# Shared Flashcard Set

## Details

4GEOG landscapes and water
Floods
12
Geography
04/04/2010

Term
 what is a hydrograph?
Definition
 a record of discharge in a river over time   most attention is paied to the peaks on a hydrograph - these are generally associated with rainstorms or snwomeld events
Term
 what is the peak flow?
Definition
 the highest discharge that occurs in a rainfall-runoff event   the peak on a hydrograph
Term
 what is the rising limb?
Definition
 the portion of the hydrograph leading up to the peak flow
Term
 what is the falling limb?
Definition
 the portion of the hydrography following the peak flow
Term
 what is baseflow?
Definition
 the discharge that the peak rises above, the background flow   it is supplied by groundwater from the catchment
Term
 what is storm flow and what supplies it?
Definition
 it is the rise in discharge during a storm   it is supplied by groundwaterand some combination of the flowpaths (HOF, SSSF, and SOF)
Term
 what is the lag-to-peak?
Definition
 the time delay between peak rainfall and the peak flow in the river
Term
 what is a floodplain? why is the definition important?
Definition
 the flat area adjacent to the river channel, constructed by the present river in the present climate and frequently subject to overthrow (definition from Luna Leopold, important b/c stresses the fact that rivers normally overtop their banks and flow on the adjacent floodplain)
Term
 what is a flood?
Definition
 if it is defined as flow outside the channel, then floods are a regular, frequent occurence in the landscape that happen when the flow is high enough to push the river out of its banks   to quantify the flood risk for a certain area/find where flood risk is low need to understand teh frequency and magnetude of high flows
Term
 How can you construct a curve to show the probability of a perticular discharge occuring?
Definition
 1. record the highest discharge each year for n years (or obtain the records for a location) 2. rank these annual floods according to discharge, with the largest discharge assigned rank 1, the second rank 2 etc 3. compute the recurrence interval for each flood. using: RI=(n+1)/m where RI is recurrence interval, n is the number of years in the record, and m is the rank of the flood 4. plot the discharge versus the recurrence interval using logarithmic graph paper
Term
 what is the 100-year flood?
Definition
 the flood that has a recurrence interval of 100 years
Term
 what is the probability of a particular flood happening in the coming year?
Definition
 the reciprocal the recurrence interval:   P=(1/RI)x100%   (the 100 year flood or RI=100 has a 1% probability of happening in any year while the 10 year flood has a 10% probability and the 2 year flood has a 50% chance)   if the 100 year flood happens this year, the probability is 1% and if it happens next year the probability is still 1%
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