Canada s exposure to flood risk. Who is affected, where are they located, and what is at stake

Transcription

1 Canada s exposure to flood risk Who is affected, where are they located, and what is at stake

2 Why a flood model for Canada? Catastrophic losses Insurance industry Federal government Average industry CAT losses jumped from a long-term average of $400M to $1B/year or more Government disaster spending experienced similar trends Government(s) leaning on industry for a solution, and to de-risk the Treasury s balance sheet 2

3 What insurers typically mean by flood? Fluvial (i.e., riverine or on-plain) flooding the capacity of watercourses is exceeded, leading to river overflow Pluvial (i.e., urban or off-plain) flooding surface and underground infrastructure in urban centres is unable to drain excess water flow generated by stormwater runoff (and/or snowmelt runoff), leading to overflow Coastal (i.e., storm surge) flooding the combined action of wind, waves and high tides, which may include tsunamis, along the coast of large bodies of water leads to overflow What insurers typically don t mean by flood? Sewer back-up excess water volumes overload a drainage system, leading wastewater to rise above basement drains and back-flowing into the home Seepage water from external and natural sources enters the home through cracks in foundations, basement walls, doors or windows Any other water damage such as burst pipes, leaking appliances, even if they lead to flooding of your basement. What insurance coverage is typically available? Water damage not caused by external, natural water sources (e.g., burst pipes, etc.) is typically bundled in the basic home insurance policy Sewer back-up widely available in the form of an additional endorsement to the basic home insurance policy Seepage available from some insurers in the form of an additional endorsement either bundled with, or in addition to, sewer back-up coverage Flood including both fluvial and pluvial flooding, is beginning to be available from some insurers, in select locations. Typically provided as an additional endorsement either bundled with, or in addition to, sewer back-up coverage * Insurance is a competitive marketplace and there is no standard product available or unequivocal common definition of covered perils. This slide outlines the definitions and coverage that are typically found in the marketplace. Actual coverage from individual insurers may vary. 3

4 Flood modelling methodology Input data Terrain elevation data: 30mt Digital Surface Model (DSM) complemented with best-available LiDAR data and bare-earth Digital Terrain Model (DTM) covering 100% of Canada s population Hydrometric data: Over 1.8M km of modelled river network using peak river flows from river gauging stations (Water Survey of Canada), estimated river flows for historical events, and 125,000+ modelled lakes and reservoirs Rainfall data: Intensity-Duration-Frequency (IDF) curves (Environment Canada) for 565 location, spatially interpolated to cover 100% of the territory Snowmelt data: Seasonal adjustment factors (Rainfall Frequency Atlas for Canada) used to account for the impact of snowmelt and frozen ground on water flows and surface runoff Land cover data: Land use, land cover, soil type, geology and vegetation data (Ecological Framework of Canada) used to account for surface roughness and losses due to infiltration Water and stormwater infrastructure data: Assumptions on infrastructure capacity and urban runoff coefficients used to account for urban subsurface drainage Flood defenses: Information on type of structure, size, location and standard of protection for flood defenses and flood alleviation schemes based on aerial images and local research 1. Hydrological modelling Use local hydrometric and climate data to estimate flows and rainfalls at different return periods (1/20, 1/50, 1/75, 1/100, 1/200, 1/500 and 1/1500 year) 2. Hydraulic modelling Full 2D modelling combined with 1D modelling (rural areas) to map defended and undefended flows for each return period, using edited elevation data (to remove structures/blockages) and accounting for losses based on land use, infiltration, and urban drainage 3. Flood mapping Output (separate and combined) fluvial and pluvial flood maps for each return period which - when overlaid with a full address, property and exposure database - can be used to quantify the exposure to flood risk for any location across Canada 4

5 Model outputs: flood hazard maps Fluvial Pluvial Combined Flood hazard maps are one of the key outputs generated by the model. They can be used to illustrate the extent of flood zones at different return periods In our model, flood hazard maps are available for seven return periods (between 1-in-20 and 1-in-1500 years) and can include fluvial flood, or pluvial flood, or both combined While they are frequently used for floodplain management and land use planning, flood hazard maps only describe the spatial extent of a physical phenomenon they are not a measure of risk Risk assessment requires the use of flood risk maps 5

6 From hazard maps to risk maps Property values and exposure data Demographic and socio-economic data Land and other geo-climatic data River and rainfall data Terrain elevation data Flood risk mapping: Information on the housing stock (e.g., type, age, value) and data on individual and household socioeconomic characteristics are then layered over the flood hazard data in order to move from a view of hazard to a view of risk, and identify not just where high-risk areas are located, but the social and financial impact of exposure to flood. Flood hazard mapping: Geo-spatial and climatic data is used to map out flood hazard extents i.e., which areas are affected by flood Basic Methodology Property catalog: Geocode and map out each residential property in Canada and its key attributes Frequency: Model flood extents at different return periods to determine how often each property is likely to get flooded Severity: Calculate the depth of water affecting each property and for each return period Exposure: Quantify the value at risk of each property at risk of flood Damage/Loss: Estimate annual average expected losses and total damage resulting from flood events 6

7 Live Demo 7