Sneak Peak at Results of Kingwood Area Drainage Analysis; Review Before Meeting Tuesday Night

The Harris County Flood Control District has released a Report Summary of results from the 600-page Kingwood Area Drainage Analysis. HCFCD will hold an online community meeting Tuesday night to discuss the results. It may help to review this summary or HCFCD’s before the meeting.

Objective: Protect Homes/Businesses from Bigger Rains

The objective of the Kingwood Area Drainage Analysis: to provide the knowledge needed to protect homes and businesses from flooding in a 100-year (1% chance) rain as defined by the new, higher Atlas-14 Rainfall Probability Statistics. Said another way, the engineers want to make sure that if you bought a home outside the 100-year flood plain, that you STILL won’t be flooded in a 100-year rain. Engineers call that “the 100-year Level of Service (LOS).”

*Steams, ditches and channels evaluated as part of the Kingwood Area Drainage Analysis. Please note ditch numbers for any comments you make as the flood control district identifies them by that number.* *It will help communication.*

What Study Included

To accomplish their objectives, engineers:

Evaluated historical floods and mapped flood damage
Created hydrologic and hydraulic models to quantify flooding risks along streams, channels and open ditches
Identified drainage issues associated with storm sewers and streets
Performed an overland flow analysis
Used LiDAR, record drawings, previous surveys and data collected in the field
Incorporated the impact of potential storm sewer improvements on channel capacity
Quantified detention capacity needed to prevent increasing flows into Lake Houston
Determined how many structures would benefit from each improvement (or planned future improvement)
Researched rights-of-way and flowage easements
Recommended channel-capacity improvements
Recommended bridge and culvert improvements
Developed preliminary cost estimates
Recommended construction sequencing

In places where ditches provide less than a 100-year level of service, storm sewers cannot empty into them during a 100-year rain. When that happens, water backs up into streets and can flood homes. So engineers are looking at the performance of the drainage system from end to end in conjunction with the City of Houston.

Limitations: What Study Does NOT Include

The study does NOT:

Include new topographic surveys
Evaluate improvements for greater than 100-year events
Examine Montgomery County issues except for North Park Drive
Identify sites for detention basins
Duplicate the San Jacinto River Basin Master Drainage Plan or associated sedimentation and sand trap studies

No construction is included as part of this project. This project will only lay the groundwork for subsequent construction projects.

Study Identified Nine Channels That Need Improvement

Not surprisingly, the Kingwood Area Drainage Analysis found that many channels do not need improvements. Said another way, they already provide the required level of service. However, engineers identified nine channels that DO need improvement to protect homes and businesses.

Six of those nine have rights-of-way controlled by HCFCD. They include:

Other entities control the rights-of-way for the three remaining ditches/streams that need improvements:

For summary sheets of each recommended Kingwood Area Drainage Analysis project, click on the associated links. The Taylor Gully project will need to be re-analyzed if the Woodridge Village purchase goes through; that area could turn into a regional detention facility.

This table contains a summary of streams, channel types, ownership, current level of service, improvements, rights of way needed, cost estimates and detention estimates for all the projects considered in the Kingwood area.

Two Projects Recommended Immediately

Based on the results of the Kingwood Area Drainage Analysis, HCFCD recommends two projects: G103-38-00 (Kingwood Diversion Ditch) and G103-80-03.1B (Taylor Gully) move to the next phase: engineering design. Additionally, HCFCD recommends the Taylor Gully project be reanalyzed to determine how the use of Woodridge Village for detention could modify the recommended plan.

These two projects were chosen because:

They help the largest number of people.
HCFCD owns land to expand and deepen the Diversion Ditch.
Diversion Ditch enhancement will immediately take pressure off Ben’s Branch, and help flooding there.

Thus, these two projects address the three biggest needs. The remainder will have to wait for Capital Improvement funds.

First Step of Many

The Kingwood Area Drainage Analysis is a feasibility study that helped identify the problem areas. As you can see from the lifecycle diagram below, it represents the first step of several. The Flood Control District included $10 million in the bond fund (See F14) for Kingwood projects. That can be local-match seed money for attracting state and federal grants.

*Source: Harris County Flood Control. After completion of the feasibility study comes preliminary engineering.*

Online Meeting Details Tuesday Night

HCFCD will hold an online meeting Tuesday night. Engineers will describe the project and recommendations in more detail. You will also have a chance to interact with team members, make suggestions, and ask questions.

Tuesday, October 20, 2020

6:30 p.m. to 7:30 p.m.

Join online at PublicInput.com/Kingwood

Or by phone at 855-925-2801 with Meeting Code: 9541

Please login a few minutes early. The Flood Control District has a brief survey on the login page that will help them track your concerns.

What the Flood Control District Needs from You

The Flood Control District needs to know about local issues that they may NOT have identified near you.

For example, culverts under Kingwood Drive for a ditch near me are almost totally blocked by sediment. That could have affected their analysis. And the stream may have correctable issues that could easily prevent future flooding.

Another example. The recommendations include taking out the low water crossing near Bear Branch Elementary School. Many kids use that to walk or bicycle to school. Removal without replacement would create a major inconvenience. It might also negatively affect downstream bridges damaged in previous storms.

A final example: the study did not recommend any changes to the bridge over Taylor Gully at Rustling Elms. However, many Elm Grove residents identified that as a major issue in two floods last year.

*The Rustling Elms Bridge is a road over twin culverts, not a true open bridge like the one farther downstream in the background.*

Please join the meeting Tuesday night and be prepared to discuss such issues. Volunteer your local knowledge. Speak up now or live with the results.

Credits

The Kingwood Area Drainage analysis cost $700,000. Funds from the 2018 Harris County Flood Bond and TIRZ 10 paid for this study.

Posted by Bob Rehak on 10/19/2020

1147 Days since Hurricane Harvey