How to investigate flow issues in waterways

This article is a stub.

When using the Water Overlay, water should usually be able to flow freely through waterways. For some situation, it may be evident that water should not be able to flow further, such as at a properly configured weir or pump, or when the bottom of the waterway rises or has an obvious bump.

How to check whether water flows properly

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 how much water is where in the waterway.

How to check whether water flows properly through a waterway:

1. Ensure the Water Overlay has a surface last value result type and a surface elevation.
2. Open the measuring tool.
3. Create a line measurement, with one endpoint at the start of the waterway, and the other endpoint at the end of the waterway.
4. Set the primary overlay to surface last value, the base overlay to surface elevation, and activate "sum".
5. Set the measurement graph display mode to "fit to graph".
6. You now see the water level across the length of the waterway.

See if the resulting summed line is (nearly) flat, or if there is a point where the water level suddenly jumps to a different level.

What can you look for when a flow issue occurs

Because inhibited waterflow can have a number of causes, there isn't a single fix for all situations. Check whether any of the following apply to your situation, and interpret in the context of your own use-case what the desirable solution would be.

Is the surface elevation in that location what you expect?

• In the relevant waterway, use the measurement made earlier to see whether the height of the bottom of the waterway is as shallow or as deep as you expect.
• Also check whether the height of the terrain is consistent, or inclined, and whether the height of the terrain exceeds the height of the water at any point.

Is there a construction in the waterway which causes a blockage?

• Activate the water overlay and see whether there is a construction in that location. See if there is a weir or a pump with an angle configured. You can tell by the dam visualized in that location. If so, inspect that construction to see how and when water can flow past it, and how much.
• Also see if there is an inlet, pump, or overflow in that location. It's possible water is added in that location and just flows off in one direction, or that in that location water is removed at such a rate that it doesn't reach the other side of the waterway.

Is there a hydrological feature nearby which blocks the waterway?

• If available, use the base types result type to inspect the location and see whether cells are marked as breach, or as outside of calculation area, or otherwise inconsistently with the rest of the waterway.