Rational Method Local Hydrology Analysis. Consultant will utilize the existing CSDP No. 4 update hydrology for all local facilities within the City. Consultant will review and update, if necessary, the County files with the most recent City’s “ultimate” land uses. Since the CSDP No 4 hydrology only calculated flows for the 100-year storm, Consultant will have to perform calculations for the 10-year and 25-year events, for the local watersheds only. The AES Software hydrology model will be used to develop a link-node model for the critical concentration points previously identified in the mapping phase. These locations will generally follow the existing rational method boundaries, but will need to be modified based on future drainage needs (i.e. future catchbasins, or drainage laterals). Flowrates developed will be limited in minimum tributary drainage area size to the master plan or primary backbone facility systems only (i.e. flowrates will not be calculated for each individual surface inlet, unless through separate addendum). Hydrology calculations will be competed in accordance with the San Bernardino County Hydrology Manual. All areas over 640 acres will be evaluated using the Unit Hydrograph method. It is assumed that most of the hydrology (characteristics, parameters) can be estimated from the SBCFCD CSDP #4 report 100-year storm event recently updated in February 2013.
