Geology Reference
In-Depth Information
FIGURE 10.9
Location map and distribution of precipitation, in the mountains of the Big Thompson River Basin, July 31-August 2,
1976. Open and shaded triangles are discharge and precipitation sites; other precipitation sites represented by shaded circles.
Isohyets are in inches. Arrows by rivers indicate flow direction.
(Base map from McCain et al., 1979; isohyets modified from Shroba et al., 1979)
River between Estes Park and the mouth of Big
Thompson Canyon, 9 miles west of Loveland, Colorado
(Figure 10.9).
The storms developed when moist, conditionally
unstable air was pushed steadily westward up the
slopes of the Front Range. By 1830 MDT (6:30 PM
Mountain Daylight Time; times in this section are given
in a 24-hour system, as this is how they were originally
reported) a N-S line of strong thunderstorms had
developed on the foothills. These nearly stationary
storms intensified as additional low-level moist air
flowed westward from the plains. This system locally
released more than 7 in. of precipitation between 1930
and 2040 MDT, July 31. The high precipitation rate and
the steep terrain caused rapid surface runoff and the
Big Thompson River quickly reached flood stage.
