riverine flooding and flash flooding. Given the saturated ground conditions and seemingly continuous rainfalls, small waterways, creeks, and tributaries are subject to flash flooding. Localized intense rainfalls can cause such waterways to quickly rise, flood, and inflict dramatic damage. Please be aware of the dangers of flash flooding. If you encounter flooded roads or standing water, do not attempt to drive through the water. Find another route. As little as 6 to 8 inches of water can lift and float a vehicle. If the water is flowing, it is even more dangerous. Avoid creeks and waterways when possible.
I hope this information is useful.
