Watershed Wise Landscape Architecture
This front yard incorporates several watershed wise features. The down spouts direct rain water from the roof into depressions in the landscape called swales or infiltrations basins. Gaps filled with pebbles are installed between the concrete steps and pavers so that water drains into the garden not running into the street.
The development of buildings, houses, roads, and communities alters the course water takes through our landscapes. This profoundly impacts watersheds everywhere, polluting oceans, causing flooding, depleting aquafers, troubling fish populations, and causes heat islands that exacerbate the problem by driving away the rain.
It’s a sad situation, but the solutions are simple. If we viewed every property we developed as a mini watershed, and we recognized each site in relation to the part it plays in its watershed, we would be well on our way to mitigating the issues described above.
In nature, when rain falls or snow melts, gravity draws water downhill, creating creeks and streams and eventually flowing into larger bodies of water, including lakes, bays, and oceans. Along the way, water is slowed and absorbed in minor depressions in the soil. Plants then receive the water they need to thrive—creating forage and habitat for local fauna and modulate temperature—increasing the chances of future rainfall. Soil and plant roots also filter water, replenishing aquifers and waterways with clean water. If we consider our built environment as an element of the watershed, we can live in harmony with natural processes.
The Los Angles river was paved creating a conveyance of polluted water from the streets straight to the ocean. Today parts of the river have been opened up and restored to living breathing ecosystems. Now plants and soil have an opportunity to clean the water before it overwhelms the ocean. Trees and plant life flourish working to cool the city and clean its air and thirsty birds, insects and aquatic creatures have a place to frolic.
Directing rainwater from gutters, roads, and parking lots into depressions in the landscape is crucial to integrate the built world with the natural world and its watershed systems. When these depressions are planted with the right plants, cooling lushness can be achieved with minimal additional irrigation. Permeable hardscapes are also an important method for slowing and sinking rainwater: large slabs of concrete or grouted flagstone should be avoided and replaced by gravel pathways, decking, and plantings or gravel installed between smaller sections of concrete and flagstone, allowing for space for water to sink into the ground.
Curb cuts were installed in this parking lot in Carpinteria, California. Oil and asbestos from cars accumulate with smog particles and fecal matter from neighbor hood pets all flow into these planters where soil microbes can break down these pathogens before they drain into the ocean. The added benefit is that these plants (specifically chosen to thrive in these conditions) work to cool the parking lot without requiring a lot of supplemental irrigation
Water is a prerequisite for life. Designing the built world with natural processes in mind creates more resilient and sustainable communities, thriving watersheds, and the opportunity to live in harmony with nature.