These data have been collected as part of Ministry of Forests research projects

BCFS Logo, small Coast Region Research Group

These data were collected by the Ministry of Forests and Range as part of hydrology research projects. The precipitation measurements were meant to quantify the amount of water available to contribute to runoff and therefore the timing of the occurrence may not coincide exactly with the precipitation event. In other words, snowfall events are recorded when the snow melts, not when it falls. Also, the rain gauges may not meet Environment Canada standards for wind protection or clearances form surrounding objects.

Chinukundl Creek, Queen Charlotte Islands 2000 to present

Lat 53 19 10 Long 131 58 20 Elevation 140 m

Gregory Creek, Queen Charlotte Islands 2003 to present

Lat 53 24 00 Long 132 26 50 Elevation 270 m

Nanaimo, Vancouver Island 1999 to present

Lat 49 12 06 Long 123 59 44 Elevation 120 m

Intensity, Duration, Frequency (IDF) “curves” illustrate how the quantity of rain varies with the length of the precipitation event and its return period. The return period is defined as the inverse of the probability of the event. For example, in Powell River, a storm that produces 13 mm of rain in an hour has a return period of 2 years which equates to a probability of 0.5 (i.e. ½ = 0.5). That is to say that a storm of this intensity is just as likely to happen each year as it is likely not to happen. A 12 hour storm with the same return period (2 years), on the other hand, has an intensity of only 3 mm/hr. In this case the intensity of the event must be multiplied by the duration in order to obtain the total rain that fell over the period (i.e. 3mm/hr _* 12 hr = 36mm).

IDF curves are commonly used, along with other data, in the design of drainage structures in order to ensure that they are capable of handling peak runoff events. The following links illustrate some of the IDF curves developed by Environment Canada for stations within the Coast Forest Region.