GEOL 2207 Lecture Notes - Outburst Flood
Document Summary
Probability of the ri-year flood: p=1/ri: ex. P(20 year flood) this year = 1/20 = 5% Probability based on historic data for a given stream/river. Shortcomings not enough record, may not accurately predict floods of large scale. Upstream floods-occur in upper parts of drainage basin: in small drainage basin, or head of large drainage basin, flood of high magnitude but short duration, trigged by extreme event: intense precipitation, ice jams, etc. Produced by intense rainfall of short duration over a small area. Flash floods sudden and large increase in discharge: common in arid and semi-arid environments, steep topography, little vegetation. Occur with little warning, fatalities often in cars. Major cause of flooding in canada (freeze up, break up) Accumulation of ice during break-up restricts river flow. During spring thawing: breaks up, move down rapidly down river, discharges quite high, ice blocks reach constrained area forms a dam. Outburst floods caused by sudden draining of dammed.
