Water scarcity is a profound challenge for designers of the built environment. Beyond looking for water sources and creating sustainable ecosystems, how can we begin to create cities and buildings that will help us to celebrate and mitigate hydro-logical concerns? Hadley and Peter Arnold, co-directors of the Arid Land Institute (ALI) at Woodbury University, have decided to tackle this problem around Los Angeles. With the support of the World Water Forum and the Metropolitan Water District of Southern California, they recently developed a high-resolution geospatial model to strategically identify and quantify the potential for improving storm water capture within urban areas.
The modeling project, “Where is it? Let’s reuse it,” was designed to recognize that maximizing recovery and reuse of rain and stormwater will be central to establishing a robust localized water portfolio for any drylands city seeking to buffer the effects of climate change. Their study focuses on one watershed within the larger Los Angeles basin: the Upper Los Angeles River Watershed Area, also known as the San Fernando Valley. Modeling the valley at the scale of rooftops, roads, curbs, parking lots, concrete, asphalt, and compacted earthen materials, they analyzed three critical datasets and constraint layers. It gives an understanding of how water moves through the basin: where it comes from, where it’s going, at what rate and volume. The model suggests that over 90,000 acre-feet of storm water runoff could be harvested in the San Fernando Valley, enough to sustain almost 100,000 households at current usage rates.
The Arnolds state: "The model can guide our efforts to capture local water in precisely identified zones by applying particular landscape design strategies. Neighborhood by neighborhood, street by street, lot by lot, the model tells us where effort and investment are best targeted for specific hydrologic functions using low-impact best management practices such as vegetated swales to slow and direct the movement of stormwater runoff, detention basins to store water, and urban forests to absorb water. Notably, the model clearly tells us that “infiltrate everywhere” is not an advisable strategy. Some parts of the valley are appropriate for capturing and storing water. Others will work well for moving water from one place to another. Some areas could filter water. Others could be used to allow the water to percolate into the groundwater aquifers in the valley. And others—particularly where groundwater is contaminated—should be avoided until they are cleaned up."
As Los Angeles embarks on a comprehensive redrafting of its zoning laws, the Arnolds' model can give new ideas about twenty-first-century drylands urbanism. By working with people from a variety of sectors, the Arid Lands Institute is hoping to bring people together to re-imagine ways of organizing metropolitan landscapes and create localized models for living with water scarcity — not just in LA but around the world.
Check out more about the full water modeling story here.
Hadley and Peter Arnold are founding co-directors of the Arid Land Institute (ALI) at Woodbury University in Burbank, California. Hadley and Peter were Bogliasco Fellows in the spring of 2000, and, since then, their research on contemporary and historic water infrastructures of the west has continued to attract widespread attention. They have taught multiple history and theory seminars on landscape, infrastructure and urbanism in arid lands, and their design work has been recognized by Los Angeles's MAK Center for Art and Architecture; the LA Architecture + Design Museum, and the AIA/LA.