City of Killeen Valley Ditch Channel Improvements
The City of Killeen faces unique challenges in managing storm water drainage, especially when it comes to streams and ditches that drain from the Fort Hood Military Installation into the City. In particular, the City of Killeen Public Works Department received a multitude of complaints from its residents relating to Valley Ditch. The complaints ranged from minor nuisances to major hazards. Valley Ditch originates on the Fort Hood Military Installation and flows through residential neighborhoods, into the downtown area of Killeen, and terminates at the confluence with Nolan Creek. Valley Ditch was not included in a previously performed, detailed FEMA study.
The Killeen Public Works Department wanted to take a proactive approach to the dilemma along Valley Ditch, and subsequently contacted Walker Partners for help. As a team, the City and Walker Partners worked together to establish a long-term plan of action.
As with many drainage-related studies, the project began by collecting data. Data collection for this particular stream made for an intense process as a large part of the watershed resided on the Fort Hood Military Installation. Since the September 11, 2001 terrorist attacks, information related to military installations is kept under tight wraps and is more difficult to acquire. Walker Partners was able to glean information from as many sources as could be attained and relied on sound engineering judgment to complete the basin study, without actually ever setting foot in the basin. Luckily, a few of the typical sources were still available since they predated the 2001 restrictions. Conventional data sources were able to be utilized to analyze the portion of the watershed from Nolan Creek to the City Limit boundary.
Storm water hydrology and hydraulic modeling were performed for Valley Ditch using industry-standard computer software packages created by the Army Corps of Engineers, HEC-HMS and HEC-RAS, respectively. The existing models served well as a baseline extent of the present-day floodplain. The floodplain was then overlaid onto the City of Killeen’s planimetric maps to show the inundation.
Once the baselines of the existing conditions were established, the real work began – how to improve the floodplain and remove the hazards. A broad spectrum of improvements were evaluated and modeled as possible Capital Improvement Projects (CIPs). Many of the improvements were as follows: off-site regional detention facilities; in-line detention facilities; channel improvements; and culvert improvements. Each CIP item was evaluated based on construction cost and impact to the floodplain. The final study and recommendations are currently being implemented by the City of Killeen, with the goal of filing a Letter of Map Revision (LOMR), upon completion of all the CIPs.
The first CIP project will dramatically lower the base flood elevation, making a tremendous impact to the floodplain within the newly renovated downtown area. The CIPs that are currently planned, as well as the future CIPs along Valley Ditch, will reduce flood hazards, nuisances, and aid the City of Killeen’s local economy in its on-going revitalization of the downtown business district.