Annual Peak Discharge of Fishkill Creek

HydroTools has been tested using the Fishkill Creek example in "Guidelines for Determining Flood Flow Frequency" (Bulletin 17B of the Hydrology Committee, U.S. Geological Survey, Reston, VA).  The annual peak flow data given below.  

Using a skew coefficient of 0.7, the reported value for the 100-year discharge is 1150 cfs.  Using the HydroTools LogPearson() function without specifying the skew coefficient (and thus having it estimated from the observed annual peak discharges), the estimated 100-year flood is 1170 cfs.  Specifying the skew coefficient to be 0.7 (to match the published analysis), the estimated 100-year discharge is 1160 cfs.  The slight difference between the published value and that estimated using the LogPearson() function reflects rounding errors.

The published value for the 1.01-year discharge is 841 cfs with 95% confidence limits of 568 cfs and 1100 cfs.  Using the HydroTools LogPearson() function with a skew coefficient of 0.7 and the confidence limits of 0.95, the estimated 1.01 year discharge is 838 cfs with lower and upper confidence limits of 565 cfs and 1092 cfs.  Again, the light difference between the published value and that estimated using the LogPearson() function reflects rounding errors.


Year      Annual Peak Discharge (cfs)
1945     2290
1946     1470
1947     2220
1948     2970
1949     3020

1950     1210 
1951     2490
1952     3170
1953     3220 
1954     1760

1955     8800
1956     8280 
1957     1310
1958     2500
1959     1960 

1960     2140
1961     4340
1962     3060 
1963     1780
1964     1380

1965       980
1966     1040
1967     1580
1968     3630

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