Assessment of the Alluvial Sediments in the Big Thompson River Valley, Colorado

The traveltimes were processed to estimate velocities and thicknesses for a layered-earth model; from these models, three cross sections of the river valley were constructed. The river valleys are covered by a layer of soil, which is 0.2 to 1.5 m thick.

Beneath the soil, there is one layer of alluvium at some locations and two layers at other locations. For the two westernmost cross sections, the total thickness of the alluvium ranges from about 6 to 10 m near the center of the valley and from about 2 to 6 m near the sides of the valley. The easternmost cross section is somewhat more complex than the other two, because it is near the confluence of the Big Thompson and the Little Thompson Rivers.