The Irwell, sourced at Cliviger in Lancashire, flows from the north and for a distance forms the statutory boundary between Salford and Manchester. Flooding has historically been a problem and the Irwell has seen much modification along its course in Salford with some bends being removed, channelisation, and the construction of levees and bank reinforcements. Salford has expanded along the river valley to the north and south and on to higher ground on the valley sides at Irlams o' th' Height and Higher Broughton. Unconsolidated glacial deposits along the riverbank at Broughton have caused several landslides along the riverbank. The City Engineer's Department of the City of Salford recorded one such incident near Great Clowes Street in February 1882, and others in 1886, 1887 and 1888. In 1892 the road was propped with timber supports. The tram service along the road was discontinued in 1925, and the road closed to mechanically propelled vehicles in January 1926. Further slips saw the road closed completely in July 1933, and although no substantial movements have been recorded since 1948 slow subsidence around the Cliff continues to this day.