Sustainability and Development
When forested land is logged and changed to pasture or is developed for other uses, less rainfall is caught and retained by the trees and soil. More runs off the land, increasing the flow in downstream ditches, creeks and streams. With “intense” development, more land is covered with impervious surfaces such as asphalt or roofs, dramatically increasing runoff. The increase will, if not managed, result in the erosion of creek banks and downstream lands will be flooded.
The City of Abbotsford requires stormwater management measures for urban development.
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Runoff Water Quality
Rainfall which runs off the land in the City is collected by ditches in the rural areas, and by roof drains, catch basins, lawn drains, and some ditches in the urban area. It is conveyed by ditches or underground pipes to nearby watercourses. The quality of the flow in the runoff is adversely impacted by human-generated pollutants from both urban and rural activities.
Protection of the City’s fisheries sensitive watercourses is an important environmental objective. Recent advances in ways to improve the quality of urban runoff are being reviewed and added to the City’s development requirements. As new infrastructure is built, water quality devices are added to screen out some of the pollutants.
For infrastructure that is already built, City activities such as street sweeping and catch basin cleaning help keep pollutants out of downstream creeks and streams. But, there is definitely a role each resident can play, by:
- minimizing herbicide and pesticide use on lawn and garden areas;
- washing cars on lawn areas, not on driveways and roads;
- recycling used oils and antifreeze, and not dumping them in catch-basins; and
- keeping topsoil deliveries off the street
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In urban areas, surface runoff is generally directed to detention facilities and released slowly into underground storm sewer pipes, or infiltrated into the ground via infiltration facilities. The City of Abbotsford requires development of urban lands to be accompanied by stormwater management measures. Runoff from large roofed areas is encouraged to be infiltrated into the ground. Runoff from other areas is directed to large holding ponds or tanks, where it is released at a rate which attempts to mimic the pre-development runoff patterns. In some developments, management techniques such as rain gardens, biofiltration swales, and absorbent soils are or will be used to filter runoff (to remove pollutants) and to further reduce the peak flows.
The size of the underground pipes is calculated using criteria the City defines in the Engineering Standards of the Development Bylaw, but which is designed to protect property from nuisance flooding.
Those underground pipes are connected to creeks and streams, and the discharge has three main consequences:
- The quality of the water in the creek can be adversely impacted
- The volume of the discharge can result in downstream flooding
- The magnitude of the peak flow can result in downstream erosion
In older areas of Abbotsford, homes were often constructed without underground storm sewer pipes. In some locations, ditches convey the surface runoff away, in other locations, the soil is very porous, and surface runoff either does not exit, or it is collected and infiltrated into the ground using “rock pits” or other underground facilities. Home owners in these areas encountering drainage problems may need to check their perimeter drains, or re-construct their rock pits.
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Clayburn Creek Integrated Stormwater Management Plan (ISMP)
The City of Abbotsford completed an Integrated Stormwater Management Plan for the Clayburn Creek watershed. The watershed covers approximately 2,250 ha from mountainous area as high as 530 m to Matsqui lowland of 4 m above the sea level. It has multiple tributaries including Stoney Creek, Poignant Creek, and Diane Brook. Clayburn Creek drains through Matsqui Slough into Fraser River. The current issues include active stream bank erosion, instability of steep ravine slopes, and lowland flooding. In addition to the current residential areas, future development has been planned in the watershed.
The purpose of the study was to develop strategies to enhance flood and environmental protections while facilitating orderly development and redevelopment in the upland area. The Final Report was adopted by Council in June 2012.
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