Any downstream capacity hydraulic analysis conducted in accordance
with this Chapter shall use the following criteria for determining
adequacy for accepting increased peak flow rates:
A. Natural or man-made channels or swales must be able to convey the
increased runoff associated with a twenty-five-year return period
event within their banks at velocities consistent with protection
of the channels from erosion. Acceptable velocities shall be based
upon criteria included in the PADEP Erosion and Sediment Pollution
Control Program Manual.
B. Natural or man-made channels or swales must be able to convey the
increased twenty-five-year return period runoff without creating any
hazard to persons or property.
C. Culverts, bridges, storm sewers, or any other facilities which must
pass or convey flows from the tributary area must be designed in accordance
with PADEP Chapter 105 regulations (if applicable) and, at a minimum,
pass the increased twenty-five-year return period runoff, except for
facilities located within a designated floodplain area which must,
at a minimum, conform to FEMA and local floodplain ordinance requirements.