Avon River (Nova Scotia)
Encyclopedia
The Avon River is a small Canadian
river
in central Nova Scotia
.
A northerly flowing river, the Avon River flows rises on South Mountain
, southwest of the town of Windsor
. Its meander length is 64 km (39.8 mi). Near the rural community of Martock
, the river enters a broad glacial river valley forming a ria
) where it becomes tidal
, creating an estuary
for its remaining route to the Minas Basin
several kilometres downriver from the town of Hantsport
.
Rivers flowing into the Avon include the Herbert, Cogmagun, Kennetcook
and St. Croix
.
immediately downstream from Windsor at its junction with the St. Croix River
as part of the development of a controlled access expressway called Highway 101
.
The Avon River Causeway replaced an existing road bridge upriver from town and also resulted in the rerouting of the Dominion Atlantic Railway
's Halifax-Yarmouth
main line which used to run through Windsor's downtown, crossing the river on a bridge parallel to the road bridge immediately upriver from the town.
The causeway controls the Avon River's discharge and the incoming tidal waters of the Minas Basin through a series of flood control gates which are intended to regulate the river's flowage to prevent flooding of agricultural lands upriver near Martock. The section of the Avon River upriver of the causeway along the Windsor waterfront is now the freshwater Pesaquid Lake.
The construction of the causeway has dramatically affected the Avon River downstream from Windsor, with large parts of the once-navigable river now being obstructed by large mud flats and vegetation, owing to the lack of tidal exchange and freshwater discharge. The nature writer Harry Thurston has noted, "Almost before the last stone was put in place, sediment began to accumulate to an alarming rate - 5 to 14 centimetres per month. Within seven years, a four metre high island of silt formed on the seaward side of the causeway; and the effects were felt 20 kilometres downstream, where two metres of mud impaired navigation at Hantsport."
Researchers soon discovered that the mud flats had become a biological desert
, devoid of life, as the sediments were too soft to support organisms. The need to monitor and assess the impacts of such changes gave impetus to a greater interest in Bay of Fundy
ecosystem and the ultimate establishment of the Acadia Centre for Estuarine Research in Wolfville.
Recently announced plans for the expansion of Highway 101 between the Halifax Regional Municipality and the eastern end of the Annapolis Valley
have raised concerns about maintaining the Avon River causeway. An environmental lobby group, Friends of the Avon River (FAR), has called for studies into the possibility of removing the causeway entirely and carrying the expressway and railway line on a new bridge, allowing the natural flow of the river course to be reestablished. FAR has also recently begun to oppose the expansion of gypsum quarries within the river's watershed because of threats to river life, citing the use de-watering runoff from the quarries.
A decision in August 2007 by the New Brunswick
government to remove a similar causeway (constructed in 1968) blocking the Petitcodiac River
, another tribuatary of the Bay of Fundy, to avoid facing charges under the federal Fisheries Act, is expected to have ramnifications for the Avon River causeway.
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
river
River
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...
in central Nova Scotia
Nova Scotia
Nova Scotia is one of Canada's three Maritime provinces and is the most populous province in Atlantic Canada. The name of the province is Latin for "New Scotland," but "Nova Scotia" is the recognized, English-language name of the province. The provincial capital is Halifax. Nova Scotia is the...
.
A northerly flowing river, the Avon River flows rises on South Mountain
South Mountain (Nova Scotia)
South Mountain is a Canadian range on the mainland portion of Nova Scotia. A granitic ridge stretching from the Annapolis Basin to Mount Uniacke, it forms the southern edge of the Annapolis Valley and shelters the valley from the climate effects of the pelagic coast along the Atlantic Ocean.In...
, southwest of the town of Windsor
Windsor, Nova Scotia
Windsor is a town located in Hants County, Mainland Nova Scotia at the junction of the Avon and St. Croix Rivers. It is the largest community in western Hants County with a 2001 population of 3,779 and was at one time the shire town of the county. The region encompassing present day Windsor was...
. Its meander length is 64 km (39.8 mi). Near the rural community of Martock
Martock, Nova Scotia
Martock is a rural Canadian agricultural community located in the Avon River valley of western Hants County, Nova Scotia.The community was named after Martock House which was the original home in the area. The Georgian style mansion was built in 1790 and originally boasted more than of land. Col....
, the river enters a broad glacial river valley forming a ria
Ria
A ria is a coastal inlet formed by the partial submergence of an unglaciated river valley. It is a drowned river valley that remains open to the sea. Typically, rias have a dendritic, treelike outline although they can be straight and without significant branches. This pattern is inherited from the...
) where it becomes tidal
Tide
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the moon and the sun and the rotation of the Earth....
, creating an estuary
Estuary
An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea....
for its remaining route to the Minas Basin
Minas Basin
The Minas Basin is an inlet of the Bay of Fundy and a sub-basin of the Fundy Basin located in Nova Scotia, Canada. It is known for its extremely high tides.- Geography :- Boundary :...
several kilometres downriver from the town of Hantsport
Hantsport, Nova Scotia
Hantsport is a rural Canadian town and seaport located in the western part of Hants County, Nova Scotia. Hantsport is located just south of the county boundary with Kings County, and sits on the west bank of the Avon River in a tidal estuary.The town is most best known for its history of...
.
Rivers flowing into the Avon include the Herbert, Cogmagun, Kennetcook
Kennetcook River
The Kennetcook River is a river that flows through Hants County, Nova Scotia. From headwaters near the mouth of the Shubenacadie River, the Kennetcook traverses about 45 kilometres of mostly rural terrain, discharging into the Avon River at Windsor. The Kennetcook cuts through fossiliferous...
and St. Croix
St. Croix River (Nova Scotia)
The St. Croix River is a river in Nova Scotia entirely contained in Hants and Halifax Counties. Its headwaters are Panuke Lake. The river has been exploited for water power. There were water mills in the nineteenth century and in the 1930’s three hydroelectric dams were built; they still...
.
Causeway and controversy
In 1970 the Avon River was completely obstructed by a rock and earth fill causewayCauseway
In modern usage, a causeway is a road or railway elevated, usually across a broad body of water or wetland.- Etymology :When first used, the word appeared in a form such as “causey way” making clear its derivation from the earlier form “causey”. This word seems to have come from the same source by...
immediately downstream from Windsor at its junction with the St. Croix River
St. Croix River (Nova Scotia)
The St. Croix River is a river in Nova Scotia entirely contained in Hants and Halifax Counties. Its headwaters are Panuke Lake. The river has been exploited for water power. There were water mills in the nineteenth century and in the 1930’s three hydroelectric dams were built; they still...
as part of the development of a controlled access expressway called Highway 101
Nova Scotia Highway 101
Highway 101 is an east-west highway in Nova Scotia that runs from Bedford to Yarmouth.The highway follows a route along the southern coast of the Bay of Fundy through the Annapolis Valley. Between its western terminus at Yarmouth to Weymouth, the highway is 2-lane controlled access. Between...
.
The Avon River Causeway replaced an existing road bridge upriver from town and also resulted in the rerouting of the Dominion Atlantic Railway
Dominion Atlantic Railway
The Dominion Atlantic Railway was a historic Canadian railway which operated in the western part of Nova Scotia, primarily through an agricultural district known as the Annapolis Valley....
's Halifax-Yarmouth
Yarmouth, Nova Scotia
Yarmouth is a town and fishing port located on the Gulf of Maine in rural southwestern Nova Scotia, Canada. It is the shire town of Yarmouth County. The town is located in the heart of the world's largest lobster fishing grounds and has Canada's highest lobster catch.- History :The townsite may...
main line which used to run through Windsor's downtown, crossing the river on a bridge parallel to the road bridge immediately upriver from the town.
The causeway controls the Avon River's discharge and the incoming tidal waters of the Minas Basin through a series of flood control gates which are intended to regulate the river's flowage to prevent flooding of agricultural lands upriver near Martock. The section of the Avon River upriver of the causeway along the Windsor waterfront is now the freshwater Pesaquid Lake.
The construction of the causeway has dramatically affected the Avon River downstream from Windsor, with large parts of the once-navigable river now being obstructed by large mud flats and vegetation, owing to the lack of tidal exchange and freshwater discharge. The nature writer Harry Thurston has noted, "Almost before the last stone was put in place, sediment began to accumulate to an alarming rate - 5 to 14 centimetres per month. Within seven years, a four metre high island of silt formed on the seaward side of the causeway; and the effects were felt 20 kilometres downstream, where two metres of mud impaired navigation at Hantsport."
Researchers soon discovered that the mud flats had become a biological desert
Desert
A desert is a landscape or region that receives an extremely low amount of precipitation, less than enough to support growth of most plants. Most deserts have an average annual precipitation of less than...
, devoid of life, as the sediments were too soft to support organisms. The need to monitor and assess the impacts of such changes gave impetus to a greater interest in Bay of Fundy
Bay of Fundy
The Bay of Fundy is a bay on the Atlantic coast of North America, on the northeast end of the Gulf of Maine between the Canadian provinces of New Brunswick and Nova Scotia, with a small portion touching the U.S. state of Maine...
ecosystem and the ultimate establishment of the Acadia Centre for Estuarine Research in Wolfville.
Recently announced plans for the expansion of Highway 101 between the Halifax Regional Municipality and the eastern end of the Annapolis Valley
Annapolis Valley
The Annapolis Valley is a valley and region in the Canadian province of Nova Scotia. It is located in the western part of the Nova Scotia peninsula, formed by a trough between two parallel mountain ranges along the shore of the Bay of Fundy.-Geography:...
have raised concerns about maintaining the Avon River causeway. An environmental lobby group, Friends of the Avon River (FAR), has called for studies into the possibility of removing the causeway entirely and carrying the expressway and railway line on a new bridge, allowing the natural flow of the river course to be reestablished. FAR has also recently begun to oppose the expansion of gypsum quarries within the river's watershed because of threats to river life, citing the use de-watering runoff from the quarries.
A decision in August 2007 by the New Brunswick
New Brunswick
New Brunswick is one of Canada's three Maritime provinces and is the only province in the federation that is constitutionally bilingual . The provincial capital is Fredericton and Saint John is the most populous city. Greater Moncton is the largest Census Metropolitan Area...
government to remove a similar causeway (constructed in 1968) blocking the Petitcodiac River
Petitcodiac River
The Petitcodiac River is a Canadian river in south-eastern New Brunswick. The river runs about through the province's Westmorland, Albert, and Kings counties, draining a watershed area of about . The region around the river features valleys, ridges, and rolling hills, and is home to a diverse...
, another tribuatary of the Bay of Fundy, to avoid facing charges under the federal Fisheries Act, is expected to have ramnifications for the Avon River causeway.
Further reading
- Danika van Proosdij and Sarah M. Townsend, "Sedimentation and Mechanisms of Salt Marsh Colonization on the Windsor Mudflats", in The Changing Bay of Fundy—Beyond 400 Years, 2004