Paving Over the Bayou: The Economic and Policy Case for Permeable Cities

When it rains heavily in a forest, the ground is able to soak up the water like a sponge. Though, in Houston, the asphalt and concrete grounds that cover the city stop rain water absorption and instead cause flooding. How can we fix this runoff problem without inhibiting city growth?

Stormwater collecting in a drain after a period of rainfall

There are two main types of infrastructure that come into play with stormwater: gray infrastructure and green infrastructure. Houston has abundant gray infrastructure, meaning it has human-engineered drainage systems and many concrete elements. Though, these primarily concrete surfaces are impervious, so water cannot soak into the dirt. This allows the rainwater to flow rapidly into storm drains and bayous instead of absorbing back into the ground. Moreover, the water that collects in drains after a storm isn't just pure rain; it's a mixture of rainwater, dirt, pesticides, fertilizers, grease, bacteria, and debris. The new mixture results in not only pollution of local bodies of water, but also an overwhelm of drainage systems and therefore flash floods.

In order to solve this problem, we must look at some of the prompting factors that influence Houston's gray infrastructure development. In order to expand the municipal tax base, city leaders push commercial development. Though, developers prefer cheaper asphalt parking lots over expensive green retention spaces. Every square foot of these paved parking lots increases the burden on public drainage pipes paid for by taxpayers. So, we must work to incentivize green design for developers in order to prevent reactive stormwater damage spending. One solution that cities can use is impervious cover fees to effectively encourage developers to switch to green infrastructure. Instead of charging property owners a flat rate for drainage, the amount of paved land a commercial business owns is taken into account. So, a shopping mall with a large asphalt parking lot would pay a higher monthly fee that a store with grassy retention basins. The issue with these fees lies in the political resistance from local business groups, who argue that they don't work to prevent the development of gray infrastructure; they instead drive commercial investment to neighboring municipalities with fewer regulations.

Conversely, Environmental Impact Bonds can maximize funding for green infrastructure while minimizing taxpayer expenses. Quantified Ventures, an LLC that designs financial funding models that target resilient infrastructure, pioneered the Environmental Impact Bond, or EIB in 2016. They worked with DC Water to fund a $25MM green stormwater infrastructure project that included the construction of permeable pavement, green roofs, and landscaped retention facilities. The bond was privately issued to Goldman Sachs and Calvert Impact Capital to successfully reduce stormwater runoff into Rock Creek by 20%. This "pay-for-success" funding model is what Houston must adopt to incentivize green design and ensure that the financial burden on taxpayers is ultimately reduced. This way, large green spaces can be funded without huge financial risk and usage of emergency cash reserves as well. The city need not rely on the developers to want to build green infrastructure, they can rely on investment firms or eco-focused funds to create the spaces to reduce stormwater runoff. Furthermore, these green spaces can function as neighborhood parks or recreation centers, improving Houston's community and urban planning as well.

Due to the high reactive cost of stormwater flooding damage and its relevance to Houston, Bayou Barrels focuses its efforts on stormwater runoff reduction in particular. We use gallons diverted from municipal storm sewer systems as a metric to measure impact, and we tailor our demonstrations to educate rain barrel users on localized stormwater flood mitigation. With your continued support, Bayou Barrels can grow and educate others about important local issues in order inspire a more flood-resilient Houston.

Sources:

• “DC Water Environmental Impact Bond.” Quantified Ventures, www.quantifiedventures.com/dc-water. Accessed 31 July 2026.

• “What Is an Environmental Impact Bond.” Quantified Ventures, www.quantifiedventures.com/what-is-an-environmental-impact-bond. Accessed 31 July 2026.