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New gov't guidelines to help with flood planning

Delta's location on floodplain puts the community at risk of flooding, some areas of dike in need of upgrades

Delta's engineering department will be taking a close look at newly released maps and guidelines from the province on areas vulnerable to flooding by 2100.

The report, Coastal Floodplain Mapping Guidelines and Specifications, recommends standards for topographic mapping and identifies engineering requirements for establishing building elevations in coastal areas, a government news release says.

It also includes a sample floodplain map showing potential floodplain areas to the year 2100, along with an engineering design brief.

The information is to help urban planners and local government officials incorporate rising sea levels into flood-hazard area landdevelopment decisions, such as official community plans, zoning, subdivisions and building permits.

The new guidelines complement a report released last May on how rising sea levels will affect coastal B.C. over the next cen-tury, titled Climate Change Adaptation Guidelines for Sea Dikes and Coastal Flood Hazard Land Use.

Rising sea levels could cause flooding in Metro Vancouver communities that never had to deal with it before. Areas such as Richmond and Delta that are already below sea level and have sophisticated systems of dikes, large drainage ditches and pump stations. There's about 61 kilometres worth of dikes and seawalls in Delta.

Delta's location on the Fraser River floodplain puts the community at risk of flooding, according to the municipality. The main flood threat for Delta occurs from winter storms and then along the Fraser River in the late spring and early summer, particularly when there's a heavy snowpack and a sudden spell of hot weather following a cool spring. The area's two major floods, in 1894 and 1948, were both a result of this spring freshet.

The government report last May noted Delta has a high risk and consequences of flooding, while the adaptation options could include protecting or accommodating, or retreating by allowing no new development or redevelopment.

Today, Delta's dike system is constructed to what's described as a 200-year flood level, which means the risk of flooding is estimated to be 0.5 per cent in a given year. There is a 99.5 per cent chance that flooding from high water will not occur.

However, what's not clear is how the current dike system will hold up with rising sea levels due to climate change by 2100.

The engineering department will review the government projections and report back to council, said Delta engineering director Steven Lan,

Noting several dike improvements have been undertaken in the Boundary Bay area and East Ladner, Lan described Delta's diking system as "robust" but there's areas identified for upgrades.

A 2007 Delta engineering report noted that a breach of the diking system would result in the ocean flowing several kilometres inland.

At the Federation of Canadian Municipalities conference in June, a motion by Delta was endorsed calling on the senior governments to work together to develop a funding program to assist coastal communities with flood protection, as global warming poses a serious threat to Lower Mainland communities, many of which are faced with the risk of inland flooding and coastal sea level rise. The submission by Delta notes, "Local governments in the Lower Mainland have limited economic resources. Many do not have the financial capacity to fund large-scale adaption projects. For seaside communities, these types of adaption projects will involve dike/seawall upgrades, improvements to foreshore protection, and land use planning and food level policy changes."

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