Blackwater River Background
Highway 23 at Blackwater River, located south of Concordia, MO and north of the city of Knob Noster, MO and Knob Noster State Park connecting I-70 to Highway 50, is regularly overtopped by highwaters, closing the route for a period of time to all users. Closure data has been gathered by local Missouri Department of Transportation officials beginning in January 1973 till present day. On average Highway 23 is closed 28-days per year with an average closure lasting 3.12 days. If the current trend continues, in 2050 the closures could average 40 days per year or more.
Recognizing this major issue, Pioneer Trails Regional Planning Commission applied and was awarded a Missouri Department of Natural Resources Section 604(b) Water Quality Management Grant. Pioneer Trails retained Great River Engineering (GRE) to perform a stormwater study of Blackwater River at Highway 23. The purpose of this report is to determine the existing hydrologic and hydraulic conditions of the Blackwater River and compare them to the historical conditions before the river was channelized in 1910.
The regular closures create hardships on users and the local economy. The detour length is approximately 16.88 miles, taking about 30 minutes. Missouri Department of Transportation’s Average Daily Traffic volume is 2,015 vehicles per day in year 2019 and is projected to be 3,123 vehicles per day in year 2039. Using FEMA’s Benefit-Cost Analysis, the closures are estimated to have an economic loss per day between $54,028 and $83,736. This equates to $1,512,784 to
$2,344,608 in cumulative economic losses in 2019 and $2,161,120 to $3,349,440 in 2050. All dollars are in present-value.
It is evident from the historical research, recent data collection, and the analysis presented in this report that the channelization of the Blackwater River has caused economic distress to the surrounding communities. Also, according to the data and research discussed earlier, the problem is not going to fix itself, and is trending towards increasing economic losses in the coming years. The issue requires a solution that will alleviate the economic stress that the channelization of the Blackwater River has put on Johnson County, and the surrounding region.
Raising Highway 23 approximately 5-10 feet so that the roadway is above the water surface elevation. This option would be of significant cost, but it is the opinion of GRE, to be the best solution to prevent regular road closures due to flooding. Based on preliminary analysis, we recommend this option due to its cost-effectiveness and feasibility.
Potential alternatives can be found on page 11 of the full report.