Currently, floodplain management is based on a single variable: the probability of a flood occurring that would lead to flooding of the area. This is the well-known 0–20 years / 0–100 years approach, which has been used in Quebec for many years.
On the other hand, a risk-based approach to flood management involves taking into account not only the probability of flood occurrence but all factors affecting the risk level. Characterization of these factors is necessary to measure the level of risk and identify options to reduce it.
The MMC would therefore like to implement a risk-based approach throughout the area under its jurisdiction. This approach is internationally recognized by flood experts, including the French organization Cerema.
The following are the main steps involved in measuring flood risk level: First, characterization of the probability of flooding is calculated based on the flood hazard and the effectiveness of preventive and protective measures. Vulnerability, defined as the susceptibility to damage, is then characterized. Vulnerability is determined by the significance and nature of the elements that are exposed to flooding and their degree of exposure. A flood risk assessment matrix is used in this step. Lastly, actions to reduce the probability of flooding and/or the vulnerability of the exposed environment are developed.