Rural Lowland Drainage & Irrigation
- Lowlands Irrigation Supply Update
- Rural Lowland Drainage & Irrigation in Abbotsford
- Freshet Seepage
- Ditch Maintenance Program
- Wind Erosion
- Fraser River Bank Erosion
Lowlands Irrigation Supply Update
Due to recent low precipitation in June and July, high temperature and low water level in the Fraser River, the irrigation water supply may be affected in the following areas:
- Sumas Prairie Lake Bottom - there is potential for low or no water supply toward the end of August; low tide levels are predicted for the last three weeks of August. The tide levels affect the Fraser River level, preventing staff from back flooding water into Sumas River, which is the main source for irrigation supply in Sumas Prairie; and
- Matsqui Prairie - no concerns for the irrigation water supply at this time.
The City will continue to update the status of the irrigation water. For further information, contact the City of Abbotsford Operations Yard at 604-853-5485 or firstname.lastname@example.org .
Rural Lowland Drainage & Irrigation in Abbotsford
Prime agricultural land, created by sediment deposited by the Fraser River, is located in the areas known as Sumas Prairie and Matsqui Prairie. Both areas used to flood regularly, and are now protected from further flooding by dykes. Drainage behind the dykes is improved by pumping water over them in winter/spring months, and irrigation water is supplied in ditches in summer months.
The funds needed to maintain and operate the improvements are collected from the benefiting properties via Local Service Area levies. A Dyking, Drainage, and Irrigation Committee, one for each area, makes recommendations to Council on the disbursement of those funds, and assists staff in the administration of the improvements.
The Operations division of the Engineering Department, managed by the Manager, Drainage is responsible for the operation and maintenance of the drainage and irrigation pump stations, and the flood protection dykes in the Sumas and Matsqui Prairie Dyking Districts.
For irrigation zones in each Prairie, please refer to the following:
During the summer months, snow on the mountain melts and the runoff causes the Fraser River level to rise. The Matsqui dykes are designed to prevent water in the Fraser River from entering into the Matsqui Prairie area; however, some water pooling in the prairie near the dyke may occur. This is quite common and happens around all dykes. This phenomenon is due to the pressure difference created by the high water level in the river. It is not dangerous as long as water coming out of the seepage pool* is clear. If, however, the water becomes cloudy or contains river sand, it is a sign of an active boil**. This is serious and needs to be addressed immediately.
To minimize the seepage pooling and/or a boil on you property, please avoid the following activities from May to September near the dykes.
- the removal of trees or stumps;
- deep cultivation of fields; and
- digging holes with machines.
Historical Seepage and Boil locations are shown below.
If you have experienced seepage and/or sand boils on your property and if you are in the process of selling, please provide this information to the potential buyer.
To report water pooling on your property or to get information on the freshet season, please contact the Dyking, Drainage and Irrigation Department at 604-853-5485.
*Seepage Pool: Clear water coming out of the ground on the land side of the dyke due to pressure from high water level in the river. This is very common and is not serious.
**Piping and Boil: When the water levels in the river stay high for an extended period of time, the seepage can increase in volume and velocity. This can, sometimes, start moving sand and soil from the dyke foundation. This erosion of sand and soil is called piping. The discharge end of the active sand or soil pipe is called boil. (Source: US Army Corps of Engineering)
Ditch Maintenance Program
The Ditch Maintenance Program is a service provided by the City to the agricultural and rural areas of Matsqui and Sumas Prairies. It includes cleaning approximately 280 km of ditches on an annual basis.
In 2012, changes were made to the Ditch Cleaning Pilot Program, in consultation with the DDI Committees and Department of Fisheries and Oceans.
The new Ditch Maintenance Program has worked well in the last few years. Minimal flooding complaints were received in both prairies. All ditch maintenance work was completed before November 30, ensuring the drainage system was ready for the rainy season. Please refer to the Ditch Maintenance Program Fact Sheet for more information on the Ditch Maintenance Program.
The ditch maintenance work is completed using a track excavator with a 3 meter wide ditching bucket. For the excavator to reach the ditches on or along your property, a clear 6 meter (20 foot) access next to the ditch is required.
Access for ditch maintenance was one of the major challenges we encountered since the new ditch cleaning program was in place. Access to some of the diches was restricted either due to crops, equipment or machinery.
To ensure the Ditch Maintenance Program is successful, it is important that clear access to the ditches on or along your property is maintained. If possible, please ensure:
- All crops and/or machinery are cleared from the land next to the ditches from September 15 to November 30 every year.
- All permanent crops such as blueberries, etc. be planted a minimum 6 meters (20 feet) away from the top of the ditch to allow clear access for cleaning.
Individual farmers will be notified to provide access at least two weeks before the excavator reaches their property.
Due to the limited cleaning window and the large number of ditches that require cleaning, if your ditch is missed due to unavailable access, staff may not be able to come back to clean your ditch. The ditch will be cleaned in the following year when access becomes available.
General information regarding ditch maintenance is provided below:
- Federal Fisheries Act and Watercourse Maintenance Factsheet - Ministry of Agriculture
- Fisheries Timing Window for Maintenance Work in Constructed Ditches Factsheet - Ministry of Agriculture
- Fish Salvage Factsheet - Ministry of Agriculture
A good Beneficial Management Practice (BMP) program will reduce soil erosion, air pollution and impacts on water quality. In the flat areas of Abbotsford, the north east wind in the winter months blows the soil from uncovered lands and fills in the drainage watercourses. This increases the need for ditch cleaning and increases the maintenance costs. Cover crops are an excellent way to reduce soil erosion. Please see below for guidelines to reduce wind erosion and information on the Beneficial Management Practices:
Fraser River Bank Erosion
Seven erosion arcs have formed along the south bank of the Fraser River between the northerly tip of Matsqui Prairie and Sumas Mountain since 1997. This section of river bank is prone to erosion and rock protection was placed along the bank in 1971 and 1983. Scouring along the south bank continues to be a significant problem. The river flow is changing direction causing scouring and deepening at the base of the bank. This eventually undermines the rock protection, causing the rock to move, resulting in bank erosion and movement. The erosion arcs visible above the water level are only the “tip of the iceberg” and most of the damage is occurring underneath the water level.
Erosion Arc E
Beharrell Road Erosion Arc (E) appeared on Metro Vancouver Parks lands (east of Beharrell Road) after the 2013 freshet and was only 30 m away from the Matsqui Dyke. If left unrepaired it posed a significant threat to public safety as it could undermine the dyke, flood Matsqui Prairie and result in potential loss of life and catastrophic economic impact. The Matsqui Dyke protects nearly 5,000 hectares of diverse agricultural land in the Matsqui Prairie, historic Clayburn and Matsqui Village, Matsqui First Nations and major regional infrastructure such as Highway 11, railways, National Defense Communication centre, BC Hydro towers, gas mains, water transmission main and the JAMES Wastewater Treatment Plant.
Design work for the Beharrell Road Erosion Arc was initiated in December 2013, with tendering and award in January 2014. Construction started in February 2014 and repair work substantially completed on March 31, 2014. Cost to repair the Beharrell Road Erosion Arc is $2.8M, of which $1.45M was funded by the Province and the remainder by the City of Abbotsford.
Erosion Arcs F and G
In December 2015, a sixth erosion arc (F) was discovered and was only 40 m away from the Matsqui dyke. The City engaged Northwest Hydraulic Consultants (NHC) to evaluate the latest erosion arc. NHC assessed the risk of the latest erosion arc and concluded that if left unrepaired, it would grow in size and potentially compromise the dyke during the 2016 freshet or sooner. In March 2016, Provincial funding of $4M was received to address the emergency repair. During the emergency repair work in April 2016, erosion arc F expanded downstream. The repair cost is now estimated at $3M, with some work remaining to be complete after the freshet.
Around the same time when erosion arc (F) was discovered, a seventh smaller erosion arc (G) was forming. New erosion arcs will continue to form along the south bank until a comprehensive approach is taken to deal with the change of flow within the river. The primary concern is that the erosion arcs will enlarge and eventually breach the Matsqui dyke causing failure and catastrophic flooding of the Matsqui floodplain which carries a significant risk of loss of life and an economic impact ranging from $1.8 Billion to $2.6 Billion.
The Fraser River Erosion Study, completed in July 2015 by NHC, identifies the cause of the erosion arcs to be sediment deposition in the main channel deflecting the Fraser River towards the south bank, which deepens the channel, causing the existing rock protection to fail, exposing the fine grained soils resulting in the formation of erosion arcs. The study identified six mitigation options with high level budgets to address this emerging concern.
In December 2015, Abbotsford City Council supported the “submerged rock spur” option, at a cost of $8 to $10M, and made a request to senior government funding to address this urgent issue. The rock spur option is the least disruptive option, can be done in phases, can be completed in sections to determine effectiveness, and is one of the less expensive options. (Note that the $8M does not include studies and environmental mitigation.)