Dam Spillway

Flexible Design With Powerful Runoff Velocity Analysis

Location: Queensland, Australia
Field Area: 50 acres or 20 hectares
Irrigation Method: n/a
Crops: n/a

Figure 1. Proposed Runoff Analysis simulated over the Proposed Topography in 3D View.


The spillway for the dam is having problems discharging to a nearby gully without eroding. The spillway needs to be redesigned to prevent high runoff velocities which are causing erosion issues.

The Runoff Analysis over the Existing Topography below shows areas of high velocity and runoff depth.

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Figure 2. Existing Topography (left) and Existing Runoff Analysis (right) of the Spillway. Drag the slider left or right to view each.


The peak discharge was calculated for a 100-yr storm event using engineering hydrology for the catchment further upstream and was determined to be 120 m3/s.

This calls for a spillway of 220m or 660ft wide at the entrance of the spillway and we've tapered it down to the gully. The spillway was designed by manually drawing breaklines to produce the base and the levees.

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Figure 3. Existing Topography (left) and Proposed Topography (right). Drag the slider left or right to view each.

The Runoff Analysis was run over the Proposed Topography showing reduced velocities and runoff depth.

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Figure 4. Proposed Topography (left) and Proposed Runoff Analysis (right). Drag the slider left or right to view each.

Figure 5. Spillway Long Section.

Figure 6. Proposed Cut/Fill Map.


No other software gives you the ease and flexibility of designing erosion control structures like this. However, a unique super power of OptiSurface is the runoff velocities and depth can be simulated over the proposed design.

Video Explanation

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