Sumas Prairie: Failed Dikes, Flooded Farmland: Flood Management

"The potential for flood losses grew rapidly during the last half of the 20th century in the lower Fraser Valley and estuary where the bulk of British Columbia's population, infrastructure, and flood-control structures are concentrated... Both federal and provincial governments slashed their professional capability in water management and flood control. The legacy was a costly system of dikes, financial disaster assistance and rapid encroachment on the floodplain. Most effort and funds were directed to compensation through flood loss programs run by well organized federal and provincial emergency measures organizations. This sequence of events was caused by a variety of institutional failures over more than 50 years. "

"...Most of the existing dikes do not meet current provincial standard, and would only provide protection against smaller flood events."

"The hydrology of the Fraser River Basin is dominated by snow accumulation and melt processes, leading to a prominent annual peak streamflow invariably occurring in May–July... some... have resulted in damaging floods in the region."

Various nonstructural adjustments to flood damage reduction are proposed for the Lower Fraser Valley including technical tools, policy objectives, policy instruments, policy paradigms, and best practices.

An Act for maintaining the safety and integrity of dikes while preventing detrimental effects on river processes and other parties.

There are more than 200 regulated dikes in B.C. with a total length of over 1100 kilometres, protecting 160,000 hectares of valuable land.

Climate change, pollution and waste management, biodiversity, sustainability and urban ecology.

Floodplain maps identify areas that experience periodic flooding from nearby rivers, lakes, streams and the sea and provide information on the spatial distribution of flood construction levels.

Creeks and streams, erosion and bank stabilization, maintenance programs, stormwater management and more.

The City’s drainage assets include approximately 500 km of gravity storm sewer and over 31,000 associated structures (manholes, headwalls, catch basins, etc.), 381 detention facilities, 526 km of ditches, 173 km of creeks, 1,296 culverts, 33 km of dykes, and 5 drainage pump stations.

"Overtopping is expected during Nooksack River overflow."

This report presents the work and results for modelling, flood damage assessment, flood mitigation analysis and benefit-cost analysis associated with flooding in the Sumas Prairie,... as part of the work for the Nooksack River Overflow Flood Mitigation Plan for the City of Abbotsford.

Fraser Basin Council Lower Fraser River 2D flood modelling and mapping, digital elevation model, flood risk assessment, seismic guidelines for dikes, orphan dikes, storm surge forecast model.

The Lower Mainland Flood Management Strategy (LMFMS) is aimed at reducing flood risk and improving the flood resilience of communities along BC's lower Fraser River and south coast — from Hope to Richmond and from Squamish to White Rock.

Fraser Basin Council one-dimensional hydraulic modelling on the lower Fraser River using MIKE11 software to generate an up-to-date design flood profile based on the following two scenarios:
• The estimated flow during the 1894 Fraser River flood combined with high spring tide conditions.
• The 200 year winter storm surge with high tide combined with a Fraser River winter flood.

The 74 dikes included in the assessment, as managed by 35 diking authorities, extend for over 500 km through the Lower Mainland, comprising about half of the total length of dikes in BC. Information regarding the dikes (regulated under the Dike Maintenance Act) is retained by MFLNRO and local diking authorities but has not been systematically analyzed with respect to their level of protection or organized into a readily accessible form.

A new initiative is underway to develop a Lower Mainland Flood Management Strategy to better protect communities along the lower Fraser River and coast – from Hope to Richmond and from Squamish to White Rock.

The main goal of the project was to develop an understanding of the most significant flood vulnerabilities in the Lower Mainland region and estimate the consequences of the selected flood scenarios, in terms of impacts and costs.

Links to Fraser Basin Council Lower Mainland Flood Maps.

The Lower Mainland has been exposed to significant flooding in the past, both by the Fraser River, smaller water courses and by high ocean levels, and is now largely protected by dikes that were built over a period of several decades to variable standards. BC Ministry of Forests, Lands and Natural Resource Operations (MFLNRO) retained Northwest Hydraulic Consultants Ltd. (NHC), assisted by Thurber Engineering Ltd. (TEL), to carry out an overview assessment of 74 dikes in the Lower Mainland to evaluate the level of protection provided by the dikes and to identify major deficiencies.

This report presents the work and results for modelling, flood damage assessment, flood mitigation assessment and benefit-cost analysis associated with flooding in the Sumas Prairie completed as part of the work for the Nooksack River Overflow Flood Mitigation Plan for the City of Abbotsford (City).

Datasets in the atlas have been organized under six main categories, including: base layers; communities; watercourses & wetlands; sensitive ecosystems; fish; and flood. A metadata database has been set up to capture the basic information about each included dataset and to make finding and working with particular instances of data easier.

To regulate the use of public and privately owned land adjacent to: Vedder Canal, Sumas Drainage Channel, Sumas River, and Marshall, Saar, and Arnold Creeks.

The new 2021-2026 Strategic Plan will guide the Fraser Basin Council in our work over the next five years. As we approach the close of our first 25 years of service, the plan also helps us keep an eye on the horizon to prepare for the next 25 years — which will bring sustainability challenges and opportunities.

A new independent report commissioned by Sierra Club BC looks at the relationship between forest management and severe climate impacts expected across B.C. It shows that governments can mitigate climate-related disasters like flooding, droughts, fires and heatwaves by swiftly reforming B.C.’s forestry practices, applying Indigenous knowledge to forest-related decisions, and protecting and restoring intact forests before the climate crisis worsens.