Design With Nature

Natural assets, such as forests, aquifers, waterways, and wetlands, provide valuable services to communities including, but not limited to drinking water, stormwater management, protection against extreme weather, maintaining air quality, and carbon sequestration. By incorporating natural asset management with overall asset management, local governments can assign value to natural assets, and understand nature’s important role in service delivery.

Natural assets, particularly wetlands and riparian areas, are essential for managing rainwater, protecting water quality, preventing floods, and conserving soil. By absorbing rain and snow, these natural assets recharge aquifers and slowly release stored water into watercourses. Natural assets filter pollutants and sediments out of surface water, buffer developed areas from flooding, and prevent soil erosion.

In nature, most rainwater is absorbed into the pervious soil where it is stored for use by plants and microorganisms, replenishes streams and recharges underground aquifers. During periods of heavy rain, streams and rivers handle excess flow. Urban areas, on the other hand, have large portions of impervious surfaces that do not allow water to be absorbed, and may have structures that constrain rivers from following natural flooding patterns. The conventional approach to managing stormwater is “grey” infrastructure, consisting of a network of curbs, gutters and underground piping systems designed to quickly convey rainwater away from urban areas. Typically the water is discharged into nearby watercourses, bringing with it pollutants and resulting in streambank erosion and damage to ecosystems. Green stormwater infrastructure (GSI) is an alternative to conventional pipe-and-convey “grey” infrastructure. GSI includes decentralized infrastructure that slows down water during heavy rain events and allows water

»Preserving water quality—natural wetlands in the lower Fraser Valley provide at least $230 million worth of waste-cleansing services each year, without taking into account the cost of replacing the wetlands with engineered infrastructure if they were lost

» Maintaining air quality—over the past 25 years, the Puget Sound region has lost 37 percent of its tree canopy and high vegetation. This lost tree cover would have removed approximately 35 million pounds of pollutants annually at a value of $95 million

» Managing rainwater—the lost tree cover in Puget Sound has resulted in a 29 percent increase in the rainwater runoff during peak events. Using reservoirs and engineered solutions to replace this lost rainwater would cost $2.4 billion ($2 per cubic foot)

» Reducing flood impacts—Canada’s wetlands provide flood control worth $2.7 billion annually. A Washington State study estimated the value of wetlands for flood control at $89,000 to $126,000 per hectare per year. Ten local governments in Massachusetts saved $90 million by protecting 3,400 hectares of wetland as a natural storage area for flood control. The cost was $10 million, compared with the $100 million it would have cost to construct dams and levees.

» Recharging aquifers—Many BC communities rely on groundwater for drinking water supplies.

Source: Olewiler, N. (2004), The Value of Natural Capital in Settled Areas of Canada. Published by Ducks Unlimited Canada and the Nature Conservancy of Canada