1.   Purpose and objectives

     To provide a user-friendly interactive computer package to analyse the data with respect to the underlying assumptions of flood frequency analysis and to perform flood frequency analyses using several frequency distributions.

2.   Description

     The CFA Package allows the user to: easily enter flood data for analysis; modify data sets so as to add, delete, or modify all stored information; save modified data sets for future use; perform nonparametric tests for homogeneity, trend, independence and randomness; graphically display data in various fashions; perform tests for low and high outliers; determine T-year events for the straightforward case, samples with historic information, samples with low outliers, samples with zero flow values, and 
combinations of these. The probability distributions available are:

         1)  generalized extreme value;
         2)  three-parameter lognormal;
         3)  Log Pearson Type III; and
         4)  Wakeby.

3.   Input

     Annual maximum daily or instantaneous discharge and the year and month of its occurrence constitute the data required for analysis.

     The censoring threshold and the number of floods where exact magnitudes are not known but which are known to have occurred and are less than the threshold can be included so that an historical flood frequency analysis can be performed. Data and historic information can be entered via the keyboard or read from mass storage devices.

4.   Output

     Results of nonparametric tests for homogeneity, trend, independence and randomness. Graphical displays of the data are also available as a visual aid in the assessment of the data regarding the assumptions of frequency analysis. Once a sample passes the screening procedure, a frequency analysis may be performed. Summary statistics in real and log (Naperian) formats are given for the flood data. Parameters of selected distributions, tables of design flood estimates, and frequency curves are available.

5.   Operational requirements and restrictions

     The current version of CFA software was written in Fortran 77 to run under DOS 3.1 on IBM-type microcomputers with a math coprocessor. However it can also be used on computers running Windows 95 and 98. 

     CFA was designed to be user friendly and interactive, thus no knowledge of programming is required to operate the package. Interpretation of results should be performed by analysts having knowledge
of the assumptions and limitations of the approaches, mathematical treatment, and implications regarding the selection of design floods.

6.   Form of presentation

     The user manual and appendices are in English. Diskettes contain an executable module and a sample data set.  

7.   Operational experience

     CFA has been applied to several hundred hydrometric sites in Canada and is currently widely used by government agencies and private industry. In addition, CFA has been distributed to individuals in over 15 countries.

8.   Originator and technical support

     Atmospheric Environment Service, Environment Canada.

9.   Availability

     Through the HOMS National Reference Centre for Canada

10.  Conditions on use

     Licences for CFA must be purchased from Greenland International Consulting Inc. Educational and multiple licence discounts are available.