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We’re still figuring out how to do development in a floodplain

From the inbox:

The Greater Houston Flood Mitigation Consortium has released dual research reports that examine current standards in the area’s drainage, detention, and development regulations. The reports also include findings that encourage implementation of new and updated flood management infrastructure approaches and regulations to mitigate the risk of future flooding.

According to Consortium Project Manager Christof Spieler, “This research is intended to inform and unite our city and county leadership, development community and residents in planning for our region’s future. Some of the current regulations are not sufficient to address current flood risk and are further compounded by our region’s growth. Taking time to consider how we could benefit from updated regulations isn’t trying to limit that growth, but would set into motion the research and creative solutions required for growing in more resilient ways.”

Research Paper 1: Detention & Drainage Regulations:

According to researchers from Rice University’s SSPEED Center and report contributors Houston Advanced Research Center, as more and more land in and around Houston is developed, runoff and an inability for the land to absorb water from heavy rain events become contributing factors to flooding. The report goes on to identify areas where current detention regulations, which are in place to prevent those negative impacts, may in some situations be allowing new development to increase downstream flooding.

Specifically, the report findings state current regulations, with the biggest impact being from projects of 50 acres or less on greenfield sites:

  • Overestimate the runoff from some undeveloped sites and, as a result, underestimate detention required to maintain current conditions;
  • Use one-size-fits-all drainage formulas that do not reflect the variation in soils, vegetation and topography across the county; and
  • Only address maximum flow rate, not total runoff volume, meaning the cumulative effect of multiple developments can still increase flood levels. Further, downstream flooding can last longer while multi-day events can have a greater impact even if current requirements are met.

Suggestions to improve current regulations:

  • Increase the default minimum detention requirements set by the City of Houston and Harris County Flood Control District for development sites of all sizes to be a more conservative figure.
  • Allow developers / property owners with sites of any size to provide less than the default minimum detention requirements, provided there is an engineering study, based on field operations, that quantifies pre-development runoff.
  • Install gauges to collect measurable data on runoff in a variety of undeveloped watersheds.
  • Commission engineering studies for the undeveloped portions of Harris County’s major watersheds to understand cumulative effects and determine appropriate parameters.
  • Based on the studies, set specific criteria for the watershed, which could be coordinated across multiple jurisdictions in the watershed.
  • Require evaluation of cumulative effects across entire watersheds.
  • Require evaluation of multi-day events (three, five or seven days) as well as storms lasting a day or less.

Research Paper 2: Development Regulations:

According to the researchers from Kinder Institute for Urban Research Rice UniversityTexas Southern University, and Houston Advanced Research Center, the region can embrace a form of growth and innovation that sees opportunities in rules and systems that encourage resilient growth to avoid placing people and property in harm’s way.

Suggested approach for considering new regulations and policies:

  • Create regulations and policies to ensure both residents and officials understand that there is a range of flood risks both in and outside of current mapped floodplains.
  • Create systems that utilize both green and gray infrastructure elements for public and private infrastructure to maximize our ability to mitigate flooding.
  • Create land use and development policies that minimize future risk and address existing issues rather than relying too much on expensive infrastructure projects.

The report points out that these regulations are instituted and enforced by a variety of jurisdictions and operate within a legal framework set by the Texas Legislature. Changing the framework can require actions at many levels, and no one entity is solely responsible. Keeping the above points in mind and considering best practice research, key report takeaways include:

  • Tailor new developments to avoid at-risk areas in such a way as to keep people and structures from harm’s way and to reduce the number of existing vulnerable residents and structures.
  • Adopt regulations that inform residents about their flood risks and their options to mitigate those risks. This information should be proactively accessible to homeowners and renters both in and out of the mapped floodplains.
  • Provide public funding and programming to assist low-income residents in bringing their older, flood-prone homes up to new standards.
  • Require design standards and development permitting to incorporate broader resilience goals to help facilitate a more resilient region.
  • Implement regulations and design standards to encourage both green and gray infrastructure solutions to maximize our ability to reduce flooding. In order to see their use increased, green infrastructure efforts should be incentivized or even required, as the City of Houston is now studying.
  • Successful stormwater and floodplain management needs to be implemented at the regional level with the cooperation of city, county and regional institutions. Stormwater and floodplain management professionals within these institutions are best suited to put into place new and emerging best practices.
  • Balancing economic goals with regulatory reform can be a struggle. As new data and technology reveal a new picture of flood risks for the Houston region, this balance will likely shift, resulting in the need for a new set of regulatory practices. This report summarizes best practices that are potentially relevant for the Houston region.

A link to both reports can be found at  houstonconsortium.org.

flooding, harvey
See here and here for previous research, and here for the Chron story. I don’t have anything to add, I just hope Commissioners Court and the Lege are paying attention.

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2 Comments

  1. C.L. says:

    Coming up on the two year anniversary of Harvey and the eighteen anniversary of Allison and Harris County et al still can’t pull their head off of their collective asses. Pitiful, just Keystone Kops sh**. At some point ‘suggestions’ need to morph into ‘requirements’.

  2. GMcK says:

    I have an easier answer for the question of building in a flood plain: Don’t do it.

    Rebuilding in a flooded area should have a one-strike rule. FEMA has flood-resistance standards, which seem to be unknown around here. If a structure floods a second time, rebuilding that isn’t compliant with those standards should be prohibitied, regardless of detention ponds or other so-called flood mitigation structures nearby. And I say this as a homeowner who was flooded by Harvey.