GEOL 1 Lecture Notes - Lecture 23: Thunderstorm, Big Thompson River, Fuel Oil
Document Summary
Disruption to utilities [power lines, gas/oil pipelines] Flood magnitude or size can be measured by discharge [actual amount of water] or stage (height above bed) Floods usually reported to public as 10 year , 50 year etc floods. This is based on average recurrence interval. The larger the flood magnitude, the greater the recurrence interval. Term is confusing, public thinks 100 year floods occur exactly 100 years apart every time. Recurrence intervals calculated using data that exists and statistical analysis. R = n+1/m where n is the number of years in the data set. A curve fitted to data can be used to estimate 10 year, 20 year etc. floods. To find the probability that this size event would occur in any given year, find the reciprocal of the average interval: 0. 02 x 100 = 2% probability [every year] Highest priority is given to areas with densest populations and high-value property. Mitigation in one area may cause worse floods elsewhere.
