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Line 14:
Line 14: − + − + − + − * Triangle (a), wetted perimeter at full bank depth = 8.25 (unitless)+ − * Trapezoidal (b), wetted perimeter at full bank depth = 8.32 (unitless) − Where the X-section areas are set equal (to demonstrate equivalent flow), the depth of water in the example trapzoidal channel is 4/5 that of the triangular.
→Planning considerations
==Planning considerations==
==Planning considerations==
<h3>Best X-section</h3>
<h3>Best cross sections</h3>
[[File:Best X-section.png|thumb|Both sections a)triangular and, b)trapezoidal, are constrained within ratios of 8:1 H:V]]
[[File:Best X-section.png|thumb|Both sections a)triangular and, b)trapezoidal, are constrained within ratios of 8:1 H:V]]
Enhanced swales aim to both reduce the flow rate and retain a portion of the conveyed water. For these purposes the best X-section is that which maximizes the wetted perimeter. The trapzoidal channel has the marginally greater hydraulic radius, but also the greater area.
[[File:Sections_perimeters.png|thumb|At lowest flow rates (smallest area) the trapezoidal swale (b) has the greater wetted perimeter, at higher flow rates (greater area) the triangular geometry (a)has a larger wetted perimeter for same area. Both channels modelled using ratios shown in figure above]]
Enhanced swales aim to both reduce the flow rate and retain a portion of the conveyed water. For these purposes the best x-section is that which maximizes the wetted perimeter for a given area.
===Check dams===
===Check dams===