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Catching the Rain:How Green Infrastructure Can Reduce Flooding and Improve Water Quality in Texas
by Elizabeth Berg, Frontier Group and Luke Metzger and Brian Zabcik, Environment Texas Research & Policy Center
Flooding has brought significant damage to Texas in recent years. Unfortunately, continued development across the state, along with the growing threat of climate change, suggests that the challenge posed by flooding is unlikely to decrease. However, we can adapt to it.
Historically, as forests, prairies and wetlands were replaced with development, people built “gray” infrastructure – sewage pipes, drainage tunnels and water treatment plants – to take over the job of water management. However, these systems are expensive to build and maintain, and their construction can produce harmful environmental impacts.
Green stormwater infrastructure, however, can help mitigate flooding and protect water quality, at less economic and environmental cost than gray infrastructure. While green stormwater infrastructure cannot fully prevent flooding, it can limit property damage and water pollution, making these systems worthy of public investment. Flooding is a serious concern in Texas and around the country.
- In 2015, 176 people across the U.S. were killed by floods.
- Texas has suffered more flooding fatalities than any other state in 11 out of the last 21 years.
- Flooding damages across the state totaled more than $3 billion in 2015.
The risk of flooding is increasing across Texas.
- The National Academy of Sciences found that global warming is increasing the frequency of extreme rainfall and other weather-related disasters across the country. This trend is particularly evident in the Texas cities of McAllen, Houston, Austin and El Paso, which are all among the 50 U.S. cities that have experienced the largest increase in heavy rains since 1950.
- The spread of development and paved surfaces, which are impermeable to stormwater, has increased rapidly across the state. Recent satellite data shows that by 2011, 31 percent of Harris County was fully covered by impermeable material. The total area of impervious surfaces in surrounding counties has also increased by 17 to 53 percent since 2001.
Green stormwater infrastructure (GSI) can help limit the property damage and water pollution caused by flooding.
- GSI systems come in many sizes and varieties, and are designed for residential, commercial and public use. Common components include:
- Rain gardens – planted areas that absorb rainwater where it falls.
- Bioswales – shallow, vegetation-lined drainage channels.
- Permeable pavement – a road or surface made out of material that allows water to seep through.
- Green roofs and walls – vegetated roofs or walls that capture rainfall on the building itself.
- Rain barrels – storage containers that collect rainwater from roofs.
- Most types of green stormwater infrastructure can absorb between 50 and 90 percent of rainfall.
Green stormwater infrastructure can be a more cost-effective investment than gray infrastructure.
- For projects with similar water management impacts, construction costs for green stormwater infrastructure are 5 to 30 percent lower than the expense of building new gray infrastructure.
- Maintenance costs, particularly for residential scale GSI, are minimal. Additionally, these systems collect water that can be used for cleaning and gardening, which can reduce water bills.
Green stormwater infrastructure offers positive impacts in addition to flood protection. Additional benefits of green stormwater infrastructure include:
- Restoring the water table. In northern Texas, water levels in the Ogallala Aquifer have dropped nine feet since 2004. Increasing the amount of permeable cover can replenish groundwater.
- Improving water quality. Studies have shown that stormwater systems can trap between 45 and 99 percent of solid pollutants in stormwater.
- Beautifying the landscape. Many green stormwater management installations can be incorporated into new or existing public parks, further benefiting the community.
- Removing greenhouse gases from the atmosphere. Trees and green roofs can capture hundreds of pounds of carbon over their lifetimes.
Investment in green stormwater infrastructure in Texas will require work and support from local and state policymakers. Some important actions include:
- Encouraging new developments to limit impermeable cover and incorporate aspects of green stormwater infrastructure.
- Requiring cities to design green infrastructure programs.
- Preserving nature lands.
- Restructuring local agencies to integrate the management of all water resources.