In late August 2017, Hurricane Harvey made landfall in Texas and caused devastation along the Lone Star State’s coast as well as in Houston and surrounding towns. Current estimates suggest the tropical storm displaced up to 30,000 people, destroyed or flooded over 130,000 residences and claimed the lives of 60 people.
Whereas the hurricane’s strong winds played a large part in wreaking havoc in Texas, the downpour of up to 50 inches of rain in some areas is what caused the most damage. This would have resulted in heavy flooding anywhere, but the factors outlined below greatly exacerbated its effects.
Since the 1980s Houston has been the largest growing metropolitan region in the United States. With no mountains or hills to slow the city’s development, it has sprawled uncontrollably for the past several decades. According to research by Texas A&M, this led to 25,000 acres (10,000 hectares) or 70% of wetlands in Houston’s vicinity to be compacted and paved over.
Previously the wetlands absorbed large quantities of water and drained it into neighboring bayous and ultimately the sea. Now, cemented areas create immense amounts of runoff with no place to go. Even heavy rains during normal thunderstorms can result in flooding in many areas. The disproportionately large precipitation during Hurricane Harvey could only cause catastrophes.
Leaving the wetlands undeveloped would not have avoided flooding altogether. However, combined with other factors, it could have reduced the damages and saved both people’s lives and homes.
Development of Prairie Grasslands
Apart from wetlands, large expanses of prairie grassland have been heavily developed in recent decades. With Houston’s metropolitan area and many other coastal towns steadily increasing in size, the need for new housing developments caused developers to encroach on previously untouched grasslands.
These plains used to function similarly to a sponge and soaked up large amounts of water during cloudbursts. As with the wetlands, their capacity would not have been enough to completely ward off flooding during a hurricane, it would have made a significant difference in protecting homes from inundation and reducing the number of people who needed to evacuate.
Houston, the USA’s fourth most populous city, and much of Texas’ coastal area are built on what is called “black gumbo”. Found around the wetlands, this type of dirt has a thick, mud-like consistency and experts consider it to be one of the least absorbent soil types existing in the US.
While this is not an issue during normal rainfall, this kind of ground cannot absorb the heavy showers occurring during hurricanes. This factor aggravated the situation by causing floodwater to stay in place rather than seeping into the ground.
Development of Bayous
To help drain water and channel it towards the sea, many communities fortified existing bayous with concrete and dug retention ponds. During heavy rains, this helps reduce flooding in adjacent areas but after the hurricane, it created new problems. Retention spaces filled up quickly, water could not drain fast enough and buildings around the pools were flooded heavily.
Conservationists with the Texas Parks and Wildlife Department in Clear Lake City lament the weak protection of wetlands and waterways in Texas. Recent funding cuts for regulating bodies and courts interpreting protective laws very loosely, make it easy for developers to be lax in following rules, to the detriment of nature and wildlife.
With Texas’ coastal area being very flat, flood water can spread easily. To keep homes from flooding, engineers suggest building houses on “pier and beam” foundations, giving the water a crawl space of several feet. Because this is not mandatory and costs several thousand dollars extra, most people opt out of this choice.
Finally, many streets were deliberately built below grade. This was supposed to give water from overflowing bayous and retention ponds a place to go. While this initially protected some homes, it also made it harder for rescue teams to reach certain areas as heavily flooded streets made it hard to get through.
Better protection of the coastal watershed will avoid similar destruction of lives and properties in the future.