Although it looks old, the Lower Mainland is, geologically, young at heart. Its shape is ever-shifting, particularly after heavy rains.

For evidence of this, look no further than North Vancouver, where a 50,000-cubic-metre rockslide and debris torrent partially blocked a lower portion of the Seymour River last December, causing water to back up and pool in an area serviced by a steel-and-concrete structure long known as Twin Bridges. As of January, make that No Bridges.

During a recent tour with Mike Mayers, superintendent of the Lower Seymour Conservation Reserve (LSCR), the Straight saw firsthand the concrete abutments on both banks of the river, all that remains of the recently removed bridge deck, which was installed in 2009 as a replacement for its predecessor, a vital North Shore link for hikers and mountain bikers since 1926. (The first span to cross that part of the Seymour, completed in 1908, was taken down in 1992.)

“The river has risen about three metres to its new low flow,” Mayers said. “During rain events, we have seen the river level rise an additional seven metres in 24 hours.”

That much fluctuation, with uprooted tree trunks in the current forming a debris trap, forced the removal of the bridge deck and steel support beams, which, Mayers said, will be repurposed elsewhere in the Seymour or adjacent Capilano watershed. (The LSCR offers a wealth of recreational possibilities but is part of the Greater Vancouver Water District and isn’t a Metro Vancouver park.)

Mayers was quick to rebut any suggestion that the rockslide had permanently dammed the river. “Although the river’s new low-water level isn’t receding at all, it’s mistakenly been called a lake or pond. Lakes don’t flow like this, so we don’t like to refer to it as such. If you come here during a rainstorm, there’s water over the former bridge’s abutments. Since the rock fall, there have been six such occurrences.”

Assessments of the long-term impact of the rockslide are under way for everything from fish migration to kayaking. Mayers said that many user groups, including trail runners, mountain bikers, and horseback riders, have been affected. “In terms of the overall impact, it’s less about specific activities than the general movement of people from east to west. The next- closest crossing is downstream at the Baden-Powell Trail, which is only a small footbridge on top of an old water main.”

Public meetings will be convened soon to gather opinions as to what new structure might replace the former bridge.

Care to see for yourself and enjoy a walk or mountain-bike ride along the newly improved Fisherman’s Trail? Head downhill from the LSCR’s Rice Lake gate along the 2.2-kilometre Twin Bridges Trail, which plunges into the narrow valley as Mount Seymour rises to the east. On foot, this should take 30 minutes; allow half that by bike on the descent but count on a heart-thumping pump back uphill should you choose to retrace your tracks.

Otherwise, from Twin Bridges, follow the wide Fisherman’s Trail as it leads north for almost seven kilometres to its junction with the paved recreational Seymour Valley Trailway—a magnet for road cyclists as well as experienced in-line skaters—which links the Rice Lake gate with the Seymour Falls Dam. Early on, keep a sharp eye out for an overgrown but still accessible narrow-gauge railway tunnel on the trail’s west side, one of the many remnants of the logging operations that cleared the valley of its original forest.

Near the conclusion of the Straight’s tour, Mayers proudly pointed out that the LSCR, at 5,668 hectares, is the largest green space in Metro Vancouver. Coupled with the adjacent Lynn Canyon Park and Lynn Headwaters Regional Park, that total rises to 10,535 hectares, the third-largest municipal green space in North America.

“I’ve been working here since 1989, yet I’m always amazed by its size,” he said. “If you walk off the trails, you’re immediately in dense bush. No wonder this place is a hub for film and television productions such as The 100 and Once Upon a Time. It’s out of this world.”

And with a few new wrinkles, it seems.

Access: The main entrance to the Lower Seymour Conservation Reserve is at the north end of Lillooet Road in North Vancouver. The entry gate is locked near dusk; there’s a small parking area just outside the gate for those who wish to explore without fear of being locked in for the night. It can also be reached by taking the #228 Lynn Valley bus from Lonsdale Quay and doing some walking. For info on current river conditions for kayaking, see the Liquid Lore website. More info on recreation is on the Metro Vancouver website.