Assumptions

The following list is a summary of major assumptions used in the program. Other assumptions may apply to certain selected options as described in the implementation section.

  1. A uniform flow condition is assumed for calculating the spread in the gutter. Except for the flat bridge case, the spread at a profile slope less than 0.003 will be calculated using a profile slope equal to 0.003.
  2. Neglect the friction resistance at the vertical face of the curb.
  3. Neglect any local depression at the inlet.
  4. Assume the location of a slotted inlet at the gutter flow line.
  5. Assume that only one location between the previous inlet (or crest) and the low point will have a spread equal to the design spread.
  6. Three major assumptions are used in calculating the time of concentration at an inlet: uniform side inflow, constant cross slope, and by-pass flow is not considered in determining the time of concentration.
  7. Assume a vertical curve for the gutter line can be described by a second order curve, even at a superelevation transition section.