Estimated Flood-Inundation Mapping for the Blue River, Indian Creek, and Dyke Branch in Kansas City, Missouri

Project Summary

In the interest of improved public safety during times of flooding, the USGS (U.S. Geological Survey), in cooperation with the city of Kansas City, Missouri, completed a flood-inundation study in 2008 of the Blue River in Kansas City, Missouri, from the USGS streamflow gage at Kenneth Road to the mouth, of Indian Creek from the Kansas-Missouri border to its mouth, and of Dyke Branch a tributary to Indian Creek to determine the extent of flood inundation from flooding on the Blue River, Indian Creek, and Dyke Branch and from backwater inundation from flooding in the Missouri River for selected stages above flood stage. The results of this study spatially interpolate information provided by USGS gages, Kansas City ALERT (Automated Local Evaluation in Real Time) gages, and the NWS (National Weather Service) flood-peak prediction service that comprise the Blue River flood-alert system and are a valuable tool for public officials and residents to minimize flood deaths and damage in Kansas City.

Specific objectives of this project were to hydraulically model two complex reaches of the Blue River between 63rd Street and Blue Parkway and between Hickman Mills Drive and 63rd Street to provide water velocity magnitudes and direction and stage elevations in two dimensions; and to create and provide access to real-time inundation/water-depth maps and forecast peak inundation/water-depth maps on the world-wide web for the Blue River in Kansas City, Missouri.

Much of the lower Blue River flood plain is covered by industrial development.  The Blue River and Indian Creek basins are also the location of large parks and recreational development. Bicycle, pedestrian, and equestrian trails exist or are planned for the entire length of both streams. Rapid development in the upper end of the watershed has likely increased the volume of runoff, and thus the discharge of flood events for the Blue River. The NWS issues peak-stage forecasts at nine gage locations in the study area during high water. The small drainage areas of the Blue River and Indian Creek basins causes rapid flooding and allows minimal time for flood forecasting and response.

The first phase of the study, completed in 2007, determined the extent and character of inundation in the Blue River valley from flooding on the lower Blue River from the mouth upstream to Gregory Boulevard. A two-dimensional depth-averaged flow model, FESWMS Flo2DH, was used to simulate flooding within a 2-mile, complex, study reach of the Blue River between 63rd Street and Blue Parkway. Hydraulic simulations of the study reach provided design and performance information for proposed hydraulic structures and channel improvements, extent of inundation, and the areal distribution of water velocity and flow direction. To produce flood inundation maps for the study reach, boundary conditions for high flows were calculated using an existing lower Blue River Hydraulic Engineering Centers River Analysis System (HEC-RAS) model. A secondary HEC-RAS model was constructed and calibrated to extend stage elevations from the upper end of the lower Blue River HEC-RAS model near the mouth of Brush Creek to the upstream face of the lower Blue Parkway Bridge. The constructed HEC-RAS model was calibrated to the discharge measurements. Discharge values associated with stage at the lower Blue Parkway Bridge were selected from the simulated rating curve and input into the two-dimensional model. Two-dimensional flood inundation simulations incorporated design plans for the proposed Blue Parkway Bridge over the Blue River and Union Pacific Railroad. Twelve velocity magnitude and direction profiles were produced for the reach just downstream from 63rd Street, the middle of the study reach, and the reach just upstream from the lower Blue Parkway Bridge.

Flood profiles of the Blue River were developed from stage elevations and slopes calculated between Gregory Boulevard and 63rd Street from high-water marks from the flood of May 19, 2004, between 63rd Street and Blue Parkway from two-dimensional hydraulic modeling conducted for the study, and between Blue Parkway and the mouth from the lower Blue River HEC-RAS model. Twelve maps were produced at 2-ft (foot) intervals from 750 to 772 ft at the Kansas City, Missouri ALERT gage at Blue Parkway to approximate the range of river stages from the 2- to 500-year flood frequencies. Missouri River backwater inundation profiles from flood stage to the highest historical stage were developed using Missouri River stages at the mouth of the Blue River. The USGS gage on the Missouri River at Kansas City, Missouri, is the reference gage for maps of Blue River backwater inundation caused by flooding on the Missouri River. At the mouth of the Blue River a Missouri River stage elevation of 730.9 ft was used as the lowest flood elevation for generation of backwater inundation maps. This river-surface elevation corresponds to an elevation of 738.4 ft at the USGS gage on the Missouri River at Kansas City and a stage of 32 ft. Twelve backwater inundation maps were produced at 2-ft intervals to include the historical range of Missouri River stages above flood stage for the Kansas City area.

The second phase of the project began in 2006 and addresses the portion of the Blue River from 63rd Street upstream to the USGS gage at Kenneth Road, Indian Creek from its mouth to the Kansas-Missouri border, and Dyke Branch, a tributary of Indian Creek. A depth-averaged flow model FESWMS Flo2DH was used to simulate two-dimensional steady-state flood flows within the 5.6-mile hydraulically complex reach of the Blue River between Hickman Mills Drive and 63rd Street . Model results provide maps of flood-inundation extent, flood-plain water velocity, flow direction, and depths for existing flood-plain.  Flood profiles between Hickman Mills Drive and 63rd Street were determined using the two-dimensional flow-modeling.

Upstream from Hickman Mills Drive, water-surface elevations at each gage or forecast location were extrapolated across the flood plain along cross-section lines oriented perpendicular to the downstream direction of the Blue River flood plain. Flood-profiles were developed from water-surface elevations using FEMA (Federal Emergency Management Agency) flood frequency discharges and 2006 stage-discharge ratings at USGS streamflow gages. Flood-profiles of Indian Creek between the Kansas-Missouri border and the mouth were developed from water-surface elevations calculated using current stage-discharge ratings at the USGS streamflow gage at 103rd Street and water-surface elevations derived from FEMA flood-frequency stage-discharge relations. Flood-profile slopes of Dyke Branch between the Kansas-Missouri border and the mouth were developed from water-surface elevations calculated using water-surface elevation slopes derived from FEMA flood-frequency stage-discharge relations. Mapped flood water-surface elevations of other small tributaries to the Blue River in the study area were set equal to the flood water-surface elevations of the Blue River at their mouths for all Blue River water-surface elevations. Thirteen maps were produced at 2-ft water-surface elevation intervals from 763.8 to 787.8 ft at the Kansas City, Missouri ALERT gage at 63rd Street to approximate the range of river stages from the 2- to 500-year flood frequencies. The water-surface elevations at the Kansas City, Missouri ALERT gage at 63rd Street between 763.8 and 785.8 ft correspond to the water-surface elevations at the Kansas City, Missouri ALERT gage at Blue Parkway to ensure consistency with flood maps developed in the first phase of the study.

To provide public access to the information presented in this report, a World Wide Web site (http://mo.water.usgs.gov/indep/kelly/blueriver) was created that displays the results of two-dimensional modeling between Hickman Mills Drive and 63rd Street, estimated flood-inundation maps for 13 flood stages, the latest gage heights, and National Weather Service stage forecasts for each forecast location within the study area. The results of a previous study of flood inundation on the Blue River from 63rd Street to the mouth also are available. In addition the full text of this report, all tables and maps are available for download.

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