Use the Flow Path Vista to edit flow segment data and to add flow segments of the type required for the catchment area.
Specifies the reference surface on which to base the flow path slopes. Slopes for all segments are based on a single surface. When you change the reference surface to another surface, the slope fields are updated. If you change the reference surface from an existing surface to <none>, the slope fields become active so you can edit the slopes, but the existing values in those fields remain unchanged.
Specifies the flow segment type. The SCS flow types are available if the Time of Concentration method for the flow path is set to TR-55.
Sheet flow is a very shallow flow over plane surfaces. It is the first component of Tc and starts at the hydraulically most distant watershed point. Sheet flow normally occurs at a depth of 0.1 ft. or less, and the length of sheet flow rarely exceeds a few hundred feet. The maximum length of sheet flow is 300 ft. Data used to compute the sheet flow are the length of flow, the slope, the 2-year 24-hour rainfall amount, and the ground roughness as measured by Manning's n.
Shallow concentrated flow type normally occurs after a maximum of 300 feet of sheet flow. The average velocity of shallow concentrated flow is determined by watershed slope and channel material (paved or unpaved). Typical areas where shallow flow occurs are in swales between houses and the gutter section of a roadway.
Channel flow type begins where surveyed channel cross section information has been obtained, where channels are visible on aerial photographs, or where streams are indicated on USGS quadrangle sheets.
Specifies the 2 year, 24-hour rainfall intensity value for the catchment area. This value is used in the TR-55 Time of Concentration equation to calculate the sheet flow travel time.
Specifies the surface type over which the shallow concentrated flow travels.
Specifies the cross-sectional area for the open channel. This is the channel cross sectional area for bank-full conditions (when the channel is filled to the bank). This value is used as input in the TR-55 Time of Concentration equation to calculate the channel flow travel time.
Specifies the wetted perimeter for the open channel. In cross section view, a channel has an approximate U-shape. The wetted perimeter is the length of this "U." This value is used as input in the TR-55 Time of Concentration equation to calculate the channel flow travel time.