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Reece Fraser

Modelling a Spillway

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Hello all

We have constructed a 2D model of a town that has been flooded from the overtopping of a dam's spillway and have used multiple 2D domains for varying resolution of the flood processes & extents throughout various aspects of the town and to model differing features (i.e. finer grids around bridges etc).

We originally obtained the hydrograph at the crest of the spillway and input this as a QT boundary at the base of the spillway to avoid instability issues etc. However now we wish to be able to model

a) different water surface elevations in the dam

B) different dam configurations

c) different spillway configurations

... and their impacts on flood levels downstream in the town (approx 10km of model).

I was thinking that the best approach would be to place a QH boundary in the dam and use TUFLOW to calculate flows over the spillway and through the modifications. However as outlined in various sources, 2D models do not do well with steep gradients. Therefore, I was thinking that some approaches to model the spillway (and modifications) would be to

a) model the spillway as a 1D channel within the 2d model by carving out the spillway as a 1D domain;

B) model the spillway as a very 'high' box culvert (i.e. spillway width x 10m high) within the 2d model (i.e. a culvert with HX lines at the top and at the base);

c) create a separate grid, of finer resoltuion (i.e Dam is 50m resoltuion) with a higher timestep (i.e. 0.25sec) and embed this within the greater 2D model.

I was wondering what the best approach would be, and if anyone can think of any better approaches?



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