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the case for green infrastructure

Written by Jenny Janis, Project Manager

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Rain gardens at The Denizen

Urban environments are struggling to manage the influx and flow of stormwater in complex, highly developed domains. This article argues in favor of applying green infrastructure to mitigate the associated challenges.

With the rise of ‘climate weirding,’ predicting the weather has become more of a challenge than ever before. In Texas, the range of annual climate measurements has always been extreme and annual rainfall amounts have a lot to do with that. Total rainfall per year often varies from drought conditions to a wet year. While it’s not clear if annual rainfall amounts are changing, analyzing individual storm events reveals single rain events are becoming stronger. What does this mean? It means that more rain is falling in one rain event, whereas previously it had been dispersed throughout multiple rain events.

Cities like Austin that have experienced a surge of development in a relatively short time-period, are particularly impacted by large rain events. New development leads to increases in impervious cover that result in faster and stronger water flows. What this leads to is changing floodplains and flooding in areas previously not susceptible to floods.

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Rain gardens at The Denizen

Due to the dispersed nature of development the solution is complex. There is not enough space for large detention basins in the city. What’s more, as development increases, basin size increases as well, and detention basins are not the best use of land. Inserting green infrastructure throughout a watershed at varying scales is a first step to mitigating the negative effects of development.

In the book, Green Infrastructure: A Landscape Approach by David Rouse and Ignacio F. Bunster-Ossa, green infrastructure is described by scale of application. “At the city and regional scales, it has been defined as a multifunctional open-space network. At the local and site scales, it has been defined as a stormwater management approach that mimics natural hydrologic processes.” Why is this better than installing bigger pipes to send water rapidly downstream? The traditional solution is expensive, temporary and one-dimensional. Working with natural flows of water reaps many benefits including aquifer recharge, healthier landscape, cleaner water as well as reduced demand on existing pipe infrastructure. You’ve heard the term “Think Globally, Act Locally”? Well, in the case of green infrastructure to mitigate flood risks, the term could be “Think Regionally, Act Within the Watershed.” Doesn’t have the same ring, but the effort is just as worthwhile.

So, what does green infrastructure look like? At the site scale, the Denizen located in Austin is a private development that incorporated rain gardens into open space. Designed by dwg. the linear rain gardens run parallel to site circulation cleansing stormwater as well as providing a landscape amenity for residents. In addition, the Denizen offers a community garden and dog park, utilizing open space for its residents while limiting the amount of impervious surface.

CLICK HERE to learn more about The Denizen

At the city scale, The Greater New Orleans Water Plan is an example of watershed planning that views every road corridor, park space, utility corridor and remnant space as potential holding area for stormwater. New Orleans is the extreme example of a city in need of managing stormwater with elevations levels below sea level. However, the comprehensive and cohesive nature of its Water Plan is a great example for other cities interested in storm resiliency and smart approaches to stormwater management.

CLICK HERE to learn more about the Greater New Orleans Water Plan