Drainage datum (Water Overlay)
|DRAINAGE_DATUM||datum||The datum height of the drainage.||n/a|
Water can be drained out of the underground when it exceeds the drainage's datum height. Water in the underground lower than the drainage is out of reach, and cannot flow through the drainage.
- The drainage height should be higher than the bottom of the waterway it drains water to.
- If no height is defined, the drainage is considered to be low enough for all groundwater to flow into the waterway.
- If no height attribute is defined, a DRAINAGE_OVERFLOW_THRESHOLD must be defined, otherwise the assumed low positioning of the drainage will prohibit surface water from flowing in or out.
- This means that the height attribute is required when using passive drainage, otherwise water will never be able to flow through to the drainage laying far below the surface.