Civil 3D cheerfully inverted my 0.5% fall on the rain garden and generated contours that send stormwater majestically onto the plaza on L3.2. Is there a hidden checkbox for “respect gravity” or do my slope arrows just prefer irrigating café seating over the bioswale?
Been burned by the 0.5% too — my fix is to draw a feature line down the bioswale centerline, lock the downstream node to a hard low elevation, and add that as a Standard breakline at the very top of the surface definition so rebuilds can’t undo “respect gravity.” If you’re seeing water head for L3.2 café seating, check that contours aren’t being smoothed after the breakline; even light smoothing will crown that tiny fall. Do you have that feature line above the corridor/contours in the build order, or is it coming in after?
On those 0.5% swales, I’ve had luck going Surface > Edits > Swap Edge and flipping the TIN along the bioswale/plaza seam so the triangle flow points into the swale; it’s the quickest way I’ve found to make the contours on L3.2 “respect gravity.” If it holds, toggle Use Maximum Triangle Length so a rebuild doesn’t stretch a rogue triangle back toward the café: https://help.autodesk.com/view/CIV3D/ENU/.