Upon his arrival in York, Simcoe was keenly aware of the need for a lumber mill and grist mill in the area. He had constructed a sawmill on the west bank of the river near present-day Bloor Street in 1793, which was operated by John Wilson. In 1797 Simcoe managed to get a grist mill established on the Humber River. It was owned and operated by John Lawrence. Over the years, numerous mills have been operated along the river by such men as William Cooper, W. P. Howland, Thomas Fisher, John Scarlett, William Gamble and Joseph Rowntree. The last grist mill on the Humber, Hayhoe Mills in Woodbridge, closed in 2007.
By 1860 the Humber Valley was extensively deforested. This decreased the stability of the river banks and increased damages done by periodic flooding. In 1878 a disastrous flood destroyed the remaining water powered mills. As the Toronto area grew, the lands around the Humber became important farming areas; in addition, some areas of the river’s flood plain were developed as residential. This led to serious runoff problems in the 1940s, which the Humber Valley Conservation Authority was established to address. But in 1954, Hurricane Hazel raised the river to devastating flood levels, destroying buildings and bridges; on Raymore Drive, 60 homes were destroyed and 35 people were killed.
The mills initially were for lumber, but later were mostly for grain. And when the distilleries were in full production, the mills were not needed. Whiskey financed Canada at the time of confederation. Read about it here!
Mill ponds drastically altered the valley with channels feeding and draining mill ponds. But after a storm in 1878 washed away the remaining mills, the water powered mills on the Humber were replaced by mills in Toronto powered by steam.
Gravel,sand, clay, and shale were all removed from Toronto’s valleys. This altered water flow in the valleys, and now massive flooding in the lower parts of the rivers is more common.