tidal boundary where beach is not parallel to DEM edge

[Will]

Hello,

Is there guidance on how to best represent a tidal condition given:

• a long barrier beach that is not parallel to a DEM edge
• one low-flow river opening

Ideally, I would set a linear boundary along the beach, but tidal control in CAESAR appears to be a rectangle that is orthogonal to the raster/DEM axes.

I've tried two approaches for defining the tidal coordinates (on hydrology tab):

1) by the endpoints on the beach

• where stormflow could potentially overtop 
• however, this enforces the tidal interface well up into the estuary

2) in the vicinity of the river mouth only, 

• with one edge extending to the edge of the raster
• however, this creates two large ocean 'void' that needs to be filled during warmup
• I am doing a 24 hr warmup 

I have not tried transforming/rotating the DEM. I would like to avoid this if possible.

Cheers,

Will

PS. I would have uploaded an image, but it seems I don't have permission.

[Tom Coulthard]

Hi Will - theres not a simple answer I'm afraid apart from Rotating your grid. OR its worth considering that the tidal input will set ALL water elevations within the rectangle to the same water depth - so if (for example) you have an inlet (lets say river comes into sea from top left to bottom right) that is diagonal but only fully submerged at high tide (or mostly submerged) then you could specify an over large box/rectangle on the bottom right side... if that makes sense. 

Otherwise its re-write some of the code (probably not too hard if you want to do that) or transform the DEM - which I agree is something to be avoided if possible. 

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[Will]

Hello, Tom. Cheers for the reply. 

I'd be game to contribute to the code, but never having written C# makes it a bit of a barrier I'm afraid. 

The "over-large" rectangle you note sounds similar to my approach #1. My approach #2 produces interesting results as well. I'm not entirely convinced of the believability of either though.

My specific area of interest is upstream of the coast a wee ways, but still tidally affected. I will try an ensemble approach using tidally-influenced stage outputs from a hydrodynamic model as the CL tidal control in a location that better aligns with the DEM edge.

Thank-you again.

Kind regards,

Will