Open main menu

LID SWM Planning and Design Guide β

Notation

Revision as of 15:30, 4 October 2017 by Jenny Hill (talk | contribs)
Ac
Area of the catchment, whole contributing drainage area (usually in m2).
Ap
Area of the practice e.g. footprint area of a bioretention cell (usually in m2)
d
Depth e.g. of an infiltration practice (units of length, usually m)
L
Length, e.g. of a reach, channel or swale (usually in m)
m
run of side slopes in channel cross sections (length, but usually expressed as a ratio in relation to rise. e.g. side slopes = 1:3, so m = 3)
n
Manning's coefficient (unitless) (Note: for clarity porosity is being expressed as 'void ratio' and sharing the notation VR
q
infiltration rate in (length per time, usually mm/hr) (before or after application of safety factor?)
Qp
Peak flow in units of volume per time (e.g. m3/s)
R
Ratio of catchment (Ac) to the practice footprint area (Ap). syn. I/P ratio. Forgreen roofs (and often permeable paving systems) this will be 1:1. In bioretention it may be 15 or 20 to 1.
Ra
Existing rise of swale gradient (length, usually m)
Rb
Rise of compensation gradient for an enhanced swale (length, usually m)
RVCT
Runoff volume control target (as outlined by MOECC, units are mm)
S
Longitudinal slope (m/m, i.e. dimensionless)
SCF
Safety correction factor (dimensionless)
t
time (usually in hrs)
VR
Void ratio, as usually applied to aggregates and yard materials. In this guide, it is also applied to native soils in lieu of porosity (unit for both are vol/vol, i.e. dimensionless)
y
Depth of water (length, usually m or sometimes mm)