Drainage Design Manual, Hydrology - Flood Control District of ...

Drainage Design Manual for Maricopa County
Hydrology: Acknowledgements, Comments & Revisions
Chapter 3 - The RATIONAL.EXE program has been updated to better match 10-year rainfall
intensities for durations between 10 and 20 minutes as shown on the I-D-F curve, . The revised
program is supplied on the DDMS diskette available with this revision (see 6. below).
Chapter 4 - A table has been added to help with the selection of IA, RTIMP, and percent vegetation
cover for representative urban land use types in Maricopa County.
Chapter 5 - Two new S-graphs have been added for use in Maricopa County. The newly added
S-graphs are the Desert/Rangeland S-graph and the Agricultural S-graph. A table has also been
added to facilitate the selection of S-graph type and K n values for those S-graphs for estimation
of basin lag time.
Chapter 6 - The Normal-Depth routing method has been added to the Manual as an additional
routing method for use in flood hydrology studies in Maricopa County.
Appendix I - A new computer program and user's guide have been added to this revision of the
Manual. The new program brings together the PREFRE program, a modified version of the loss
parameter spreadsheet functionality, and the MCUHP programs to speed up the creation of
HEC-I models using the methodologies recommended in the Manual. Additionally, two changes
have been made to the MCUHP programs. First, the SCS Type II 24-hour design storm temporal
distribution has been corrected and is now entered into the HEC-I data file as a 15 minute distribution.
Second, the two S-graphs added to Chapter 5 have been incorporated into the MCUHP2
program.
Appendix K - An appendix of K n values for various real watersheds has been supplied for additional
help in the selection of watershed K n values. These data were taken from a report by
George V. Sabol Consulting Engineers, Inc., performed for the District since the last Manual revision.
Overview of Changes Made For The Fourth Edition
All Chapters - Policies and standards were removed to a separate volume entitled Policies and
Standards for Maricopa County, Arizona, 2003. This allows each jurisdictional entity to customize
its policies and standards to meet its community’s needs. Also all references to the MCUHP
programs were changed to DDMSW.
Chapter 1 Introduction – In general, the contents were reformatted into a single section. Also,
a brief discussion of the contents of each chapter was added.
Chapter 2 Rainfall – The table identifying design rainfall criteria is eliminated as this information
is listed in the Policies and Standards for Maricopa County, Arizona, 2003. Procedures for deter-
iv August 15, 2013