Pine Forest Subdivision Drainage Analysis

Katy, Texas

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Costello developed a hydrologic and hydraulic analysis for the Pine Forest Subdivision analysis and design of drainage improvements. Pine Forest is an older, large lot subdivision that was developed before floodplain standards were adopted. As such the internal drainage system of roadside ditches and outfall channel to Cane Island Branch was undersized to handle even moderate rainfall amounts. Additionally, the internal system is restricted by backwater flooding from Cane Island Branch stream.

Costello developed an unsteady XP-SWMM model of the existing ditch system and underground storm sewer within Avenue D to determine the existing level of service of the system. The hydraulic model was then utilized to determine both channel and storm sewer improvements to provide a 100-year level of service for the system and to demonstrate no adverse impacts to Cane Island Branch by mitigating the flow increases resulting from the improvements with a regional detention pond.

A final technical report was prepared and presented to the City and Brookshire-Katy Drainage District for both review and approval. Construction plans were developed based on the drainage design and construction of the project was sustainably completed in November 2019. Throughout the project, Costello provided multiple resident and city public meetings to present the existing drainage conditions, results of the drainage analysis, and the proposed improvements.

Relevant Project Services

  • Flood reduction project
  • Hot spot analysis
  • Channel and storm sewer design

Project Size and Cost

  • 127-acre drainage area
  • 2,400-LF of channel improvements
  • $3.8MM construction cost

Unique Project Attributes

  • XP-SWMM unsteady modeling

Challenges Faced

  • Multi agency coordination
  • Public outreach
  • Limited right-of-way for improvements

Resolutions & Results

  • Combination channel/storm to fit within existing easements
  • Redirection of storm water


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