J. Hillaby , H. Englund and E. Gruhs
The “Dillabough Grind”
Background
We are a fortunate crew to have the knowledge and history available to us from such people as Ernie Gruhs, Leonard Teppema and the late Bruce McLeod. Each has indicated that Dillabough Creek is of special interest to them, and have gone to some length to encourage like-minded people to share that interest. On Thursday, 3 of us (4 including Leonard) did just that.
Our specific objective was to locate the Dillabough Creek falls and document their location and configuration. In particular, we needed to identify whether or not these falls were an impassable barrier to upstream migrating fish, for adult salmon in particular. To do this, the falls must be viewed from the bottom and yup, you have to crawl down into the canyon below.
Take home messages
We are grateful to Leonard Teppema for showing us around and facilitating access to the top of the falls; however, getting to the top was considerably easier than getting to the bottom. Those of us that have done the “Grouse Grind” can report that North Vancouver has nothing on Horsefly.
The falls consist of one 15 to 20 metre vertical rock face with a trickle of water coming over the top. There is a plunge pool at the rock bottom with a wetted depth of about 3 inches. In natural saystems, most fish migration barriers are partial ones – either they are temporary, some fish get over at different water levels, or it works for some sizes/species and not others, the stream channel eventually carves around it, etc. In this case it is clear that no fish will be getting up this barrier, and most wouldn’t survive the trip down. It is a permanent geological feature of the stream channel, and stands by itself.
Note that at the base of the falls on Dillabough Creek we measured 8.62 pH (neutral is 7), -80 ORP (some pollutants will not be easily reduced), water temperature comfortably cold at 11.2 – 11.5 oC, dissolved oxygen at 91% saturation and conductivity fairly well ionized at 192 microsiemens/second. A word about pH and ORP (oxydation-reduction potential). These readings reflect the landscape ecology of the watershed – while we can change the water chemistry and alter these numbers in an aquarium or a water treatment plant, in a natural system they are what they are.
The soils are fascinating. Leonard showed us the soil profile from a dugout in the hayfield well up the slope from the creek, showing several feet of peat moss, old snail shells and a high water table, indicating a historic lake that has gradually filled in. Perhaps there is a soils scientist out there that can contribute to our knowledge?
What’s next?
Due to technical difficulties, we were not able to document the location of the falls (in terms of GPS coordinates) or provide an upstream-facing photo. We’ll go in again and correct that, but not right away.
Next week – Dillabough Creek upper and lower sites, for water quality and channel comparisons. September 16th, be outside SAWS at 1 pm.