After being recruited to do a physical watershed assessment by the Sunshine Coast Community Forest (SCCF), geo-engineer Glynnis Horel made a number of recommendations to help mitigate the impacts of forestry and development on Wilson Creek.
“The primary concerns for management are maintaining adequate riparian buffers, wind-throw management and sediment control,” she explained at a public meeting on Monday, Aug. 27, at the Seaside Centre in Sechelt.
Horel was recruited after a community forest sub-committee requested information on the health and status of the Wilson Creek watershed.
Logging in the area was put on hold and, according to SCCF chair Glen Bonderud, that resulted in a direct loss of about $182,000.
“If we were a publicly traded company, I think there would have been a shareholder revolt,” he said.
According to SCCF operations manager Dave Lasser, the geo-engineer was chosen for her experience, having conducted dozens of similar coastal watershed assessments.
“It was a short list of people,” Lasser said. “Over the course of her career, she’s worked for government, she’s worked mostly as a consultant, she’s done over two million hectares of watershed assessment on coastal B.C. She’s widely experienced.”
Horel’s work was aided by the use of laser-guided topography or LiDAR.
Compared to older methods, the researcher was able to map the elevations in the watershed to a one-metre accuracy. The result was a detailed topographical map that could include much smaller streams for analysis.
LiDAR “basically peels off vegetation and allows us to look at ground surface conditions,” she said. “We can see how subtle the changes in topography are.”
Her model described the watershed as an area that experiences an extreme year-to-year variation in peak flows, something typical of Coastal models. She described the Wilson Creek watershed as a ‘mosaic’ of areas that have been variously impacted by human influences.
In the lower watershed, the impacts of development have played a significant role in causing alteration.
Roads, flat surfaces, removed trees, ditches and other types of developments have shifted the way water navigates the watershed, as well as the sediments it picks up along the way.
Where forestry is concerned, the removal of canopies increases the impact minor rains or snow events have on stream flows, which are forced to directly absorb water that might have simply evaporated. As young trees grow, they recover this ability to ward off light rains and hold snow.
“If you remove the canopy, that goes to run-off,” she explained.
She called for sediment control around managed forest lands, pointing specifically to the road system and gully sidewalls.
Gully sidewalls are the most significant source of sediment entering the waterways, she said.
“I’ve recommended the Community Forest do wind-throw assessments wherever cutblocks border streams or gullies, in order to avoid compromising riparian function,” she said.
For example, disused forest service roads and recreational pathways, especially on steep inclines, can feed streams and creeks with a steady dose of sediment.
Root networks and wood debris also play a vital role in the prevention of erosion.
The engineer stressed the need for a professional assessment before logs and other debris are removed from streams and creeks, in order to avoid these damaging effects. Not only do they prevent erosion, she said, but they’re important for the maintenance of the structure of the waterways through their management of water flows.
Lakes and small bodies of water can also play an important role in buffering stream flows, something Wilson Creek lacks. Small ponds along Houston Creek, she said, are thus likely quite important for sustaining summertime stream flows in that area.
“Probably the biggest concerns with stream flows in the Wilson are likely to be low flows, not peak flows,” she argued. “The absence of water storage in Wilson Creek suggests to me that for water extraction and fish, low flows are likely to be the critical problem.”
Other recommendations from Horel included the use of wet weather guidelines, specifically policy and practice to avoid sediment from entering waterways during storm events. To this she added the need for terrain stability assessments and a management model that would help address the effects of wind, sediment and vegetation loss along streams.
With regards to managing the forest, Horel said the focus should be on the age and distribution of trees, in addition to cut allowances.
“We sometimes see direct conflicts between what is needed for infrastructure and what the stream needs for its health and habitat,” she said.