Houston has always had a damp history. In 1836, the Allen Brothers famously pitched the wharf-anchored town as, “handsome and beautifully elevated, salubrious and well-watered.” Well watered, indeed.

Downtown Houston in the flood of 1935.

Hurricane Harvey has brought a distribution of rainfall and destructive intensity and that again highlights the Achilles heel of Houston’s infrastructure: the lack of developmental oversight and facilities to protect the integrity of its communities. It has, however, reminded us of our strengths — the ever-present tenacity and grit that our citizens possess, and their endless capacity to galvanize in the face of adversity. First responders and good samaritans alike have saved thousands throughout this entire storm and volunteers have flocked to shelters and have waited hours in lines to donate their time, food, and supplies. “Houston Strong” has become a banner that has catalyzed this city to lift and support our neighbors.

How Harvey’s flooding is different

This storm also reveals an unappreciated aspect of catastrophic flooding. This flood was not a fight against an unstoppable storm surge against levees or sea walls, to keep water out of the city (like Katrina) — but a citywide fight to allow the force of storm water generated by rain to go through our metropolis. Typically, when a catastrophic storm barrels towards the coast, the concern is toward the rising tide of coastal waters and devastating winds, and the cities in these areas design to this. However, the Houston area is threatened by its inability to convey rainwater in a well-controlled way from our homes and buildings due to development.

In short, Houston is a threat to itself. The prosperity that we enjoy in this city, as demonstrated by our burgeoning population and the constantly expanding bounds of development, is a double-edged sword.

When we pave our prairie-lands, replace our naturally-absorbent local flora with crisp, manicured St. Augustine lawns, and skimp on meaningful drainage requirements for development — we are building a ceiling that this beautiful, scrappy experiment called Houston can not grow beyond. There is a natural capacity to the land on which we live, and we may have begun to experience what it feels like to approach it.

How does development affect flooding?

During a typical rainfall event, natural surfaces have a built-in capacity to temporarily slow and store water. After an extended duration of rain, the surface eventually becomes water-logged, and water flows more rapidly across the surface.  When natural, porous, surface is replaced by an impervious surface — such as concrete, asphalt, and buildings — rainfall flows quickly as soon as it hits the ground. In order to accommodate this, we design stormwater systems that detain or slow the flow of this water, directing it into regional drainage facilities such as bayous, channels, and reservoirs that eventually lead into the Gulf.

(Source: Thomas B. Shea / AFP / Getty Images)

Obviously, Hurricane Harvey is not a typical rainfall event, so our drainage facilities reached capacity in short order. When these facilities overflow, we utilize streets, roads, and highways as a contingency to store and convey storm water. This is not unintentional. It is a design feature of our public infrastructure, for emergency purposes.

But what happens when the “emergency” overflow of storm water becomes a common occurrence, with destructive flooding repeated annually, if not more often?

This is where our public agencies must face the erroneous fundamental approaches in planning and development. Efforts have been made before, but those singular, loosely coordinated efforts by different levels of government have not been effective.

After the Memorial Day Flood in 2015 and the Tax Day Flood in 2016, our public works officials vowed to find a path toward sustainable flood prevention. However, there are no number of task forces or flood “czars” that can affect the imperative, life-saving changes Houston requires, without proper funding and buy-in from developers.

A deeper look at our storm water regulations

The prevailing design philosophy in Houston focuses on designing storm systems to meet pre-determined amounts of detention volume calculated by the amount of impervious cover or using generalized ratios. These shortcut values often miss the mark of even the most conservative hydrologic assessments. This is not sufficient to characterize the amount of storm water management realistically needed by a given area — particularly when these “detained” flows hit storm pipes, streets, and paved channels that carry water at high-velocity downtown, and into the bay.

Drainage facilities are struggling to keep up with the capacity produced by our consistent storms. We have large assets, such as the Addicks and Barker-Cypress Reservoirs, managed by the Army Corps of Engineers (USACE) — but even they are limited in their effectiveness because they are skirted by single family homes which cap the amount they can store.

The rainfall experienced during Harvey created a nightmare scenario in which the dams had to be opened during the storm, further flooding a city already desperately under water. Unfortunately, the capacity of these reservoirs cannot be increased by building a higher levee or dam, because we’ve boxed them all in with development.

Addicks Reservoir pool elevation over the duration of Hurricane Harvey (Source: harriscountyfws.org)
Barker-Cypress Reservoir pool elevation over the duration of Hurricane Harvey (Source: harriscountyfws.org)

The path forward

We must hold developers and design professionals accountable to produce accurate hydrologic design models, using data for multiple storm events, rather than over-simplified ratios. We must also encourage new development to adopt innovative storm water designs that more closely reflect how stormwater behaves when the land is in its natural state.

The facilities that Houston’s storm water empties into are overdue for major investment. This has begun with high-profile long term initiatives such as Project Brays, with funding from USACE and the Harris County Flood Control District, but these measures alone are not able to deliver fast enough. We must call upon our County commissioners, our municipalities, our utility districts, and our legislature for directed assistance, and programs to bolster our drainage systems.

A commitment to sustainable storm water infrastructure and flood prevention must inform every regulatory level decision from this point forward. Flooding is clearly a pervasive and unfortunate aspect of our environment, but we need not accept catastrophic destruction of private and public property as our “new normal.” Major rainfall events will continue to flood streets, highways, and green spaces, but no one or their neighbor should ever fear for their home, place of business, or life while it does.

“Houston Strong” must be more than a rallying call for supporting each other through this crisis — it must also drive a strong push towards enduring, efficacious change in storm water management after the waters recede.

Cover photo source: Katie Hayes Luke / NPR.