Q-2, r. 9.01 - Design code of a storm water management system eligible for a declaration of compliance

Section 79 Disposition versions

2020-12-31

79. In order not to increase the frequency of flooding of receiving lakes or watercourses and to not reduce the service level of infrastructures crossing the lakes or watercourses situated in the area of influence of the project, peak flows from the territory drained to a storm water management system must comply with the following conditions:

(1)  for the 10-year return period, the peak flow must be less or equal to the weakest of

(a)  the runoff peak flow prevailing before the carrying out of the work for the 10-year return period; and

(b)  the sum of the surfaces of the project multiplied by 10 L/s/ha;

(2)  for the 100-year return period, the peak flow must be less than or equal to the weakest of

(a)  the runoff peak flow prevailing before the carrying out of the work for the 100-year return period; and

(b)  the sum of the surfaces of the project multiplied by 30 L/s/ha.

For the purposes of hydrological calculations, the conditions prevailing before the carrying out of the work must be presumed to be a densely wooded area in good condition, unless photographs of the ground, aerial or satellite, show different ground occupancy, in a minimum continuous period of 10 years before the carrying out of the work. If more than one type of occupancy of the territory is present on the site during that period, the type of occupancy having the weakest runoff potential must be used for the calculations.

The service level of infrastructures is the annual probability that the hydraulic capacity of the infrastructures are exceeded and corresponds to the return period according to T = 1/P where T is the return period in years and P is the annual probability that the hydraulic capacity is exceeded at least once.

The influence area of the project is the section of the hydraulic section downstream of the project starting at the discharge point of the storm water management system and ending at the point where the area of the project represents only 10% of the watershed.

O.C. 871-2020, s. 79.

Not in force

In force: 2020-12-31

79. In order not to increase the frequency of flooding of receiving lakes or watercourses and to not reduce the service level of infrastructures crossing the lakes or watercourses situated in the area of influence of the project, peak flows from the territory drained to a storm water management system must comply with the following conditions:

(1)  for the 10-year return period, the peak flow must be less or equal to the weakest of

(a)  the runoff peak flow prevailing before the carrying out of the work for the 10-year return period; and

(b)  the sum of the surfaces of the project multiplied by 10 L/s/ha;

(2)  for the 100-year return period, the peak flow must be less than or equal to the weakest of

(a)  the runoff peak flow prevailing before the carrying out of the work for the 100-year return period; and

(b)  the sum of the surfaces of the project multiplied by 30 L/s/ha.

For the purposes of hydrological calculations, the conditions prevailing before the carrying out of the work must be presumed to be a densely wooded area in good condition, unless photographs of the ground, aerial or satellite, show different ground occupancy, in a minimum continuous period of 10 years before the carrying out of the work. If more than one type of occupancy of the territory is present on the site during that period, the type of occupancy having the weakest runoff potential must be used for the calculations.

The service level of infrastructures is the annual probability that the hydraulic capacity of the infrastructures are exceeded and corresponds to the return period according to T = 1/P where T is the return period in years and P is the annual probability that the hydraulic capacity is exceeded at least once.

The influence area of the project is the section of the hydraulic section downstream of the project starting at the discharge point of the storm water management system and ending at the point where the area of the project represents only 10% of the watershed.

O.C. 871-2020, s. 79.