Bailey bridge crossing

Press, 6 November 1984, Page 32

Bailey bridge crossing

Visitors to the "Waters of Canterbury” exhibition in Canterbury Court will have to cross a Bailey bridge to reach some of the displays.

The Ministry of Works and Development will install a Bailey bridge and access ramps over an artificial river to highlight the equipment needed to maintain road services in emergencies. Water is a common cause of emergencies, in the form of slips, washouts, floods, ice and snow. Small washouts and slips on roads are usually quickly repaired by ministry staff, often without the public aware of the damage. Bigger washouts may take a day to repair and replacing a bridge span may take a week. The Ministry keeps a stock of Bailey bridge spans in' Christchurch ready for emergencies in Canterbury and the West Coast. Restoring road links after storms and floods is just part of the work done by Ministry staff and is featured in the Waters of Canterbury exhibition. The Ministry’s display will fill about a quarter of Canterbury Court and will cover hydrology, rivers, irrigation and power generation. The Ministry keeps a

close eye on the movement of water throughout Canterbury. A series of rain gauges monitors rainfall in a line from the West Coast across the Southern Alps to the east coast, and regular measurements are made of the flow and height of rivers. . The velocity of a river is measured by a current meter, often suspended from a cable way above the river, or a jetboat. All this information is used in designing power and irrigation schemes, bridges and roads, river control works and in environmental and conservation projects as well as giving early warning of floods. The Ministry is installing a telemetry system to allow the monitoring of river flows from its Christchurch office, using radio signals to transfer the measurements from the recording sites. A 50-year-old turbine, previously used to' produce electricity at Braemar station, Lake Pukaki, will be on view as part of the power generation section. Also included will be a model of the Upper Waitaki power schemes.