How to investigate increasing water levels in waterways
When using the Water Overlay, water should generally be in balance. Extraordinary events such as breaches or excessive rainfall may cause an excess of water to be added to (and possibly remain in) the model. But in general, and especially in stationary calculations, you would expect the amount of water flowing into the model to roughly balance the amount of water being removed from the water as well.
How to check whether water levels rise
You may be able to see visually on the overlay where potential issues exist, but by placing a measurement in the waterway you will be able to see more accurately whether the water level rises excessively over time.
- Ensure the Water Overlay has a surface last value result type.
- Open the measuring tool.
- Create a point measurement, in the location where you suspect the water level rises.
- Set the primary overlay to surface last value.
- Set the measurement graph display mode to "fit to graph".
- You now see the water level in that location in the waterway, across all timeframes of the simulation.
See if the resulting line is relatively flat, which would indicate that water remains more or less balanced. It's natural for the water level to be influences by temporary factors, so the water level going up and down during the simulation is fine. However, if the overal trent is for the water to keep rising, there may be an issue.
What can you look for when a flow issue occurs
Because water can flow in and out of any location through a number of routes and have varying origins, it can be quite challenging to find the root cause of the increase of the water (if there even is a single cause). However, a number of avenues of investigation are relevant.
Is there any excessive input?
Rainfall, inlets, pumps inundation area
Is the location a bottleneck?
Terrein height a valley No (or incorrectly configured) output constructions Any flow issues
Is there an edge of the calculation model nearby?
- Check what the current grid cell size is, and check whether the issue occurs near the edge of the project area. Note that the outer two cells of the project area are not part of the calculation.
- Check whether the location of the issue is inside the designated calculation area. You can do so at the weather event step in the configuration wizard, where you can check the configuration for the calculation area. If it is set to water level areas only, check whether the location of the issue is covered by a water level area. If it is set to specified areas only, check whether the location of the issue is covered by a limit area.
- Check whether the issue takes place near the the edge of the calculation area. The closer to the edge a calculation takes place, the more chance there is of unintended edge effects.