Did sand mining exacerbate flooding during Hurricane Harvey?

9 August 2018 (Last Updated August 9th, 2018 10:00)

In the wake of the devastating flood damage caused by Hurricane Harvey, politicians and community groups have criticised the oversight of the sand mining industry along the San Jacinto River. However, a white paper produced by the Texas Aggregate and Concrete Association has countered that the industry’s activities have had the opposite effect. Which side has it right?

Did sand mining exacerbate flooding during Hurricane Harvey?
Stockpile of East Fork Mine in floodway shows considerable erosion after Harvey. Stockpile is taller than the tallest trees which commonly reach a height of 100 feet. Credit: Courtesy of Rehak

Hurricane Harvey swept through the US in September and August 2017, causing $125bn worth of damage and taking 88 lives in Texas alone. Harvey was a once in a thousand years flood event, with more than 60in of rainfall, causing rivers to overflow as floodways and reservoirs failed under the strain of the sheer volume of water.

In Texas, shops and houses were destroyed as chest-high flood waters filled towns and cities. As the water receded in the weeks following, it left 200 million cubic yards of debris for the people of Texas to deal with.

Following Hurricane Harvey, the sand mining industry that has boomed along the San Jacinto River has come under fierce criticism. Protestors, environmental groups and state officials have argued that operating within the floodways reduced the river’s capacity to hold the surge of water.

Sand mining has taken place in Texas for almost half a century, but in the last decade the population and consequential increases in construction and infrastructure have caused something of a ‘gold’ rush. Cities such as Houston now sprawl over more than 1,500km2 and local sand has been used in the construction.

In the US, sand mining is also being driven by the energy sector. The dramatic rise in the use of hydraulic fracturing, commonly called fracking, has opened up billions of barrels of oil and trillions of cubic feet of natural gas since the technology came of age in the 1990s. As the process has grown in prominence so has the need for sand, significantly driving up sand mining operations as each large well requires up to 1,000 trucks worth of sand.

There are 25 sand mines and other aggregate processing facilities along the San Jacinto River, which flows from Lake Houston. Hurricane Harvey flooded more than 16,000 homes and 3,300 businesses in the Lake Houston area alone. Eleven months on from the devastation of Harvey and still only half of the residents who were flooded are back in their homes.

But is sand mining partly to blame for the flooding along the San Jacinto River?

Reducing mining, reducing flooding

Some of the fiercest and more vocal criticisms of the sand mining industry along the San Jacinto River have come from the Reduce Flooding group, set up following Harvey by Kingwood resident Bob Rehak. Sand mines, says Rehak, increased the flooding in several ways.

“With one exception, all area sand mines have chosen to locate, at least partially, in floodways. Some are entirely in floodways,” he says. “That means they are in the main current of the river during floods. At the peak of Harvey, that current carried 150,000ft3 per second down the West Fork of the San Jacinto River where miners had exposed almost 20 square miles of sand in the floodway.”

However, Rehak’s objections are not limited to the position of the mine sites, but also the safety precautions taken by the mines. “One mine, whose dikes have repeatedly broken, leaves only 40ft of unvegetated sandy buffer between operations and the river. Its dikes are not sloped like best management practices recommend,” says Rehak.

“As a consequence of ignoring best management practices for setbacks, buffer zones, slopes and vegetative erosion controls, the dikes in that mine have broken repeatedly. Floodwaters go over and through its dikes, washing sand downstream. That sand then constricts the carrying capacity of the river, reduces the river’s gradient and blocks drainage ditches. In these ways, sand mines contribute directly to flooding.”

The build-up of sand along the river and its effects on the flooding caused by Hurricane Harvey are clear. The US Army Corps of Engineers has been brought in to help dredge the river and ensure it does not overflow again. The corps will extract an estimated 1.9 million cubic yards of sand and sediment.

“Partially as a result [of opening flood gates on Lake Conroe], one particular sand dune that the Army Corps of Engineers expects to begin dredging next week grew 1,500ft in length and 12ft in height in one day during Harvey,” explains Rehak. “It completely blocked a drainage ditch that empties the western third of Kingwood. More than 650 homes and a high school that depend on that ditch flooded. Result: more than $250m in damages. Did all of that sand come from mines? No. Did mines contribute? Yes.”

Sand mining’s mitigating effects

This perspective has been contested by the Texas Aggregate and Concrete Association (TACA), which claims that the industry actually lessens flooding. Its recent white paper, Societal and Environmental Benefits of Sand and Gravel Mining claims that sand mines, far from being responsible, held the water, reducing flooding.

“These facilities that are operating have a number of excavations that have been made during mining, what they actually do in contrast to what people were stating is that they stored quite a bit of that floodwater and helped to prevent additional flooding and sedimentation as that was happening downstream,” says TACA CEO David Perkins. “We felt like it was important to help set the record straight, in terms of really what is the sand mining industry and what does it do for that region.”

Perkins continues that it was mainly due to a breakdown of communication and the proliferation of misinformation that has led to this outcry. It is this, in part, that the white paper seeks to change, along with opening a dialogue for the sand mining industry to be more involved with flood management in the future.

“Just for example one 60-acre pit, that’s 100ft deep, holds 6,000 acre feet of water,” says Perkins. “We’ve got some great potential capacity for off-channel storage that we could incorporate into our mining activities. So we want to have that discussion and see what we can do to be proactive, working in a public/private manner to create a better longer term outcome.”

The San Jacinto River is 45km long, running from Lake Houston all the way to Galveston Bay. As with any river it picks up sedimentation along the way and a study by the Texas Water Development in 2011 showed that Lake Houston had lost 21% of its capacity since it was impounded in 1954 due to sediment accumulating in the lake and San Jacinto River.

Speaking at a community meeting in Kingwood in June, Army Corps Engineer Michael Garske said 65% of the sand clogging the river most likely came from Cypress Creek, which joins the San Jacinto’s west fork. “The banks [of Cypress Creek] are sloughing off and falling in,” Garske said. “That’s where it came from.”

Changing sand mining for the better

Pinpointing the source of the sediments that clogged the San Jacinto and built up banks would be incredibly difficult. But it is clear that whatever the source of the sand, it contributed to the flood in the Lake Houston area and precautions need to be taken.

But could sand mining work to protect Texas from flooding in the future? According to Perkins, there is a lot of potential for the industry to work together with the local and national government to dredge the river in a way that both reduces the risk of flooding and provides and economically beneficial biproduct.

This is true for the dredging being undertaken by the Army Corps, ensuring the resulting material does not go to waste. “Their original proposal was basically just to take this material out of the river and just place it back into a couple of old open pits that are right along the river,” says Perkins. “A lot of that stuff is useable commercially, it’s very valuable. So what we’re proposing to do is to utilise a different spot of land along the dredging project and ultimately take the material, dewater it, separate out the finds and the non-usable material, but then pull out the usable sand material and take it to our facilities to process and use it – as opposed to just throwing it in a hole where it may get eroded back into the river at some point.”

Rehak argues that the sand mining industry in Texas still has a lot to learn about operating safely. In particular, in following best management practices and learning lessons from other states. “Louisiana has an excellent guide to best management practices for sand mining,” says Rehak. “It’s clear, concise, candid, well written and well-illustrated. It was developed by government and industry working together and clearly lays out the dangers if best practices are not followed.”

To reduce the effects of flooding, there should be best management practices that establish a minimum setback between a mine and a river and restrict mining at all in floodways.

Sand mining is a contentious issue around the world and unsustainable practices can have truly devastating effects on the immediate environment and surrounding communities. The San Jacinto River failed to cope with the magnitude of Hurricane Harvey, but with efforts from the TACA, sand mines and the local community – supported by strong regulation – there is hope for the future.