Road

Low Impact Development: Ecological Solutions to Concrete Problems

Despite recent efforts to reduce carbon emissions and protect green spaces, the natural world continues to struggle as it attempts to cope with human development.

The climate is changing, oceans are becoming increasingly acidic, habitats – and the species native to them — are disappearing and, perhaps most importantly for Californians, our fresh water reserves are proving insufficient to satiate a thirsty metropolitan area.

Timescale of the Trouble

Solving these problems will not happen overnight. It is going to take decades of effort to undo the damage caused over the last century. This is an unfortunate fact, but it highlights an important lesson.

One of the best ways to solve a problem of tomorrow is to avoid it today. We can do little to change some of our existing problems, but we absolutely must make changes to the way we construct buildings, cars and cities, moving forward.

Fortunately, civil engineers, architects and city planners are beginning to understand this, and develop techniques and strategies that help reduce some of these problems.  Many of these new approaches specifically address the problem of storm water management, which is a common cause of many of California’s current challenges.

Low Impact Development

One of the best strategies for helping to clean up the environment is called Low Impact Development, or LID.

Low impact development is a storm management strategy that turns conventional storm water management methodology on its head. Whereas civil engineers historically sought to collect and channel runoff water, aiming to transport the water from the city to the ocean as quickly as possible, low impact development principles embrace a more effective solution that relies on the contributions of plants, trees and healthy soils.

LID strategies not only accomplish the targeted task – managing storm water more effectively — they do so without creating new ecological problems. In fact, LID strategies improve the health of the local environment in a variety of ways. They also help solve a number of tangential problems, such as reducing the amount of surface pollutants reaching the ocean.

Additionally, because LID strategies and techniques often emphasize the retention of natural areas, they help improve the aesthetics of most areas in which they are implemented.

Problems with the Current Paradigm

Hundreds of years ago, rain falling over Los Angeles – which was a more common occurrence than it is in these drought-stricken times — did not cause environmental problems. The ground absorbed what it could, while the rest followed the path of least resistance, and made its way to creeks and rivers.

Along the way, forests and wetlands absorbed much of this water, which kept the plants healthy and greatly reduced the rate at which rainwater flowed into the ocean. These vegetated areas also helped to store a significant portion of the runoff water, which reduced the number of erosion-related problems along the way, and reduced the amount of sediment and nutrients that reached the ocean.

By contrast, rain falling over modern-day LA often largely lands on impervious surfaces. Unable to absorb much – if any – water, the concrete and steel skeleton of our city carries the runoff away with devastating efficacy.

Confined to concrete channels and storm drains, the water cannot replenish the wetlands and forests as it once did. Instead, it leaves these habitats parched, causing stress for the plants and animals living within them. As these habitats dry out, the surrounding atmosphere dries out too, which often leads to reduced rainfall and exacerbates the extent and severity of droughts.

Low Impact Innovations

Low impact development principles solve most problems created by traditional approaches. Often, those engineering LID projects have stolen their strategies directly from the natural world. Like so many other good ideas, Mother Nature figured out this approach first.

The basic strategy is simple: Instead of channeling the water to the ocean like a high-speed train, slow it down as much as possible, and try to get rid of as much of it as you can along the way.

Fortunately, implementing LID principles is relatively easy. In a nutshell, you place an assortment of plants, trees and plenty of soil in the water’s path and let nature take its course.

Trees and plants not only absorb and store vast quantities of water, they also release water into the atmosphere as part of the process of transpiration. During these processes, the roots and microorganisms living in the soil filter out many harmful pathogens and pollutants.

By incorporating these “living sponges” into the design of cities, buildings and neighborhoods, the amount of runoff water exiting the compound is drastically reduced, and the local environment becomes cooler and more humid. Such areas require only modest maintenance, they are economically feasible to construct, and, they look great.

You can learn more about implementing low impact development principles in Los Angeles in this report (PDF), authored by Haan‐Fawn Chau, of the University of California, Los Angeles. Additionally, the United States Environmental Protection Agency has produced this fact sheet, which provides an overview of LID.