In Search of a Risk-based Flood Policy in Canada: Will We Learn from Intense Floods?

Water News, Summer 2014 Edition

In the summer 2014 edition of Water News, Official Magazine of the Canadian Water Resources Association, Dave Murray (KWL Water Resources Sector Lead) and Lawrence Francois (Water Resources Engineer), explain current methods of flood prediction and floodplain management in Canada and their deficiencies in today’s context, lessons learned from recent intense floods, and discusses the benefits of a flood policy and framework with a risk-based approach that is consistent for effective floodplain management.

BREAKING THE HYDRO-ILLOGICAL CYCLE ON FLOODING

Many communities in Canada live within the clutches of hazardous conditions from mountainous watersheds, rivers and oceans.  Recent extreme flood events in Alberta have increased public awareness of flood risks.  The Disaster Financial Assistance Arrangement (DFAA) program established in 1970 provides federal tax dollars to Alberta in response to over $5 Billion in estimated flood damages, but does the DFAA encourage apathy rather than proper flood risk planning?  Canada lacks a uniform flood policy with incentives to create flood risk mitigation plans.  In addition, the lack of hydrology data limits flood professionals from accurately assessing future flood risk.  Yet the cost-benefit ratio for providing hydrometric and climate data is very positive, so spending to protect against floods looks clearly worthwhile.  A study for the BC Government (Azar, Sellars and Schroeter, MSRP 2003) showed a 19:1 cost-benefit ratio for providing hydrometric monitoring.  The CWRA community has been promoting effective water management for decades without breaking the “hydro-illogical” cycle.  Fortunately, recent interest from the insurance and real estate industries are pushing for flood mapping opening up an opportunity for progress

CURRENT METHODS OF FLOOD PREDICTION ARE OFTEN INADEQUATE

Traditional, water resources professionals quantify flooding to a specific provincial standard based on a frequency analysis of historical data from climate or hydrometric information and apply this to obtain flood hazards.  The “rear view mirror” method can be severely data limited.  For example, a 100 to 500 year (1% to 0.2% probability of exceedance) peak instantaneous flood may typically be predicted from 20 years or less of data.  While these methods are the industry norm, they often do not properly quantify the flood hazard.  The hydrology practitioner does not normally have the time or budget to do regional analysis or translation of potential storms into their study watershed to fully assess possible flooding impacts.  Also, there is often minimal information to allow understanding of geomorphology processes and their impact on flooding.  We have difficulty determining if recent severe floods are unprecedented or just severe events within the historical normal range.  Are our methods really the best we have to offer?

PROBABLE MAXIMUM LOSS

Probable Maximum Loss (PML) is generally defined as the value of the largest loss that could result from a disaster.  Using the Alberta flood damage estimate as an example, Public Safety Canada estimated $0.6-1 Billion in damages for a 500-year flood event (2007 dollars), yet we know that the current damage estimate is $5 Billion and rising for a 100-year event or less.  Projecting this unit cost to flooding estimates in the Public Works database for British Columbia, Alberta, Ontario and Quebec, would raise a combined flood damage estimate quickly to about $100 Billion.  For comparison, a 2013 earthquake study of British Columbia by Air Worldwide for the Insurance Bureau of Canada estimated $74 Billion PML for a Richter 9.0 earthquake.  The insurance industry generally would consider offering private flood insurance provided governments invest in quantifying flood risk and flood infrastructure, so that it can more accurately predict PML and set premiums based on underwriter estimates.

DO WE HAVE ENOUGH DATA, AND HOW MUCH IS ENOUGH?

The heart and soul of predicting flood hazards and then quantifying the risk is hydrometric, climatic, and topographic data.  Yet, governments have been systematically dismantled water data-gathering systems since the 1980s.  In British Columbia, the number of hydrometric stations has declined from about 800 in 1980 to 450 currently.  In the shale-gas-rich northeast of the province, private industry is providing water monitoring data to fill this void.

CAN A STANDARDS-APPROACH REALLY GET US THERE?

Flood standards vary across Canada, but in general governments have chosen a return-period standard, which provides guidance to the design or hydrology professional.  Frequency analysis allows quantification of the design event, and flood protection is most likely designed to protect to that standard.  If a flood is exceeded, then emergency flood funding is available for flood damage repairs.  This approach does not look at the residual risk of this standard being exceeded, the tolerable risk for a community, or the incremental cost to reduce the risk associated with the hazard and its consequences.

LIVING WITH RISK AND THE URGENT NEED FOR CONSISTENT POLICY

Planning policies and regulatory framework govern flood risk management.  There is lack of consistency among local governments in the approach adopted to address flood risk.  To reduce these inconsistencies, a tiered framework approach with minimum standards and requirements for flood assessment could be introduced at a higher level.  This would leave the detailed assessment of site specific problems to local governments.  Stakeholders input – including that from insurance and real estate industries – is essential in determining these policies.

FLOOD RISK MANAGEMENT FRAMEWORK

Flood risk management could become part of an ongoing and dynamic policy framework since the hazards and consequences change over time.  A phased risk management approach that relates and captures the changing risk conditions may be more appropriate over a standards based approach because it could more accurately reflect the actual risk and place the resources in the highest risk areas.

HAZARD VERSUS VULNERABILITY

Flood risk can be defined as a combination of hazard and vulnerability—a key element of risk.  The hazard, accounts for the probability of an event as well as its physical characteristics.  Vulnerability and resilience refer to the potential economic and social losses from flooding and capacity of the community to recover. In some cases it is essential to classify vulnerability, quantify the risk and determine possible damages in order to develop effective mitigation and land development strategies.

FLOOD HAZARD MAPPING AND RISK EVALUATION

Flood hazard maps provide excellent information for urban development and land use decisions.  They provide a technical basis for planning appropriate mitigation or adaptive measures.  Such maps can be used by stakeholders for existing and future development and allow for effective water management to take place.  Yet in Canada maps that do exist are decades out of date and many areas lack maps at all.  To plan and manage emergencies effectively, local governments have a responsibility to ensure that flood risk to properties and, in particular, their critical infrastructure is assessed accurately.

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