Before the canal, this was a shallow freshwater lake of about 4,000 hectares, ringed by wetlands, swelling far wider in flood season and shrinking in summer. Sturgeon, trout and salmon used it. Migrating birds bred in the marshes, and grizzlies came down to the shores. The Sema:th people, a Sto:lo community, had their centre here - their name comes from the thick grass and reeds standing in the shallows at the lake's edge. As Chief Dalton Silver has described it, people gathered at Sema:th in summer to fish and in winter for ceremony. It was the place everyone came back to. A lake that fills and empties with the seasons looks like an obstacle if you intend to plough it, and like a larder if you have lived beside it long enough to know when the sturgeon run.

The great Fraser flood of 1894 made the argument, and the engineer Fred Sinclair drew up the plan. Between 1920 and 1924 the Chilliwack River was diverted into a new channel - the Vedder Canal - and the lake was drained north through the Sumas Drainage Canal into the Fraser. It was a monumental piece of work and a financial disaster: costs ran far past projections, and the reclaimed ground turned out to be less fertile than the promoters had promised, selling to settlers in the 1930s for sixty to a hundred and twenty dollars an acre. The Sema:th were not compensated for the loss of the lake that had defined them. A century later the Sumas First Nation was pursuing a specific land claim over it. You cannot drain a lake halfway. The decision, once made, was permanent for everyone who had depended on it.

What replaced the lake is farmland of real consequence - dairy, poultry, berries, corn - spread across a dead-flat basin between Abbotsford and Chilliwack, with Highway 1 running straight across the old lakebed. Administratively it was the District of Sumas until 1972, when it was folded into Abbotsford; the northeast corner around Yarrow went to Chilliwack. The land stays dry because water is lifted off it, continuously, by pumps at the north end. The record is instructive. Fraser freshets pushed water back over the prairie in 1894, 1948, 1972 and 2007. Extreme rainfall did it in November 1990, in November 2021, and again in December 2025. Between events the basin looks like ordinary agricultural country. That is the trick of it: a floodplain is only a floodplain on the days it decides to be one.

The November 2021 flood became the costliest natural disaster in British Columbia's history - at least $450 million in insured damage, with total regional losses estimated in the billions. Eleven hundred homes in Abbotsford were evacuated, and ninety more in Huntingdon Village on November 28 when the Nooksack overtopped again. The hardest number to sit with is the livestock: as many as 630,000 animals died, most of them poultry, drowned in barns that farmers could not reach. Dairy herds were driven out through chest-deep water by neighbours in boats. On November 19, with a dike broken and the Barrowtown pumps at risk, the mayor announced that the Canadian Army would build a levee across the gap - a decision that meant deliberately flooding about a dozen homes to keep the water off thousands. Those are the choices a place makes when it lives on the floor of a lake it has agreed not to have.