Introduction to Low Impact Development

Low Impact Development (LID) is a concept in urban planning and environmental management that focuses on controlling stormwater and promoting sustainability in ways that are gentle on the environment. This approach uses natural processes and landscape features to manage stormwater runoff in urban and suburban settings. In a world where urbanization continues to grow, LID offers solutions that reduce the environmental footprint of cities, prevent flooding, and protect water resources. Let’s break down this idea, its components, and its benefits in a way that anyone, regardless of background, can understand.

What is Low Impact Development?

At its core, Low Impact Development (LID) is a design strategy that integrates environmental sustainability into land development. LID aims to manage stormwater where it falls, using techniques that imitate natural water cycles. Urban areas, particularly cities, are designed with lots of impervious surfaces like roads, roofs, and parking lots, which prevent rainwater from soaking into the ground. Instead, this rainwater flows into storm drains, often causing flooding, erosion, and pollution in local water bodies. Traditional systems rely on storm drains and pipes to direct water away quickly, but this can have negative consequences for the environment.

LID, on the other hand, uses methods that encourage water to infiltrate into the ground, evaporate, or be filtered naturally. The goal is to handle rainwater as close to its source as possible. Rather than using large, expensive systems to redirect water, LID techniques rely on simpler, more natural solutions that work within the landscape. By incorporating vegetation, porous surfaces, and other natural systems into development plans, LID minimizes the impact of rainwater runoff and helps maintain or restore the natural flow of water.

Why is Low Impact Development Important?

As cities grow and more land is developed for housing, businesses, roads, and other infrastructure, the amount of impervious surfaces increases. This leads to greater amounts of runoff when it rains, which can overwhelm traditional stormwater management systems. Without proper management, this water can carry pollutants like oil, trash, and chemicals into rivers and lakes, harming water quality and aquatic life. It can also lead to flooding, erosion, and the destruction of natural habitats.

Furthermore, traditional stormwater systems are costly to build and maintain. They often involve complex pipes, drainage systems, and large detention ponds, which can be expensive for municipalities to manage. LID offers a more sustainable, cost-effective alternative. It helps reduce the need for expensive infrastructure by using simple, nature-based techniques that can be integrated into existing development.

LID also has broader environmental benefits. It helps conserve natural resources, reduce the heat island effect (where urban areas become significantly hotter than surrounding rural areas), and improve biodiversity. Additionally, by mimicking natural systems, LID can create more pleasant and livable urban spaces with green areas, better air quality, and a healthier environment for people to enjoy.

Key Principles of Low Impact Development

• Preserve Natural Features: LID encourages preserving and integrating natural features such as wetlands, forests, and water bodies into development plans. This not only helps with stormwater management but also maintains the natural landscape, which can support biodiversity.
• Minimize Impervious Surfaces: The fewer impervious surfaces, like asphalt and concrete, the less rainwater runs off. LID emphasizes reducing the amount of these surfaces or replacing them with materials that allow water to soak through.
• Manage Stormwater Close to its Source: Instead of relying on centralized systems that direct water to large stormwater detention ponds or sewage treatment plants, LID seeks to manage water as close to where it falls. This approach can involve techniques like rain gardens, green roofs, and permeable pavements.
• Use Green Infrastructure: LID employs green infrastructure—landscape features such as vegetation, trees, and wetlands—to filter and absorb stormwater. These green systems work with the natural environment to improve water quality and reduce the need for artificial stormwater management systems.
• Promote Water Conservation: By capturing and using rainwater for irrigation, cooling, and other purposes, LID also promotes water conservation. This reduces the strain on freshwater resources and helps communities adapt to water shortages.

Key Techniques in Low Impact Development

Several key techniques are commonly used in LID. Each of these techniques works in a different way to reduce runoff, filter pollutants, and help water return to the earth naturally.

1. Rain Gardens: A rain garden is a landscaped area designed to capture and absorb stormwater. These gardens are usually planted with native plants that can tolerate both wet and dry conditions. They allow water to filter through the soil and be absorbed by the plants, reducing runoff and improving water quality.
2. Permeable Pavement: Traditional concrete and asphalt surfaces prevent water from soaking into the ground. Permeable pavement, on the other hand, allows water to pass through the surface and be absorbed into the soil below. This helps reduce the amount of runoff and prevents water from collecting on streets and parking lots.
3. Green Roofs: A green roof is a roof covered with vegetation. These roofs provide a place for rainwater to be absorbed, reducing runoff from buildings. Green roofs also help with temperature regulation, improve air quality, and provide habitat for birds and insects.
4. Rainwater Harvesting: Rainwater harvesting involves collecting and storing rainwater for later use. This can be done using barrels or more complex systems that funnel rainwater from roofs into storage tanks. The water can be used for irrigation, cleaning, or even indoor use, reducing the need for potable water and easing the strain on municipal water systems.
5. Bioswales: Bioswales are landscape features designed to channel and filter stormwater. They are often planted with grasses and other vegetation that help slow down the flow of water and allow it to soak into the soil.
6. Vegetated Swales: These are shallow, landscaped channels that direct water runoff into grassy or planted areas. These swales help filter water before it reaches storm drains and provide an opportunity for water to infiltrate the ground.
7. Tree Canopy Coverage: Trees play a vital role in stormwater management. Their roots help absorb water, and their canopies provide shade that slows down evaporation. Planting trees in urban areas is a simple yet effective way to improve water management and enhance the local environment.

Benefits of Low Impact Development

• Reduced Flooding: By managing stormwater where it falls, LID helps prevent water from overwhelming drainage systems, reducing the risk of flooding in cities and neighborhoods.
• Improved Water Quality: LID systems like rain gardens and bioswales filter out pollutants like oil, fertilizers, and pesticides from stormwater before it enters rivers, lakes, or streams. This helps protect water quality and supports aquatic ecosystems.
• Cost Savings: While some LID techniques may have initial installation costs, they are often less expensive than traditional stormwater management infrastructure. In the long run, they can also reduce maintenance costs and help municipalities avoid the costs associated with managing flood events.
• Environmental Benefits: LID reduces urban heat islands, improves air quality, and increases biodiversity by providing green spaces for wildlife. It helps restore natural hydrological processes, benefiting local ecosystems.
• Enhanced Community Well-Being: Green spaces, like rain gardens and tree canopies, provide aesthetic and recreational benefits. They improve the quality of life for residents, making cities more pleasant places to live and work.
• Climate Change Resilience: LID techniques help cities adapt to changing weather patterns by reducing the impacts of heavy rainfall and extreme weather events. By capturing and storing rainwater, these methods also make water use more sustainable in areas affected by drought.

Challenges of Low Impact Development

While LID offers many benefits, there are challenges to its widespread implementation. One major barrier is the initial cost of installing LID systems, although these costs are typically outweighed by the long-term savings. Another challenge is the need for proper maintenance, as LID systems such as rain gardens and permeable pavements require regular care to remain effective.

There can also be resistance to change, particularly in older cities or regions where traditional stormwater systems are deeply entrenched. LID requires a shift in thinking about how stormwater should be managed and a commitment to designing infrastructure that works in harmony with nature.

Summary

Low Impact Development is an innovative, sustainable approach to managing stormwater and creating more environmentally friendly urban spaces. By using natural processes, LID helps reduce runoff, improve water quality, and create greener, more livable cities. Although there are challenges to implementing LID, the long-term benefits for both the environment and communities make it a promising solution for the future of urban development. Whether it's through rain gardens, permeable pavements, or green roofs, LID represents a shift towards building cities that work in harmony with nature, making our environment healthier, more sustainable, and more resilient.