White Oak Bayou in Houston, TX

HVJ Discovers Unexpected White Oak Bayou Erosion Issues

Project Background

White Oak Bayou Federal Flood Damage Reduction in Houston, Texas

Originating in northwest Harris County, White Oak Bayou is a major waterway that winds southeast, joining Buffalo Bayou at Downtown Houston’s historic Allen’s Landing. In the 1960s, the U.S. Army Corps of Engineers improved the bayou as a flood control measure — drainage performance being critical to protecting Houston during heavy rain events. After the historical deluge of Hurricane Harvey, client CobbFendley needed us to develop slope recommendations in a cost-efficient way.  Working on behalf of the Harris County Flood Control District (HCFCD), they asked if we could utilize some of the previously drilled borings and technical reports and come up with the optimum number of borings to complete the project.

Practice: Geotechnical Engineering

Sector: Water, Wastewater & Flood Control

Location: Houston, Texas

Services: Detention Basin, Erosion Control, Flood Control

Pipe over the White Oak Bayou

The Problem

Our initial task was to determine the optimum number of soil borings for successful project completion and recommend any modifications to ensure the safe functioning of the bayou going forward. A key consideration was how to best utilize the available budget to evaluate the stability of the regraded channel slopes.

The Goal

To perform the work efficiently we needed to leverage as much existing data as possible without missing previously undocumented problems. We were also asked to identify the slope configuration that would meet HCFCD safety requirements.

The Solution

After reviewing existing geotechnical reports, we proposed a lower-cost option that minimized the number of borings and also evaluated the excavated material for reuse instead of importing select fill material so that the project could be  completed within a reasonable budget. We  conducted a geotechnical investigation on-site and evaluated the regraded slopes to meet the minimum required safety factors. Our analysis revealed:

  • For stability, the channel slope should be modified and flattened at numerous locations; we provided several options for channel restoration.
  • When dispersive soils are present along exposed slopes, rainfall and runoff would cause surficial erosion, often resulting in rilling and gullying on the slopes; we provided slope protection and grading recommendations to reduce the impact of dispersive soils.

Our engineers also identified problems that fell outside of our proposed scope of work during our site visit.

These included:

  • Slope failures along the channel caused by erosion
  • Low-flow channels without riprap protection at several locations
  • Numerous examples of toe erosion at the top of an existing low-flow section, primarily near the outfalls that were also without riprap protection.

Applying HVJ’s extensive erosion experience, our project team informed CobbFendley of these concerns and recommended a number of cost-effective ways to address them, including:

  • Installation of a geotextile filter conforming to the requirements of HCFCD Standard Specification, Section 02379 beneath stone riprap to reduce soil erosion.
  • Use of stone riprap in areas where high flow velocities are anticipated, such as near outfalls and confluences.

By understanding these issues in advance, we helped CobbFendley plan ahead without derailing budgets or schedules.

Next Steps

HCFCD is set to confirm all governmental stakeholder organizations. Now armed with a more comprehensive set of potential failure issues, project steps, and recommendations, they hope to more quickly acquire the funding needed for the restoration of White Oak Bayou.

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