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Geo Chap 14

# Geo Chap 14 - Chapter 14 Page 1 Geological Catastrophes...

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March 11, 2008 Chapter 14; Page 1 Geological Catastrophes Lecture: Chapter 14 I. Types of Floods A. Flash Flood 1. Intense rain over small area in short time (local storms) 2. Fast moving runoff B. Regional Flood 1. Sustained rain over large drainage 2. Slow rise and fall II. The Hydrograph A. A graph of the flow (discharge) in a stream over a period of time (can be months, years) III. Stream Response to a Storm A. There is a lag time between storm and stream response (takes time for groundwater runoff to make it to streams) B. As you move down the stream, the hydrograph curve gets flatter and wider IV. Recurrence Interval A. RI = (N+1)/M 1. N is the number of years of flood records 2. M is the numerical rank of the flood B. Can be turned into a probability by dividing the recurrence interval into 1 (1/RI) C. The probability is the percent chance of that flood happening in a given year D. Example: Given 99 years of flood records, the RI for the worst flood (largest discharge, M=1) is 100 years: RI=(99+1)/1=100 E. Longer records give more accurate Recurrence Intervals, and provide better estimates of worst case V. How Rivers and Streams Work A. Longitudinal Cross Section of a Stream (profile) 1.

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Geo Chap 14 - Chapter 14 Page 1 Geological Catastrophes...

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