The following definitions of terms apply to the minimum drainage requirements contained in this chapter:
"Flood hazard"
means overflow water having sufficient velocity to transport or deposit debris, to scour the surface soil, to lodge or damage buildings or to cause erosion of the banks of channels.
"Inundation"
indicates ponded water or water in motion of sufficient depth to damage property due to the mere presence of said water or deposition of silt.
"Major drainage channels or conduits"
means those channels or conduits which have a large drainage area and are under the jurisdiction of the Alameda County Flood Control and Water Conservation District.
"Minor drainage channels or conduits"
means those channels or conduits having a drainage area of fifty acres or less.
"Ponding of local storm water"
means standing of water in local depressions. As distinguished from "sheet overflow" this water originates on or in the vicinity of the property and due to the condition of the ground surface is unable to reach a drainage channel or conduit.
"Possible flood hazard"
means possible extension of areas denoted as subject to flood hazard and reflects the uncertainty of degree or extent of bank erosion.
"Secondary drainage channels or conduits"
means those channels or conduits which have a drainage area of more than fifty acres.
"Sheet overflow"
means water of minor depths either quiescent or flowing at velocities less than those necessary to produce serious scour.
(Ord. 143-76 § 2, 1976)
Runoff design shall be made for the frequency of occurrence hereinafter duplicated in these standards of modified rational method using basic data in accordance with the requirements set forth in the specifications. Runoff design shall accommodate the full and anticipated future development within the drainage area. In cases where such drainage areas are undeveloped, fully improved conditions shall be determined by conditions foreseen by the General Plan of the City for future development and by the Zoning Ordinance (Title 18) of the jurisdiction within which such areas are located. Any outlet channel required to carry storm water from the proposed subdivision to a defined drainage channel or conduit shall be adequate in accordance with these standards for the ultimate state of development in the drainage area resulting from the particular subdivision.
(Ord. 143-76 § 2, 1976)
Drainage channels and conduits directly affecting the proposed subdivision shall have the following minimum capacities:
A. 
Secondary drainage channels and conduits shall have capacity designed on a fifteen-year frequency of occurrence runoff.
B. 
Minor drainage channels, conduits, and appurtenant facilities shall have sufficient capacity to contain a ten-year frequency of occurrence runoff, including undefined or sheet overflow originating within the tract or adjacent thereto.
(Ord. 143-76 § 2, 1976)
Storm water within street areas shall be placed in closed conduits when the maximum depth of in-gutter runoff computed in accordance with the provisions of the Supplemental Design Standards exceeds five inches at the gutter.
Where improvement of a drainage channel or conduit which serves a larger area is necessitated by the development of a subdivision, the improvement may be accomplished through participation of all property benefiting. Such improvements may be accomplished through any acceptable means of financing which guarantees the accomplishment of the improvements to the satisfaction of the City Engineer.
(Ord. 143-76 § 2, 1976)
Drainage structures shall account for tidal action where applicable, and drainage shall be accomplished by gravity without surcharge in catch basins or manholes except by design.
(Ord. 143-76 § 2, 1976)
Catch basins shall have curb inlets of varying lengths so designed that the water is diverted into the catch basin without a reversal of direction of the flow of the water. The inlets shall be designed by the methods of the United States Bureau of Public Roads or by a like method using equivalent data.
(Ord. 143-76 § 2, 1976)