Internal validation of the drainage scheme
MIKE SHE performs an internal validation of the SZ drainage scheme. The following are used in connection with the sub-scale feature:
Drainage depths of zero
Zero depths are allowed and drainage depths above the topography are set to the topography. This allows drain levels at the ground surface. This check will be done on the coarse grid. That is, if the coarse grid drain level is above the coarse grid topography, a warning will be issued and all the sub-grid drain depths will be set to zero.
Note for Release 2011 In Release 2011 and prior releases, a drain level of zero turned off SZ drainage, and drain levels above topography were set to the topography (and turned off drainage). For backwards compatibility an Extra Parameter is available.
|
Parameter Name |
Type |
Value |
|---|---|---|
|
disable drains at or above ground |
Boolean |
On |
Drain levels vs River link elevations
There is an optional Extra Parameter check in the drainage routing by levels that checks on the river link bottom elevation.
|
Parameter Name |
Type |
Value |
|---|---|---|
|
check drain level against bed level |
Boolean |
On |
If the river link bottom elevation is higher than the drain level, the cell becomes a local depression. However, this will likely create a lot of local depressions beside the rivers.
When using the multi-grid OL option, the drainage in a coarse cell is controlled by the minimum drainage level in the cell. If one sub-grid cell has a drainage level below the bed level then the drainage in the entire cell is transferred to an internal depression.
Note for Release 2011 The check was originally added to prevent the "lifting" of drainage water up to a river link. However, in most cases, such lifting is probably unintentional. That is, the river bed has been poorly interpolated. Prior to Release 2012, this was the default behaviour and the check above has been added for backwards compatibility.
There is a check on the drain levels below the bottom of the model. If the coarse grid drain level is below the coarse grid bottom of the model, then a warning will be printed and the drain level will be adjusted to the bottom of the model. In the sub-grids, you may have the situation where the sub-grid drain level is below the bottom of the model, but the average drain level is above. In this case, the sub-grid drain level will be the maximum elevation of the bottom of the model and the drain level. Meaning if the drain level of a sub-grid is below the bottom of the model, the drain level is adjusted to the maximum value of i) the bottom of the model and ii) the drainage elevation.
