R2003-0049 03-10-03 RESOLUTION NO. R2003-49
A RESOLUTION OF THE CITY COUNCIL OF THE CITY OF PEARLAND,
TEXAS, REVISING AND CLARIFYING PORTIONS OF THE CITY'S STORM
DRAINAGE DESIGN CRITERIA MANUAL.
WHEREAS, the city of Pearland, a home-rule municipality, is authorized by Charter
to adopt and implement necessary and reasonable regulations that are in the best interests
of its citizenry; and
WHEREAS, health and safety issues associated with the increased runoff caused
by development in the City are steadily increasing; and
WHEREAS, the City has determined the need to revise and clarify portions of the
City's Storm Drainage Design Criteria Manual to help mitigate the effects of increased
runoff caused by development.
BE IT RESOLVED BY THE CITY COUNCIL OF THE CITY OF PEARLAND, TEXAS:
Section 1. For purposes of determining storm water runoff in accordance with
Section 5.1 of the City's Storm Drainage Design Criteria Manual (SDDCM), all drainage
and detention designs in Pearland and its extraterritorial jurisdiction shall incorporate
features to accommodate all frequencies of rainfall events. In doing so, all design runoff
calculations of developed project land shall presume that the ground is saturated at the
beginning of the design storm.
Section 2. For purposes of calculating the runoff coefficient in accordance with
Section 5.1.3.1 of the City's SDDCM, the "Rational Method" shall be used, however all
developed "C" factors shall be increased by 5% (to a maximum of C=1.0). For example,
C-0.5 shall become C=0.53, rounded up from 0.525. For detention design purposes,
runoff of pre-developed project land shall presume dry land at the beginning of the design
storm.
Section 3. For purposes of determining detention basin volume in accordance
RESOLUTION NO. R2003-49
with Section 8.3 of the City's SDDCM, all detention designs shall be accepted as
conforming to the SDDCM if they include before and after discharge stage and flow
hydrographs of the 3-year, 10-year and 100 year-year rainfall events after improvements
that have peak flow and water level values that are equal to or less than pre-developed
peak values at any point in time.
Section 4. For purposes of meeting the requirement set forth in Section 8.6.5 of
the SDDCM, all detention basins must be designed to capture and hold the "first flush" of
surface pollutants that occurs at the start of the rainfall runoff. First Flush shall be defined
as equal to or greater that 0.5" of runoff from the entire acreage of the project land (0.042
acre/feet per acre).
PASSED, APPROVED and ADOPTED this the 10th day of Harch ,
A.D., 2003.
ATTEST:
(, N G L,~)~Ff'11qG,/T~I C/
SE(T, RETARY
APPROVED AS TO FORM:
DARRIN M. COKER
CItY ATTORNEY
TOM REID
MAYOR