The Chilliwack River watershed lies within the upper Fraser Valley about 100 km E of Vancouver. This large watershed has an area of ~1,230 km2. The City of Chilliwack is located within its lower reaches where dyked floodplain, referred to as the Fraser Lowland, has created suitable terrain for development. Below Vedder Crossing the Chilliwack River changes its name to Vedder River and then to Vedder Canal which flows mainly N to drain ultimately to the mighty Fraser River. The watershed lies mainly within the Fraser Valley Regional District (FVRD) but a portion does lie within the City of Chilliwack and a very small portion within the City of Abbotsford. This is based on the consideration that the Vedder Canal and it’s tributaries are part of the watershed.
Up slope, the terrain of the watershed changes to low lying – moderate elevation ridges and mountains (Skagit Range) supporting fast flowing tributary creeks, lakes and the Chilliwack River. Continuing E, the Skagit Range mountains continue to elevate and increase in steepness. The grade of the Chilliwack River does increase through this region, but only moderately overall, and then meets with its large natural reservoir, Chilliwack Lake. More than 50% of the watershed is >1,500 m elevation.
Upstream from Chilliwack Lake, the Chilliwack River continues more like a relatively large, slow moving creek to cross the Canada-USA border. Further afield within the very headwaters of the upper Chilliwack River, drainage is made from the steep slopes of the North Cascade Mountains within Washington State. Approximately ~1/3 of the watershed lies with the U.S.A. Along its length at least 16 major tributary creeks branch off from the Chilliwack River, several of which lead through significant, low side valleys.
TOPOGRAPHY OF THE CHILLIWACK RIVER VALLEY
The Chilliwack River drainage exhibits an extremely diverse topography. The W portion of the drainage at the Fraser Lowlands lies at near sea level. Sumas Prairie was once part of Sumas Lake which was drained in the 1920’s – this area is slightly above sea level. Likewise, other lowland areas currently being farmed in the Chilliwack region are just above sea level.
Nearby, Cultus Lake sits at ~40m elevation. The U-shaped valley bottom gradually increases in elevation from here to the E. Chilliwack Lake rests at ~600m elevation. The upper Chilliwack River, within the valley bottom, continues its gradual incline to the S across the Canada-USA border. The main valley connects to several V-shaped creek valleys which hold the many tributaries of the Chilliwack River. Many of these side valleys are very steep walled.
The mountaintop elevations increase from ~928m at Vedder Peak in the W to several peaks between 2,000 – 2,400m in the E surrounding Chilliwack Lake. The highest mountains within the drainage (in Canada) are Slesse Mtn and Welch Peak, both very close to 2,440m elevation. The majority of these mountains are very steep sided with high ridges being common, which connect to surrounding peaks.
MOUNTAINS OF THE SKAGIT RANGE
The Skagit Range Mountains are a sub-range of the Canadian Cascade Mountains. This range is bordered by the Silverhope Ck and Skagit River drainages to the E (Hozameen Range), the Fraser River to the N and the Canada-USA border to the S. The Skagit Range includes significant named ridges and groups of mountains including Cheam Ridge, Illusion Group and Rexford Group – all of these are popular mountaineering destinations. Typically, steep trails ascend the lower reaches of these to access the alpine where talus/scree must be overcome to access the cherished scrambling and mountaineering routes above. The word ‘skagit’ is taken from the name of a Coastal Salish Indian band living along the Skagit River.
Cheam Ridge consists of several high peaks from N to S: Cheam Peak, Lady Peak, Knight Peak, Baby Munday Peak, Stewart Peak, The Still, Welch Peak, Foley Peak and Conway Peak. Elevations of these peaks range from ~2,100 – 2,440m. Remnants of several alpine glaciers exist such as Stewart Glacier, Wahleach Glacier, Foley Glacier although it appears that these glaciers are receding. A few picturesque tarns and small lakes can be found in the alpine along the ridge such as ‘Spoon Lake’ and Williamson Lake. Mountaineering (climbs and scrambles) is commonplace here while the mountains at either end (Cheam Peak and Conway Peak) have trails which extend not far from the summits. The ‘Lucky Four Group’ has been used to describe the following four peaks: Foley Peak, Welch Peak, Stewart Peak and Knight Peak. The word ‘Cheam’ comes from the name originally given to Cheam Slough. ‘Cheam’ was taken from the local native word meaning ‘wild strawberry place’. It is speculated that the ‘Lady’ in Lady Peak was Ms. Phyllis Munday, an accomplished mountaineer and acquaintance of A.S. Williamson, superintendent of the Lucky Four Mine. Phyllis Munday and her husband, Don, were the first to summit several summits around SW BC and the BC coast mountains including Mt. Foley in 1924. Mt. Conway is named for RC Leading Seaman Archibald H.W. Conway of Chilliwack, who died at sea in 1940 during WWII.
The Illusion Group and Rexford Group mountains border one another and together, compose the divide between the Nesakwatch Ck and Centre Ck drainages. These mountains are characterized by towering, steep walled, granitic peaks giving rise to the adage ‘the poor man’s Yosemite’. Most of these spectacular peaks range from ~2,000-2,329m elevation. Scree typically collects as the base of the peaks here. This area is noted for numerous climbs and a few good scrambles.
Slesse Mtn. is perhaps the most well known mountain within the Skagit Range. Together with its nearby ‘Slesse Mtn. – S Peak’, these dark multi-horns make for a well recognized landmark from afar. These peaks sit atop the divide between Slesse Ck and Nesakwatch Ck drainages which also encompasses Mt. Parkes, Crossover Peak, Mt. MacFarlane and Mt. Pierce. Slesse Mtn. provides some world class climbing routes up its flanks. Some relatively small glaciers exist on Slesse’s E side, some of which are hanging glaciers known to release broken ice from time to time. Altogether this divide offers a variety of excellent climbs, scrambles and hikes. The name was originally pronounced as ‘suh-lee-see’ from the Coastal Salish word meaning ‘fang’. Mt. Pierce is named for prospector G.O. Pierce who developed a gold property at ~1,500m elevation near the turn of the century. Reports indicate that gold ore was produced here.
The ‘Border Peaks’ consisting of Canadian Border Peak, American Border Peak as well as Mt. Larrabee and The Pleiades all reside along the same divide between the Tamihi, Borden and Slesse drainages. The Canada-USA border dissects this ridge between the Canadian Border Peak and the American Border Peak. The main activity here is mountaineering although some good hiking can be found along the ridge which extends to the W as ‘Spencer Ridge’. The N side of ‘Border Peaks’ ridge is well glaciated although these glaciers are receding. All summits within the USA are officially outside of the Skagit Range.
Other popular mountains and ridges for hiking or mountaineering include (from W to E):
Vedder Peak – a low, forested, ridge-like summit overlooking Cultus Lake. This mountain is the only mountain (Vedder Mtn.) having a summit with a different name.
International Ridge – an undulating, forested ridge with a trail along its length to its S end marked by Mt. Amadis.
Mt. Tom – by far the lowest elevation mountain on this list and the closest to development. Nonetheless, a nice location for a walk or short hike.
Ford Mtn. – this mountain is more of a forested ridge which extends to Williams Peak and was once used as a fire lookout.
Mt. Thurston – another ridge-like summit with meadows which extends E to include Mt. Thurston and Mt. Mercer. Mt. Mercer is named for Canadian soldier, W.R. Mercer of Rosedale, who died in battle in 1945 (during WWII).
Mt. Laughington – a lone, ridge-like, minor summit connecting to Cheam Ridge.
Mt. Archibald – a minor summit, dotted with outcrop, which is connected to Cheam Peak by a long ridge. This mountain is named for RAF Flying Officer R.E Archibald of Rosedale, who died in battle in 1942 during WWII.
Williams Peak – an impressive, prominent horn situated at the E end of the ridge which extends W to Ford Mtn.
Mt. McGuire – a prominent, light colored summit composed mainly of limestone in the upper reaches. The karst-like topography along its shoulders is known to contain at least one cave system.
‘Flora Peak’ – this somewhat rotund summit is one of the high points along the long and mostly forested ridge between ‘The Gargoyles’ and Paleface Mtn. (or Mt. Moroniuk).
Mt. MacFarlane – a high point along a magnificent caldera-like rim which includes Mt. Pierce. ‘Upper Pierce Lake’ is a jewel which fills the crater-like depression, likely an ancient cirque basin.
MacDonald Peak – an irregular shaped peak along a sinuous ridge connecting Mt. Webb to Mt. Lindeman. Blocky, broken rock predominates. Mt. Webb is named for Christopher Webb, a federal government engineer and later a BC Electric Co. employee, who first visited the area in 1916 while searching for the headwaters of the Chilliwack River to determine if a potential source of hydro-electric power existed here. He built a log house near the N end of Chilliwack Lake in 1929 which is still in use today by his descendants.
Other less popular mountains and ridges which present alternative and worthwhile destinations for mountaineers are:
Mt. Northgraves – a massive multi-summit peak along the Foley Ck – Chilliwack River divide.
Goetz Peak (pronounced ‘Gertz Peak’) – a high point along the rocky, undulating ridgeline between Mt. Northgraves and Williams Peak.
‘Goat Mtn.’ – a long and relatively rounded ridge and summit connecting to the Mt. Northgraves – Williams Peak ridge. Aka ‘Porcupine Peak’.
Mt. Wittenberg – the high point along a relatively even ridge which connects to the ‘Flora Peak’ – Paleface Mtn. ridge.
Mt. Meroniuk – an irregular shaped summit connected to nearby Paleface Mtn.,which overlooks Chilliwack Lake. Mt. Meroniuk is named for Canadian soldier G.H. Meroniuk of Agassiz who died in battle in 1944 (during WWII).
Custer Ridge – a long partially wooded ridge extending from ‘Paleface Pass’ to Thompson Peak. Contains steep sided Klesilkwa Mtn. and a few minor summits.
‘Liumchen Ridge’ and Liumchen Mtn. – This long, snaking, partially forested ridge includes ‘Windy Peak’, ‘Old Baldy’, Church Mtn. and terminates at its S end at Liumchen Mtn., located right along the Canada-US border.
Mt. Parkes – a well known mountaineering route traverses the Slesse Mtn.- Crossover Peak ridgeline, where not-so-prominent Mt. Parkes resides. Named for mountaineer Fred H.H. Parkes who was the first to ascend Slesse Mtn. in 1957. He also located the wreckage of the TCA passenger plane which crashed into Slesse Mtn. in 1956.
‘Spencer Ridge’ – a low, partially wooded ridge incorporating Mt. McGuire, Spencer Peak and Canadian Border Peak. Large clearcuts encroach on this ridge at various locations.
Mt. Lindeman – a prominent, rugged summit located along the Chilliwack River – Centre Ck divide overlooking ‘Upper Hanging Lake’.
GLACIERS OF THE SKAGIT RANGE
Glaciers currently exist within the Chilliwack River watershed and along its boundaries. From the late 1800’s to 1944 was a period of warming and retreat of glaciers which resulted in ~300 glaciers completely melting in the North Cascades. Another study showed that 47 glaciers within the North Cascades had lost significant ice mass between the years of 1984-2002 including 4 which had completely disappeared. It appears as though the same can be said for the glaciers within the Skagit Range. Many glaciers here have receded or disappeared due to warming.
Most of the glaciers which still exist today within the Skagit Range are found within: Cheam Ridge, Mt. Slesse area, Rexford Group/Illusion Group area, Mt. Lindeman and the Canadian Border Peak area. These alpine glaciers are found mainly on steep N, E and NE aspects (i.e. facing slopes). Many of these are relatively small glaciers although some of the glaciers along Cheam Ridge are sizeable. Some of the small glaciers here are positioned along steep slopes which can cause the ice to be unstable or discharged suddenly downslope. It has been observed that the ice can be reformed later, only to undergo another cycle of discharging.
NOTABLE LAKES & PONDS OF THE SKAGIT RANGE
Chilliwack Lake is the largest lake within the Skagit Range covering an area of approx. ~1,198 ha (2,959 acres). The average depth is ~69 m (226 ft) and its maximum depth is ~114 m (374 ft). The lake is located at ~625 m (2,050 ft) elevation and sometimes freezes over in winter. The lake is periodically stocked with fish and contains cutthroat, rainbow trout, dolly varden, kokanee and whitefish. The lake is fed by the upper Chilliwack River which drains a significant area S of the Canada-USA border. The lake is also fed by Paleface Ck and Depot Ck. Approximately 27% of the Chilliwack River watershed drains into Chilliwack Lake. Sandy beaches are found at the N end, S end and at the mouths of some tributary creeks.
Cultus Lake is a warmer, shallower, low elevation lake set at an elevation of ~45 m (148 ft). The area of the lake is ~627 ha (1,550 acres). The average depth is ~23 m (75 ft). Maximum depth is ~42 m (138 ft). The lake is periodically stocked with fish and contains cutthroat, rainbow trout, dolly varden, kokanee, steelhead, whitefish, coho and sockeye salmon. There is some development around the lake. Frosst Ck is the main tributary creek and the Sweltzer River drains the lake to the Chilliwack River. The word ‘cultus’ is taken from the Salish language to signify the evil spirits which were believed to live within the lake and sometimes displaying themselves as ‘dirty swirlings’ in the water. Another Salish word used to describe these evil spirits was later anglicized to ‘sweltzer’ which became the name of the river draining this lake.
Jones Lake (aka Wahleach Lake) is a large BC Hydro reservoir which backs up onto the E slopes of the Cheam Ridge. The reservoirs area is approx. 460 ha with an average depth of ~13 m (43 ft). There are campgrounds here and further W are scattered unofficial campsites. The maximum depth is ~29 m (95 ft). Rainbow trout and kokanee grace this lake. Main sources include Flat Ck and the drainage flowing E from Cheam Ridge.
Foley Lake is a smaller (~9 ha), low elevation lake accessible by road (periodically depending on the road condition). Good unofficial campsites are found here and a nice waterfall is located near its N shore. Fed and drained by Foley Ck.
‘Radium Lake’ is set just below treeline and is only accessed by trail. Some room for camping exists near the ruins of an old cabin. But best of all, great hikes further up the trail beckon.
Small Pierce Lake is also set just below treeline, has limited camping area and offers some killer hiking further up the trail. Located above treeline, ‘Upper Pierce Lake’ is one such example where great views are granted along the crater-like lake shore or even better above on the many ridges or peaks. It is likely that ‘Upper Pierce Lake’ originated from glacial activity, perhaps as a small glacier or large cirque.
Alas! No longer accessible by trail, Hanging Lake is now unseen and withdrawn amongst its rugged and glaciated surroundings. Likely originating as glacier or cirque, just as its companion ‘Upper Hanging Lake’ above. These lakes drain to upper Chilliwack River.
Tarn-like Williamson Lake sits below the rugged walls of Stewart Peak upon a ledge. Accessed by trail, camping-with-a-view can be had here. Multiple possible scrambling routes radiate outwards and upwards.
Tiny ‘Spoon Lake’ is a pleasant, curious looking tarn sitting within the beautiful meadows below Lady Peak and Cheam Mtn. Trails pass quite close to this almost perfectly round ‘lake’ held within its steep and uniform sides. Drainage is made to Spoon Ck. This tarn is a result of high magnitude avalanche activity – see below for more info.
Surrounded by private land, small Ryder Lake rests with a rural locale of Chilliwack. This lake does not appear to be accessible but can be glimpsed from the road. Drains to Ryder Ck.
Ling Lake has long been inaccessible as its backroads and trails have succumbed to nature. Situated within open forest and meadows, this picturesque lake is sorely missed! Mt. Ling resides nearby. Drains to Foley Ck.
Popular for its accessibility and camping, pleasant Lindeman Lake attracts many outdoor enthusiasts. With an elevation of ~838 m this lake is one the lowest elevation lakes in the region with basic camping facilities requiring human propulsion for access. This lake is situated right along the trail and beneath the spires of ‘The Gargoyles’. Area covered is ~11.6 ha with an average depth of ~7.9 m and a maximum depth of ~20.0 m. Further on up the trail is Greendrop Lake (1,020 m), which is a well liked camping area situated amongst old growth forest. Area covered is ~20.9 ha with an average depth of ~18.4 m and a maximum depth of ~48.0 m. A third lake, Flora Lake, connected by trail makes for a possible circuit between all 3 lakes. Partially filled by scree like Lindeman Lake, Flora Lake (1,356 m) is the highest lake of the three yet is still below treeline. Post Ck feeds Lindeman Lake and drains all 3 lakes. Scree has partially blocked the outlet of Greendrop Lake, causing the drainage to take place below the ground’s surface – a common occurrence in this scree prevalent area. Some massive blocks of granitic rock have also made their way down slope – some reside alongside the trail just below Lindeman Lake.
Remote Liumchen Lake is located within the Liumchen Ecological Reserve, a reserve established to protect low-mid elevation habitat, hydrology and landforms of the North West Cascades. Also, protection is provided for special features including rare and endangered species, critical habitats, and unique geological features. Rare and complex ecosystems exist here due to the limestone based soils of the area. The lake is small and shallow, but nicely set amongst old growth forest with meadows nearby. Drainage occurs ultimately to Liumchen Ck.
A hidden gem is Cheam Lake, which supports a large surrounding wetlands area. Including wetlands the lake covers ~12 ha and supports a wide variety of water fowl, frogs, beaver, and various aquatic life. Board walks allow visitors to access viewpoints near the center of the lake. Trails lead around parts of the lake and surrounding wetlands as well as along the creek which drains to the Fraser River. Interestingly, this lake was once a marl (limestone) mine which excavated a pit which was subsequently reclaimed to produce this lake. One would never know…
Unassuming ‘Anderson Pond’ lies against the TCT very near to Chilliwack Lake Rd. The pond was constructed using an old bend of the Chilliwack River that had been cut off by the construction of Chilliwack Lake Rd about 40 years ago. The pond is connected to the Chilliwack River and is used by Fisheries and Oceans Canada as quiet water spawning habitat for coho, steelhead, bull trout and cutthroat trout. The pond covers ~1.5 ha. Several other such ponds have been constructed in the area for the same purpose and can be seen from the TCT.
Sardis Pond, located within a residential area is a sanctuary for many forms of water fowl including Mute Swans. A park with trails surrounds the pond.
RIVERS & CREEKS OF THE SKAGIT RANGE
The Chilliwack River extends ~20 km within Washington State to cross the Canada-USA border and flows into Chilliwack Lake – this section is often referred to as the ‘Upper Chilliwack River’. The Little Chilliwack River flows into the Chilliwack River just S of the border. From the outlet of Chilliwack Lake, the Chilliwack River flows ~40 km to pass under Vedder Crossing (bridge) and drops from ~610 m elevation to ~40 m elevation over this section. At Vedder Crossing the river changes its name to the Vedder River which flows ~8 km to enter a canal structure built in the 1920’s in an effort to drain Sumas Lake (now called Sumas Prairie) as well as to contain the rivers significant spring freshet. See www.bcheritage.caView from Mt. Rexford Trail across Slesse-Nesakwatch divide and the USA border to Mt. Baker for photos of Sumas Lake. Within the canal, the river is called Vedder Canal which extends ~5 km. The Vedder Canal drains to the Sumas River for its short travel to the nearby Fraser River. To view a map of the historical drainage pattern of the Chilliwack River drainage go to: www.chilliwackwatershedstrategy.ca
Historically the Chilliwack River flowed N from Vedder Crossing over a wide delta to its confluence with the Fraser River. In 1882, a log jam was constructed to divert the river to the W into then, Sumas Lake. A freshet in 1894 helped to further channelize the river. In the early 1900’s dykes were constructed downstream from Vedder Crossing to prevent against floods and the river was further channelized. Recently, more dyke work has been conducted upstream from Vedder Crossing due to some localized flooding events.
Many sections of the Chilliwack River are fast flowing making it ideal for river kayaking and rafting. Overall, the river is rated Class II to Class IV and is known to contain boulder gardens, large rocks, blind corners and the odd sweeper is possible. The average daily flow is ~64 cms and the maximum daily discharge can reach >300 cms in May, June and December – February as measured at Vedder Crossing. Chilliwack River flow is currently monitored at Vedder Crossing, above the Slesse Ck confluence and at the outlet of Chilliwack Lake. Check out Environment Canada’s monitoring data at www.wsc.ec.gc.ca (input ‘chilliwack’ as station name). The averaged data show that the flow of the Chilliwack River increases significantly starting in April, reaches a maximum flow in June, drops to low flow in late August-early October, ramps up again to a second (although lower) peak flow in November before dropping to a low flow from January – April. The source of river water is snowmelt from spring to summer, intense rainfall in the winter and periodic rainfall year round. The District of Chilliwack has conducted investigations into utilizing Foley Ck as a source of drinking water.
The Chilliwack River can be characterized between the Camp Foley FRS on Chilliwack Lake Rd and Vedder Crossing as follows:
Between Chilliwack-Foley FRS (near Chilliwack Lake Rd crossing of Chilliwack River) and Slesse Ck confluence – this ~8.8 km section of river with class IV rapids is often referred to as ‘The Canyon’. At certain levels of lower and higher water flows, the technical difficulty of running the river increases.
Between Slesse Ck confluence and ‘Tamihi Bridge’ – this ~8 km section of river with class III rapids ends with Tamihi Rapids, the most difficult of this section.
Osborne Rd put-in to Vedder Crossing – includes ~8 km of class II rapids. At low water, the going can be humdrum.
MAJOR TRIBUTARIES TO THE CHILLIWACK RIVER
Upper Chilliwack River tributaries include Brush Ck, Indian Ck, Bear Ck and Little Chilliwack River.
Tributaries of Chilliwack Lake section include Depot Ck and Paleface Ck.
Tributaries below Chilliwack Lake include Post Ck, Radium Ck, Centre Ck, Nesakwatch Ck, Foley Ck, Chipmunk Ck, Pierce Ck, Slesse Ck, Tamihi Ck, Liumchen Ck and the Sweltzer River.
The largest tributary is Slesse Ck, having a length of ~25 km and whose drainage spreads S of the Canada-USA border. Below the significant confluence with Slesse Ck, the Chilliwack River widens to almost double its prior width. Within the USA the creek is known as Silesia Ck. For a brief time in 1951, Slesse Ck was renamed as Silesia Ck but was changed back. The earliest known name for the river was ‘Salacee Ck’ in 1860 used in an International Boundary Survey Report. The flow of Slesse Ck is monitored just upstream from the Chilliwack River – Slesse Ck confluence. Check out Environment Canada’s monitoring data at www.wsc.ec.gc.ca (input ‘slesse’ as station name). The flow of Slesse Ck is similar to that of the Chilliwack River (see above).
Liumchen Ck was originally called ‘Lihumitson Ck’ in 1936 and was changed to its current name based on established local spelling. The name is based on the Halkomelem (language of the Coastal Salish people) word meaning of ‘water gushing out’ as from an underground stream.
Nesakwatch Ck was once known as En-saw-kwatch Ck from the Halkomelem word referring to ‘a reed which once grew abundantly along the banks of this stream and was used for making fishnets.’
Tamihi Ck is called Tomyhoi Ck in Washington State. Originally referred to as ‘Tummeahai Ck’, the name is based on a Halkomelem name for nearby Mt. McGuire, meaning ‘deformed baby finishes’. It is supposed that ‘such infants were sometimes left on the mountain to die’.
Depot Ck was likely named after a nearby supply depot of the commission that surveyed the Canada-USA boundary from 1858-1861. The creek was also known as ‘Brown Ck’, named after a US Army infantry soldier who helped to escort the commission and who died by drowning in Chilliwack Lake in 1858. He was subsequently buried beside the creek.
WATERFALLS OF THE SKAGIT RANGE
In an area with such rugged terrain, significant waterfalls would be expected and this area does not disappoint. The most famous is, of course, Bridal Falls. This glorious waterfall is Canada’s sixth highest waterfall at 122m (~400 ft). This water fall sits within Bridal Falls Provincial Park off Hwy 1. It is an easy walk to view this waterfall.
The second most well known waterfall here is ‘Elk Creek Falls’ (aka ‘Elk Falls’). This large waterfall has no official name.
Many other less significant waterfalls exist within the Chilliwack River valley. The lower ramparts of Cheam Ridge and the lower E slopes of Slesse Mtn. display several cascading streams. Also, there is a nice waterfall on the N side of Foley Lake, along the Foley Ck FSR and Chilliwack-Paleface E FSR. There are also a few very nice, small waterfalls along the Chilliwack River FSR.
GLACIAL & POST GLACIAL LANDFORMS OF THE CHILLIWACK RIVER VALLEY
SW BC, including the Chilliwack River watershed and the Skagit Range Mountains, has undergone several periods of glaciation in the past. The last glaciation, known as the Fraser Glaciation, was characterized by a large ice sheet connecting to mountain ice fields and mountain glaciers which lasted ~6,000 years and ended ~10,000 years ago in the Fraser Lowland. At its height, the ice sheet is believed to have been ~2,000 m thick over the larger valleys in SW BC. Peaks higher than ~2,000 m, such as the majority of Cheam Ridge’s peaks for example, projected above the ice. The melting of the ice sheet occurred within a period of ~2,000 years which is considered to be quick. Researchers believe that a glacial lake (called a proglacial lake) formed which covered the majority of the Chilliwack River valley. As the ice melted more quickly in the upper elevations, the run-off was subsequently blocked by the unmelted ice below to cause a large lake to form.
The generation of sediments from glacial and related processes in BC is deemed by researchers to be greater than that which occurred during non-glacial periods even though the landscape was ice-free most of the time. This shows that the power of ice sheets and glaciers to scrape, grind and crush rock is immense. Rock material was also pushed and shaped by ice and carried by melt water to be deposited downstream.
The most widespread glacial material to be found is till which is an unsorted mix of clay, silt, sand, gravel and boulders. This material is carried by melting ice and is deposited about in a non-uniform manner. This material is common within the lower elevations of the Chilliwack valley, tributary valleys and lowlands and can be seen in many locations here such as road cuts. Sands and gravels (glacial-lacustrine materials), present throughout parts of the valley bottoms, were carried by the melt waters and deposited into the former glacial lake. Currently, the Chilliwack River flows through such glacial-lacustrine clays and silts which once sat at the bottom of the glacial lake. In the Fraser Lowland these types of deposits combined with glacial-fluvial sediments deposited by rivers of melt water can be up to hundreds of metres thick.
Cirques and related landforms due to alpine glaciation are common to the Skagit Range mountains. Ice-free cirques are common to this area and these often become tarns or lakes such as ‘Upper Pierce Lake’ and Williamson Lake. An absence of significant moraine (mix of rock material from silt to boulders) near these cirques indicates that the cirques were not occupied by ice for a significant length of time. Some alpine glaciers still exist near some of the higher peaks of the Skagit range such as Cheam Ridge and Slesse Mtn. There is significant moraine present near some of these cirques.
Alpine glaciation has resulted in the formation of some very steep walled peaks within the Skagit Range yielding formations such as spires and horns. Some impressive examples of this are Canadian Border Peak, Cheam Range peaks, Mt. Rexford, Nesakwatch Spires and Williams Peak.
Another glacial feature found within this region is the U shaped valley bottom such as that of the Chilliwack River valley. This shape indicates that a large body of glacial ice carved the valley walls and bottom from a ‘V’ shape to a ‘U’ shape.
SNOW AVALANCHE LANDFORMS OF THE CHILIWACK RIVER VALLEY
Successive high magnitude snow avalanches can cause the formation of certain landforms under certain conditions. These are rare in western Canada but one has been documented in upper Chipmunk Ck drainage: ‘Spoon Lake’. This small circular tarn sits at the base on Lady Peak along the Mt. Cheam Trail. Studies by Johnson et al., 2009 have found that 2 avalanche paths emanating from Cheam Ridge converge at the tarn (~1,470 m elev.). Based on tree ring data it is estimated that high magnitude snow avalanches occur here every 11 years. Boulders up to 1,000 kg deposited by such avalanches have been found in the vicinity of the tarn.
HAZARDS OF THE CHILLIWACK RIVER VALLEY
Several hazards exist within the valley area which are linked to the geology and glaciation which occurs here. Debris flows (including soil/sediment slope failures & mud flows) are a real danger here especially during the winter months when extended heavy rainfall occurs soon after snowfall has occurred. Extensive debris flows occurred within the lower Chilliwack River drainage in 2009 predominantly in the lower Tamihi Ck, Cultus Lk, Vedder Mtn, Baker Trails (S slopes of Promentory) and Western Hillsides areas which led to significant destruction to homes and property. Also, several significant landslides have occurred right along the Chilliwack River between Thompson Park and Pierce Creek. Debris flows are common to some backroad areas which can cause periodic closures of these roads. To see a map showing landslide locations in the Chilliwack River watershed go to: www.chilliwackwatershedstrategy.ca.
Landslides of primarily rock material are common to this area. See ‘General Bedrock Geology” section for info on the huge slide which occurred SW of Mt. Cheam. Another example is the Tolmie Slide which occurred within the lower Chilliwack River valley.
Flooding is a hazard which is ever present. Floods from the Chilliwack River and Vedder River have occurred many times in the past. Many dykes have been built to control the flood waters. Recent work has been done to build up dykes within the lower sections of the Chilliwack River to help mitigate this risk. Significant flooding occurred in January 2009 in Sumas Prairie, Greendale and other areas nearby. Flooding usually occurs in early summer, however this shows that it can happen here in the winter months as well. For a map of floodplain hazards in the Chilliwack River watershed go to: www.chilliwackwatershedstrategy.ca.
Other hazards characteristic of this area include snow avalanches, lightning (especially in high elevations) from thunderstorms in the summer, erosion caused by excessive logging, river/creek bank erosion, and fissures/sink holes in limestone areas.
For more info on the Chilliwack River watershed go to: www.chilliwackwatershedstrategy.ca
– Chilliwack River Watershed: A Backgrounder. By the Fraser Valley Regional District for the Chilliwack River Watershed Strategy. October 12, 2005. From website: www.chilliwackwatershedstrategy.ca
– Cascade Alpine Guide, Climbing & High Routes, No. 3: Rainy Pass to Fraser River, 3rd Edition, Fred Beckey. Geography, geology and history sections, pgs 8-22, 2008.
– BC Geographical names website for geographical names and some history information: https://archive.ilmb.gov.bc.ca/bcnames/
– The Current Disequilibrium of North Cascade Glaciers, M. Pelto, Hydrol. Process. 20, 769–779 (2006). Used for general info re: glacier changes in N. Cascades
– Archived Hydrometric Data, Water Survery of Canada website for general information re: Chilliwack River flows. https://www.ec.gc.ca/rhc-wsc/ (Data Products & Services > Hydrometric Data).
– Geomorphology of Snow Avalanche Impact Landforms in Southwest Canadian Cordillera, A. Johnson & D. Smith, The Canadian Geographer, 2009.