HYDROMETEOROLOGICAL ASPECTS OF FLOOD HAZARDS IN CANADA

Floods are major natural disasters in Canada and worldwide. Although t echnology has reduced the flood hazard in many areas, the world death toll from floods in recent decades still has averaged 4680 per year. D uring the summer of 1993, flooding in the U.S.A. caused an estimated $ 12 billion damage. These statistics confirm that floods are a major na tural disaster. This paper reviews the hydrometeorological aspects of the hazard associated with rainstorm, urban, ice-jam, and snow melt fl oods. The hazard element is highest for floods with rapid onsets such as rainstorm, urban, and ice-jam floods. Although snowmelt floods are common throughout Canada, their slower onset times reduce their risk p otential. To reduce the risk of the flood hazard, society must have ac cess to statistical information for adequate planning and design, and forecasts for issuing warnings and implementing evacuation, strategies . Flood design statistics and forecast models are discussed relative t o each major flood type. The paper also describes historical flood fre quency trends and discusses the implications of climatic warming for f uture floods. The paper concludes with a brief discussion of some know ledge gaps and research needs.