- Spring Creek Channel Improvements - Bonner Springs
The City of Bonner Springs, Kan., undertook its largest capital improvements project to date. As part of the sanitary sewer improvements project, a portion of Spring Creek was improved through a residential area to alleviate flooding.
Channel improvements were undertaken to alleviate frequent flooding of homes, overtopping of streets to repair erosion problems in the bottom and banks of the channel between Metropolitan and Morse avenues. The existing channel lacked sufficient capacity to convey flow for runoff events having a return period of more than two years. Analyses also indicated that adjacent homes started flooding when the 25-year event was reached.
A hydrologic analysis was conducted to estimate flow rates through the channel. The U.S Army Corps of Engineers’ runoff modeling program HEC-1 was employed to model the runoff for the 24-hour duration storm events of 2, 10, 25, 50, and 100 years, and the event for four-tenths the probable maximum precipitation (0.4 PMP) for existing and ultimate land use conditions.
The channel between Metropolitan and Morse avenues was modeled using the Corps’ HEC-RAS for the 25-, 50- and 100-year condition flows. Construction of channel and culverts capable of conveying the required design flows proved infeasible due to the size and cost of the required channel. The most cost-effective solution was to construct a regional detention basin upstream of Metropolitan Avenue with channel improvements downstream from the detention basin to Morse Avenue. The construction of the detention basin provided sufficient attenuation to protect the homes from the 100-year flood and to protect culverts and bridges from overtopping at the 50-year event.
The channel improvements varied by location along the channel. In general, the improved channel consisted of an 8-foot-wide flat bottom, 2:1 (horizontal:vertical) side slopes and a two-foot depth. The bottom and side slopes were armored with 21 inches of rip rap. The 2:1 side slopes transition to a turf-lined bench section to form the channel overbanks. The rip rap-lined portion of the channel acts as a low-flow channel. Where horizontal constraints limit the project, rock-filled gabions were used as retaining walls. Riffle pools were incorporated into the design to promote fish habitat.
The project also involved the replacement of existing reinforced concrete box (RCB) culverts under Lakewood Road and Metropolitan Avenue. New culverts were sized not to overtop at the 50-year flood event.
The detention basin design was based on Kansas Department of Water Resources (KDWR) criteria and the City of Bonner Springs design criteria. The top of the detention basin embankment was 12 feet wide, and the dam side slopes were constructed at a 3:1 slope. The basin was designed as a dry-bottom basin and incorporated with a 4-foot by 4-foot RCB as the principal spillway. The basin was designed to store runoff from the 100-year event and release water at a rate less than the 10-year event. Due to the high discharge velocities through the principal spillway, an energy dissipation structure was designed for the downstream end of the principal spillway to return the discharge velocities to below erosive levels.
Both the channel improvements and the detention basin required permitting from the Kansas State Board of Agriculture, Division of Water Resources, and the U.S. Army.
In addition to design phase services, Burns & McDonnell provided construction phase services, which included bid review, shop drawing review and resident representative services.
- Channel improvements
- Culvert replacement
- Detention basin design
- Hydrologic and hydraulic modeling
- Floodplain permitting
- Construction phase services
- Bid review
- Shop drawing review
- Resident representative services