Definition: An area (or plain) is a flooded area of land that is occupied by a river when it overflows its banks.

There are two types of flooding:

• Flooding in open water, which are caused exclusively by a significant increase in the amount of water in a river and not by a discharge in a given sector.
• The ice jam flooding, which are caused by an accumulation of ice or debris in a section of river to prevent the free flow of water and can create a back upstream.

The first knowledge on floodplains and Mapping Program

For several years, the Quebec government acquires and disseminates knowledge about flood zones. Following major floods occurred during the years 1974 and 1976 in several regions of Quebeak, the latter in conjunction with the federal government reached an agreement on policies to be adopted to reduce the damage caused by floods. This agreement called the Convention between the Government of Canada and the Government of Quebec on ??mapping and floodplain protection and sustainable development of water resources has led to the implementation of the mapping program. This program, which ran from 1976 to 2001, has achieved the official maps of flood zones on the territory of about 245 municipalities. More than 500 cards listing the risk of flooding were then produced, showing the extent of flooded areas by flood recurrence of 20 years and 100 years.