CAD-SketchUp contours

I don't know how many of you have used SketchUp for modeling, but here's a problem I'm facing:

I am a landscape architect. Our company is trying to use SketchUp to create models of a river alignment project we are working on. Currently, our method is to import the CAD contour lines into SketchUp and create a topography mesh to build our roads, pavilions, etc on top of.

The issue I'm encountering is that the contour lines we are getting from civil engineers and surveyors are exploded splines, so the polylines created have hundreds or thousands of vertices. This is an issue in SketchUp becuase that program creates 3-sided polygons to form a mesh, and the meshes right now contain upwards of 60,000 polygons. This means the model is huge and somewhat unstable and hard to work with.

I'm working on getting our boss to realize that this is not the best program for what we're trying to do, but in the meantime, does anyone know of a way to simplify the contour lines in CAD so there are fewer vertices? Short of re-drawing the lines individually (this is a 5-10 mile long section of river with at about 50 feet of grade change on either side of the river), I'm out of ideas.

I'd appreciate any help you guys can give me!