When planning a new site, all swales and overground flow paths should be fitted perpendicular to existing contours. See [[Natural drainage]] and [[Existing hydrology]].
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===Best cross sections===
===Best cross sections===
[[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]]