The Fraser Valley is the region of the Fraser River basin in southwestern British Columbia downstream of the Fraser Canyon. The term is sometimes used outside British Columbia to refer to the entire basin including the Fraser Canyon and up from there to its source, but in general British Columbian usage of the term refers to the stretch of the river downstream from the town of Hope, and includes all of the Canadian portion of the Fraser Lowland and areas flanking it.
After descending through the rapids of the Fraser Canyon, the Fraser River emerges almost at sea level at Yale, over 100 km inland. Although the canyon in geographic terms is defined as ending at Yale, Hope is generally to be considered the southern end of the canyon, partly because of the change in the character of the highway from that point , and perhaps also because it is at Hope that the first floodplains typifying the course of the Lower Fraser are found. Downstream from Hope, the river and adjoining floodplains widen considerably in the area of Rosedale, Chilliwack and Agassiz, which is considered the head of the Fraser Delta. From there the river passes through some of the most fertile agricultural land in British Columbia--as well as the heart of the Metro Vancouver region--on its way through the valley to its mouth at Georgia Strait.
During the last ice age, the area that would become the Fraser Valley was covered by a sheet of ice, walled in by the surrounding mountains. As the ice receded, land that had been covered by glaciers became covered by water instead, then slowly rose above the water, forming the basin that exists today. The valley is the largest landform of the Lower Mainland ecoregion, with its delta considered to begin in the area of Agassiz and Chilliwack, although stretches of floodplain flank the mountainsides between there and Hope.
Several of the Fraser's lower tributaries have floodplains of their own, shared in common with the Fraser freshet. Of varying size these include the Harrison River, Chilliwack River (Vedder River), Hatzic Creek and Hatzic Lake, the Stave, Alouette, Pitt and Coquitlam Rivers. Also incorporated in the Fraser delta region are the Nicomekl and Serpentine River floodplains and the Sumas River drainage, which flow to saltwater independently of the Fraser but help drain its lowland. The Fraser is tidal as far upstream as the town of Mission and, across the river, the City of Abbotsford, which is at the Fraser's closest approach to the international boundary, about 6 miles north of Sumas, Washington. Pitt Lake, one of the Fraser's last tributaries.
Oxbow lakes and side-sloughs are a common feature of the Lower Fraser's geography. The two main oxbows are those of Hatzic Lake and the Stave River on opposite sides of Mission, although that of the Stave has been silted in and part of it drained for a man-made lake. Around Fort Langley is an oxbow formation, mostly swamped in at the time of the fort's foundation, which was drained and made part of the fort's farm and remains farmland today. The system of sloughs and side-channels of the river is complicated, but important sloughs include those around Nicomen Island, Sea Bird Island and flanking the river from Rosedale to Sumas Mountain, on the western side of Chilliwack.
This section of the Fraser River -- called "Sto:lo" in the Halqemeylem language of the area, and who have adopted it as the collective name for all the peoples of the Fraser Lowland, other than the Squamish and Musqueam -- was a vital lifeline before the first European contact, and has been an important transportation corridor ever since.
In the nineteenth century, steamboats plied the waters between Georgia Strait and Yale, and were especially busy during the gold rush from 1858 into the 1860s. Boats continued to provide a vital link in the valley as the gold rush tapered off and Europeans began farming.
Eventually, roads and railways were built, fueled by and in turn fuelling population growth. Today, the most important transportation through the region are the Canadian Pacific Railway and Canadian National Railway transcontinental main lines, the Lougheed Highway (Hwy 7), and the Trans-Canada Highway (Hwy 1).
According to the 2011 Census, 76.47% of Fraser Valley's population have English as mother tongue; Punjabi is the mother tongue of 10.02% of the population, followed by German (3.49%), Dutch (1.39%), French (1.07%), Korean (0.69%), Spanish (0.66%), Tagalog (0.35%), Chinese, n.o.s. (0.33%), and Vietnamese (0.30%).
Agricultural land in the valley - much of it protected by the Agricultural Land Reserve - is intensively farmed: the Fraser Valley brings in over half of British Columbia's annual agricultural revenue, although it makes up a small percentage of the province's total land area.
In winter, the Fraser Valley occasionally plays a significant role in the weather regime along the west coast of North America as far south as California, acting as a natural outlet for the intensely cold Arctic air mass which typically sits over Western Canada during winter. Under certain meteorological conditions strong winds pour out of the Fraser Valley and over the relatively warmer waters of the Strait of Georgia and the Strait of Juan de Fuca. This can cause ocean-effect snow, especially between Port Angeles and Sequim, where the air mass collides with the Olympic Mountains. The cold air from the Fraser Valley can also flow out over the Pacific Ocean. Lanes of convective ocean-effect clouds and showers are produced as heat and moisture modify the very dry, frigid air mass. These then typically organize as a low pressure system which returns the showers to the coast south of Canada, often bringing snow to unusually low elevations.
As the valley population grows and traffic increases, air pollution becomes an increasingly important issue; various controversies have risen over the years (most recently over "Sumas 2", a defeated proposal for a power plant just south of the Canadian/USA border) as to whether or not air pollution is a problem, and if it is a problem, how this should be addressed.
Air quality monitoring has improved in recent years and it is now possible to compare BC communities on a variety of measures. Comparative data on four measures--fine particulate matter, ground-level ozone, nitrogen dioxide and sulphur dioxide--shows the Fraser Valley to rank lower than Vancouver on several measures of air quality. For example, Fraser Valley communities had less than half the levels of nitrogen dioxide, and were lower in fine particulate matter and sulphur dioxide (on the latter measure, Abbotsford and Chilliwack were among the lowest of all BC sites).
In certain weather conditions during the summer, prevailing westerly winds blow air pollution from vehicles and from ships in Vancouver harbour east up the triangular delta, trapping it between the Coast Mountains on the north and the Cascades on the southeast. Air quality suffers. This usually occurs during a temperature inversion, and lasts for a few days. Ground-level ozone tends to be from local sources in the valley and varies with prevailing winds. With prevailing winds from the northeast during the late fall and winter, air quality is seldom a problem.
Air quality in the Fraser Valley at times exceeds the Canada-Wide Standard (CWS) for ozone (at Hope) and is close to exceeding the CWS for Particulate Matter.
In colloquial usage, "Fraser Valley" usually refers only to that part of the valley beyond the continuously built-up urban area around Vancouver, up to and including Chilliwack and Agassiz, about 80 km east, and abutting the border with Washington's Whatcom County; news media typically also include the built-up eastern suburban areas of Vancouver which a few decades ago were mixed farmland and forest, typical of "the Valley". The Fraser Valley region is also the namesake of the Fraser Valley Regional District, though that consists of only about half of the actual Fraser Valley, and is made up of the municipalities and incorporated areas from Abbotsford and Mission eastwards to Hope. It also includes areas not in the Fraser Valley, particularly the lower Fraser Canyon from Boston Bar to Hope.
The term "Central Fraser Valley" refers to Mission and Abbotsford and is included within the Lower Fraser Valley. The Upper Fraser Valley means from Chilliwack and Agassiz to Hope. The phrases "Fraser Valley towns" and "Fraser River municipalities" include Delta and Richmond, though the colloquial "in the Valley" means from Surrey and Coquitlam eastwards.
The "Tidal Fraser area" is usually known as the area of the Fraser from the mouth at the Pacific Ocean to the Mission bridge. Everything in between there is influenced greatly by ocean tides, including the largest tidal lake in North America, Pitt Lake.
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The south shore of the Central and Upper Fraser Valley is also known colloquially as the "Bible Belt" of British Columbia and is home to many of Canada's largest churches, notably the Mennonite Brethren and the Dutch Reformed Church, a reflection of the heavy settlement of the Valley by post-war Dutch and German immigrants, as well as the Canadian headquarters of many Christian/Evangelical para-church organisations such as Focus on the Family and Campus Crusade for Christ. Voters in south shore ridings typically elect right-wing candidates, while in ridings on the river's north side elections sway between left-wing and right-wing parties regularly.