I found this
US Forest Service guide covering in detail the following bridge types (including CAD templates) very useful. No reason to reinvent the wheel.
We have a small stream in a valley we want to span and originally I was thinking a bridge, but realized everywhere close by the spanning of streams was done with causeways and culverts due to the silty/sandy soil. There are three ways to solve the issue, create a ford, add a causeway and culvert or add a bridge.
A resource I've also found useful for planning this sort of project is the
USGS National Map Viewer that allows you to overlay layers, adjust order and transparency to see pretty detailed Lidar images of your project. This shows the use of a measurement tool showing the area off a potential causeway overlaid on lidar layers, "hillside stretched" and contour lines which for our area are very accurate in our area, though the wetlands data seems offset from the lidar data, though accurate in the aggregate AFAICT, just annoyingly mis-aligned.
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