Learn how multiple drainage objects interact with one another on a surface.
This video demonstrates:
In most cases, you will need multiple drainage grading objects in your site. In Grading Optimization, grading objects adhere to a specific set of rules to prioritise conflicting slope goals. In some instances, an Exclusive Drainage Zone may override such conflicts.
In this example, we'll examine what the optimisation does for solving the slope direction in the case of two drain lines. Each surface triangle must redirect to only one drainage object.
When working with drainage with multiple drain lines, surface triangles prioritise their slope optimisation by proximity to drainage objects. This triangle determines the closest drain line and disregards the other. As a result, this is the slope direction of this triangle. Using this logic, the surface triangles know which object has priority over their slope optimisation.
Enable Hydrology Direction Vectors and Wireframe Topology on the Visualisation Toolbar to observe the intended inclination for each triangle in this project. Disable Hydrology, select Contour Topology and run the optimisation.
If you need to override drainage priorities in a project, you can use the Exclusive Drainage property of zones.
Consider the previous conceptual example with an additional low point object. These three triangles will slope towards the drain line as it is closer. The low point, however, is desired for drainage.
To fix this, a zone is needed to encompass the affected triangles and apply the Exclusive Drainage property to it. Surface triangles in this zone ignore drain objects outside the zone and only focus on drain objects within the zone. Surface triangles outside the zone can still recognise and respect drainage objects inside the zone.
As in our conceptual example, start by sketching a zone to isolate the surface triangles in the vicinity of the low point. Then select Exclusive Drainage in the Zone Properties dialog. Now when viewed in Wireframe mode with Hydrology Direction Vectors on, you can see how the triangles in the zone have changed direction. When optimised, the prioritisation of drainage is evident.
Using multiple drainage objects and Exclusive Drainage zones, you can plan for drainage patterns when optimising your project.