September 28, 2016

Bellaire Drainage Study is a Potential Game-Changer

Good decision making and long-term planning start with good information.  Over the past several months the City Engineer has been working on a detailed study, utilizing sophisticated technologies such as 3-D LiDAR surveys, to collect data and develop more accurate storm water modeling.  The dramatic potential of this new information is hard to overstate.  The results of this study may very well reshape the way we think about flooding and drainage, both locally and regionally.

The following is my layman’s summary of the highlights of the study.  For a complete copy of the City Engineer’s report, click here, and for the accompanying presentation slides, here.

Flood Map Revision to Remove Parts of Bellaire from the Floodplain

First, a perhaps surprising immediate impact of the study is that it provides hard data to support a Letter of Map Revision to remove certain parts of the City from the FEMA-designated floodplain.  It turns out, the data shows that the flooding risk for many properties is not as severe as currently rated.  Does that mean you’ll no longer need flood insurance?  Absolutely not.  But a map revision could save Bellaire property owners as much as $3 million per year on flood insurance premiums.  That alone is worth the price of admission (the City paid $45,000 for the study).

More than 80% of the City is in the 100-year floodplain according to the current FEMA flood map.  Our 4,780 flood insurance policies cost Bellaire property owners $5.6 million in premiums annually.

Future drainage infrastructure improvements that further reduce flooding risks can also lead to lower flood insurance premiums, which would help offset the costs of those projects to taxpayers.  Ongoing initiatives in our area, like Project Brays and the Willow Waterhole Greenway, are already producing results.  Indeed, in the coming year the Harris County Flood Control District plans to start the remapping process to document the progress Project Brays has made in floodplain reduction.

Study Recommendations

While the prospect of lower flood insurance rates for many in Bellaire comes as a pleasant surprise, re-rating the flooding risk for those properties is not in any way to suggest that there is no risk.  Obviously we still have a major flooding problem and that’s the focus of the study.

We’re sharing the data we’ve collected with other entities in the region, such as the Harris County Flood Control District and TxDOT.  We’re all in this together, and through this study Bellaire has proactively taken the lead in identifying problems and developing solutions based on good information.

  • The IH-610 drainage system is severely undersized.  The study supports a request to TxDOT to increase the capacity of that system to meet the demand for storm water conveyance to Brays Bayou.
  • In the interim, the drainage system immediately adjacent to the proposed 610/59 interchange project should be improved as part of that work.
  • Utility conflicts within the major north/south drainage systems should be resolved where possible.
  • The study suggests continued collaboration and inter-local agreements with regional partners.

Even as we work towards regional improvements to ensure adequate capacity downstream of us, we still have much work to do on our own local infrastructure.  The most prominent recommendation in the study for local improvements is to upsize the storm sewers in strategic locations from the typical 2-year capacity to a 100-year capacity, not so much for storm water conveyance but to provide significantly greater underground detention storage capacity in the areas that most need it.  In other words, the intended storm water conveyance service level would still be for 2-year storms, but the additional capacity will help collect excess storm water runoff and store it underground.  More storage underground means less water in the streets and less water in the homes of Bellaire residents.


The strategic locations identified in the study include the following drainage systems:

  • Chimney Rock ($1.3 million)
  • South Rice ($2.9 million)
  • IH-610 ($41.1 million)
  • Newcastle ($36.7 million)
  • Railroad system north of Bellaire Blvd. ($2.9 million)
  • Southdale ($0.9 million)

Doing the math, that adds up to approximately $86 million.  The cost to install 2-year systems on those same streets is $30 million, so overall this recommendation would add $56 million to our Street and Drainage program.

That’s a lot of money, but there may be some funding options.  More intensive maintenance of newly installed drainage systems, and rehabilitation of existing systems (much like asphalt overlays rather than total street reconstruction), would help stretch available funding.  That work would be programmed for an anticipated 50-60 year asset life span.  Also, there may be other funding sources for some of the strategic locations identified, in particular the IH-610 system.  Finally, rest assured that we won’t tear up recently-completed improvements (e.g., Newcastle) anytime soon.

The study also suggests addressing the problem of Brays Bayou backing up into our local systems at high water flood stages by installing backflow preventers at major outfalls.

While the study does have the potential to change the way we think about our flooding problem, our basic two-fold approach will remain the same.  We will continue to systematically invest in local infrastructure improvements (the Better Bellaire bond program will be on the ballot this November) while also participating in coordinated regional planning informed by the data.

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