Hazard classification guidelines and procedures

The presence of a dam creates an incremental hazard to the downstream development beyond that of other natural hazards not associated with the dam, due to the potential for dam failure and uncontrolled water release. The general hazard classification system used by Ontario Hydro is documented and further guidance is provided for the identification and classification of downstream hazards. Suggested methods of determining the preliminary hazard category are also documented. Hazard categories are selected for each structure under both normal and flood conditions, examining potential for increase in loss of life, and economic loss, social and environmental impacts. Analysis of downstream areas includes location of existing facilities, existing land usage and zoning, historical flows and water levels, information concerning previous flooding events, and physical parameters of the dam. Detailed analysis develops the probable maximum precipitation and flood information, and flood routing. Final confirmation of the hazard classification uses the definitive water level information to re-examine the probable loss of life and flood damages. 8 refs., 6 figs