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Q&A with HCFCD on Ben’s Branch Flooding Issues

After St. Martha’s Catholic School and Kids in Action almost flooded on a two inch rain earlier this week, I asked Harris County Flood Control a series of questions about Ben’s Branch. The questions covered a variety of topics. They included the Kingwood Drainage Assessment; flood mitigation alternatives along the creek; preservation of natural amenities; a maintenance agreement with Friendswood and Bear Branch Trail Association; timing for all of the above; and more.

St. Martha’s school on Tuesday after two inches of rain

Harris County Flood Control District continues to be a paragon of openness and transparency. Below: detailed answers to the questions people have been asking.

Q. Ben’s Branch is included in the Kingwood Drainage Assessment. When will that study be complete?

A. Our consultant is scheduled to submit the Draft Feasibility Report for HCFCD review in May 2020. We plan to hold a public meeting by early 2020 to present preliminary results and then a second meeting to present final results and recommendations for future actions.

Q. Will the consultant report findings on creeks “as they go” (one by one) or deliver one summary report at the end? (The concern: that they could sit on recommendations for months that might prevent flooding in the interim.)

A. We do not envision the alternative analysis to be completed on a creek by creek basis, but we are working to identify some initial projects that could be recommended for implementation prior to completion of the report.

This assessment is to determine level of service and make recommendations for projects to move into preliminary engineering once this assessment has concluded. Some projects might require partnerships to implement.

Q. I understand that you are close to reaching a maintenance agreement with Friendswood for the natural portion of Ben’s Branch between North Park and Kingwood Drive. Can you send me a copy of the proposed maintenance agreement or, as a backup, summarize the key features?

We are seeking an easement from the Bear Branch Trail Association, with a waiver from Friendswood Development Company, to perform desnag activities for stormwater conveyance purposes on the portion of Bens Branch between Woodland Hills and Kingwood Drive where we currently have no property rights; that is, from approximately 1,500 feet downstream of Woodland Hills to approximately 3,000 feet upstream of Kingwood Drive. Please go to the Interactive Maps of Kingwood Assessment Area on our website and look at the fuchsia line along Bens Branch on the “Channel Right-of-Way in the Kingwood Area” map.

We will share the easement language once it has been finalized.

Q. How long have you been working on this easement?

Since October 24, 2018.

Q. How will this easement differ from your normal easements?

We are obtaining this easement to perform desnag activities to allow the free flow of stormwater. For information about our desnag operations, please visit our website https://www.hcfcd.org/hurricane-harvey/kingwood-information/hcfcd-vegetation-management-activities/.

When Friendswood Development Company granted fee ownership of this portion of Bens Branch to the Bear Branch Trail Association, they retained certain rights and set specific restrictions on the property that would make it impossible for HCFCD to perform its necessary flood control responsibilities.

This agreement is different because the Friendswood Development Company wants to restrict HCFCD’s rights to “widen, deepen, enlarge, straighten, or smooth the channel in such a way as to increase channel capacity.” 

HCFCD has been working to negotiate the right to enter this property and complete channel maintenance operations for drainage purposes, while still maintaining the aesthetics that are important to both the Friendswood Development Company and the Bear Branch Trail Association. HCFCD will request the right to review plans for future improvements placed within the channel (e.g., bridges and low water crossings).

HCFCD cannot allow activities that could increase the risk of flooding where we spend public dollars.

Q. What were Friendswood’s concerns?

They wanted no alteration of the channel geometry and to retain the ability to add trails, bridges, and other structures without obtaining permits from HCFCD.

Q. Will the maintenance described in the agreement be enough to restore conveyance of Ben’s Branch so that it doesn’t flood surrounding homes and businesses?

We plan to perform desnag operations to remove obstructions so that stormwater can be conveyed efficiently.  HCFCD can’t guarantee that flooding won’t occur in surrounding homes and businesses.  HCFCD can selectively remove vegetation along the banks and other debris in the channel to increase the capacity of the channel to convey stormwater downstream.

Q. What will it take to avoid flooding? Said another way, what obstacles do you face in restoring conveyance?

Before we can perform these activities, we need to have property rights and the ability to safely access the site.

Q. What would Harris County Flood Control prescribe for Ben’s Branch to protect people from flooding?

We have not formally begun our process to identify alternatives; however, we expect to explore these alternatives for the Bens Branch channel:

  • Expanding the Kingwood diversion ditch from 150 feet to approximately 300 to use more of the right of way. Because the Kingwood diversion channel diverts water from the Montgomery County portion of the upper Bens Branch watershed, and there appears to be available capacity in the diversion channel, we will look into whether diverting more flow down the diversion channel would result in reduced flows along Bens Branch. Please note that we anticipate that this option would require a stormwater detention basin along the lower limits of the diversion channel.
  • Effectiveness of building stormwater detention basins in the upper Bens Branch watershed (Montgomery County side). This will only be feasible if large undeveloped tracts are identified for possible future basins.
  • Evaluation of channel conveyance improvement needs along the entirety of Bens Branch. Some improvements may need to be considered on portions of the channel within which HCFCD has no legal authority to work.  If this is the case, HCFCD would coordinate with the property owners to determine what improvements could be completed.

Q. Are there compromises that would provide protection from flooding without destruction of the natural amenities which residents also value? I realize this may involve a discussion of degrees of protection.

As part of this study, HCFCD will be identifying alternatives to provide 100-year level of protection within the channels, using the rainfall rates from the newly adopted Atlas 14. These alternatives will identify the magnitude of improvements necessary to handle approximately 18 inches of rainfall runoff in a 24 hour period.

There are times that flood risk reduction competes with natural and public amenities; when that occurs, HCFCD works to minimize impacts to natural amenities. Once alternatives are identified, Kingwood Area residents will have a chance to voice their opinions and concerns with our alternatives. Please note that at some point it might become necessary for the Kingwood community to decide between higher levels of flood protection and maintenance of existing amenities.

Q. Do you have any idea yet why St. Martha’s and Kids in Action almost flooded on a one year rain? What has changed in your opinion?

We do not have any formal findings as to the potential causes for the excessive ponding along Bens Branch near the Kids in Action / St. Martha’s area. The intensity of the rainfall contributed to the ponding; inlets are typically designed to handle approximately 1” per hour, and when the rainfall intensity exceeds this, there is ponding in streets and parking lots.

It also appears that there may be a downstream blockage since extremely slow velocities were seen in the water in this area and there are much lower water surface elevations in the Bens Branch channel sections further downstream. HCFCD has contacted the Bear Branch Trail Association to ask them to assess their channel and remove any blockages.  

Posted by Bob Rehak on 11/1/2019 with help from Beth Walters of HCFCD

794 Days since Hurricane Harvey and 43 since Imelda