Re-vegetation reduces stormwater runoff in catchments through the interception of rainfall in the canopy, infiltration through root systems, and transpiration.
These re-vegetated areas can also function as filter strips to treat contaminants, slow overland flows, and attenuate stormwater quantities. There is a suite of environmental services provided by vegetation within a catchment, including enhancing biodiversity and ecosystem values, landscape amenity, dust interception, and temperature moderation.
Trees in particular have several advantages over other vegetation in improving water quality. They uptake nutrients, stabilise banks and steep slopes, transpire significant water volumes, and contribute carbon as fallen material that aids in denitrification processes in soils. Trees also provide a shaded environment that slows the establishment of weed species and reduces stormwater runoff temperatures.
The effectiveness of vegetation for stormwater quality treatment is dependent on the organic content and structural diversity of associated soils, and the relative proximity of root systems to groundwater. Fungi and microbes, abundant in healthy soils, aid in the translocation of nutrients to plants, and store other contaminants in inert forms. The organic layer of soil also intercepts and attenuates large volumes of stormwater, aiding in infiltration to subsoils. A mature forest can absorb up to 14 times the water of an equivalent grass area (Shaver, 2010a).