Storm Drain Infrastructure and Urban Flooding in Los Angeles


Los Angeles Storm Drains Development, 1910-2010

Los Angeles Storm Drains Development, 1910-2010 from Steve Duncan on Vimeo.

This map– centered on downtown Los Angeles, the historical center of the city– shows the growth of underground storm drains as they have replaced the many natural small waterways and drainage routes that were part of the landscape prior to urbanization.

The red lines show the storm drains. In this map, only the underground storm drains are shown, ranging from round pipes only 18 inches in diameter up to vast tunnels more than 20 feet wide and 20 feet tall.

In addition to the underground tunnels depicted here, Los Angeles also has more easily-visible above-ground waterways like the Los Angles River, which today is a concrete-lined, open-channel storm drain. (Usually it is called a “flood control channel.”) Those very obvious above-ground channels, however, probably lead many people to believe that most of the the city’s drainage and flood-control infrastructure IS visible aboveground.

As this map shows, there is quite a lot more underground. This invisible network of infrastructure has helped to shape neighborhood growth, differential real-estate values in different parts of the city, and the overall patterns of urban development and flood-risk valuation over time.

Los Angeles is often thought of as an arid, desert environment, requiring water to be imported into the city. In the 19th century, however, there were many above-ground springs and streams that flowed year-round and the underground aquifer, or water table, was very close to the surface in the broad, flat plans that stretched between the Los Angeles River and the Pacific Ocean (today’s downtown Los Angeles, Koreatown, West LA, Santa Monica, Venice, etc). Many of these tunnels shown here replaced those former above-ground streambeds so that when rain did come in its occasional torrential bursts, the water would quickly flow out of the city and to the ocean so that new houses and real-estate would not be inundated.

As urbanization progressed in the 20th century, more land was paved over and became impermeable to water: roads, driveways, and houses themselves. Thus SAME AMOUNT of rain would produce MORE AND MORE run-off water, because those occasional but heavy rainfalls could not be absorbed into the ground. Instead it all became run-off and inundated the surface of the city. In this way Los Angeles itself has created the problem of flooding…

More drains were built to carry the increasing water away to prevent floods. At the same time, the drains themselves carried the water through impermeable tunnels and prevented it from soaking into the ground and recharging the water table. Over time, and particularly in the period of about 1890-1940, the former year-round springs and streams dried up, and wells became useless. Thus Los Angeles, bizarrely, managed to create a desperate water shortage for itself at the same time as it was increasing the threat of flooding!

This is a remarkable and remarkably complicated historical story, but it is similar to patterns and problems in many cities through the 20th and now 21st century. How can cities address these problems, and deal with urban water issues in realistic, productive, long-term ways? I think making the hidden infrastructure that has been involved urban development more visible might really help more people to understand just what exactly is going on under their feet.


Underground Storm Drain development near downtown Los Angeles, 1890-2010

Underground Storm Drain development near downtown Los Angeles, 1890-2010 from Steve Duncan on Vimeo.

This movie shows development of storm drain tunnels (gravity mains only) in Los Angeles from 1890-1910, focusing on portions of the Ballona Watershed (Koreatown and West Los Angeles) and the Los Angeles River watershed (downtown Los Angeles). The Los Angeles River is visible as a blue line running vertically in the right side of the image, and the beginning of the open channel of the Ballona Creek as it exists today is visible as a narrow blue line extending horizontally from the left side of the frame. The different widths of the blue lines showing storm drain tunnels is representative of the sizes of the drains themselves, which range in size from approx. 1.5 feet in diameter up to 24 feet wide in the area shown here.
Until the early 20th century, Ballona Creek and its tributaries were open perennial streams extending through much of this area west of the 110 Freeway, and many of the early tunnels constructed were built around those natural channels.
Note: This visualization is based on cartographic data from Los Angeles County. Because of gaps in the attribute information in that data, this shows only about 75% of the total mileage of storm drain gravity mains in this region; however the general distribution is representative of the total extent that exists today, and this this animation of development over time is broadly accurate in its representations of the general patterns of this infrastructure development. Data visualization created by Steve Duncan, 2011.

East Harlem Esplanade Access notes

This shows the areas within pedestrian range of 1/4 mile (green) and 1/2 mile (blue) from the Esplanade, including the length of the pedestrian bridges over the FDR. This shows a much smaller range of areas within these distances than is indicated by the simpler buffer map that looks at linear distance only. Distances on this map are based on paths available to pedestrians.


This map shows areas within a distance of 1/4 and 1/2 mile from the Esplanade access points, measured linearly from the access point (beginning of pedestrian bridge.) However, it does not take into account the non-linear and thus longer routes available to pedestrians. In this map, almost the entire study area is within 1/2 mile of the access points, but when analyzed as a network for pedestrian routes the area within a 1/2 mile walking range is much smaller.


East Harlem showing Pierhead Line – compare to bulkhead line.

East Harlem – waterfront edge is bulkhead line; compare to pierhead line