IT IS THEREFORE RESOLVED THAT the AUMA advocate for the Government of Alberta to revise the provincial standard from 1:100 to 1:200 for flood mitigation measures for all new development.
WHEREAS flooding is the most common cause of large losses impacting municipalities;
WHEREAS these community losses include social, economic, financial and the potential loss of life;
WHEREAS increasing frequencies of events are evident due to deforestation and climate changes;
WHEREAS current and detailed provincial flood mitigation and mapping is a crucial element of risk management to all Alberta municipalities;
WHEREAS the design flood mitigation and mapping is the design that is used to delineate the flood hazard area and is statistically created and based off the 1:100 year return period, 1% chance of occurring in any given year, calculated at the time of the mapping;
WHEREAS current and detailed flood mitigation mapping is required to support proper land use policies, infrastructure, transportation, flood warning, evacuation, and emergency management planning to prepare and respond to flooding;
WHEREAS the Province of Alberta has been promising the release of new flood mapping for the past five years;
WHEREAS it is important that standardized flood rules exist across the Province;
WHEREAS changing the design standards for flood mapping to a 1:200-year level, for new developments will significantly reduce projected losses; and
Floods affect both individuals and communities, and have social, economic, and environmental consequences. The consequences of floods, both negative and positive, vary greatly depending on the location and extent of flooding, and the vulnerability and value of the natural and constructed environments they affect.
Floods have large social consequences for communities and individuals. As most people are well aware, the immediate impacts of flooding include loss of human life, damage to property, destruction of crops, loss of livestock, and deterioration of health conditions owing to waterborne diseases. As communication links and infrastructure such as power plants, roads, and bridges are damaged and disrupted, some economic activities may come to a standstill, people may be forced to leave their homes, and normal life is disrupted.
Flood modelling establishes river elevations for a design flood. The flow rates and corresponding design elevations vary with the frequency of the event that is predicted to occur. More severe flood events (higher flow rates) occur less frequently than less severe events (lower flow rates). Historically the 1:100-year flow rate has been used as the design flood event in Alberta. The term 1:100 year means that there is a 1 in 100 (or 1%) chance of the modelled flow rate being met or exceeded in any given year. The 200-year event therefore has a 0.5% chance of occurring (or being exceeded) in any given year.
Changing the design requirement from a 1:100-year event to a 1:200-year event is more protective because it increases the area and corresponding elevations associated with flood hazard mapping. The amount of increase will depend on the topography and the river being modelled. This increase will result in a larger/higher “floodway” channel where typically no development can occur and a larger/higher flood fringe. Under current design requirements, flood proofing is required for flood fringe development up to the design flood elevation plus a buffer.
Generally speaking, by increasing the design requirement there will be a decrease in the chance of flood-related damage to new construction/communities during a high-water event. This increased standard is also more resistant to climatic shifts in the frequency and/of severity of flood events.
Better and more detailed flood mitigation and mapping is critical to generate data to determine communities’ risk areas, safe evacuation routes, and response planning. Better mapping can also inform municipal planning policies, infrastructure, transportation, and emergency management planning.
As these events have the potential for expanding in frequency and intensity, all municipalities must be provided with proper tools to mitigate impacts where possible.
This resolution aligns with AUMA’s past advocacy on flood mitigation, preparedness and emergency management. The resolution will be forwarded to the Government of Alberta for response and further advocacy will be recommended to AUMA’s Board by the Infrastructure and Energy Committee in the context of related priorities and positions.