The Crest-Stage Gage is a device for obtaining
the elevation of the flood crest of streams. The
gage is widely used because it is simple,
economical, reliable and easily installed.
Many different types of crest-stage gages have
been tested by the Geological Survey. The one found
most satisfactory is a vertical piece of 2 inch
galvanized pipe with a wood staff held in a fixed
position with relation to a datum reference. The
bottom cap has six intake holes located so as to
keep the non-hydrostatic drawdown or superelevation
inside the pipe to a minimum. Tests have shown this
arrangement of intake holes to be effective with
velocities up to 10 feet per second, and at angles
up to 30 degrees with the direction of flow. The top
cap contains one small vent hole.
The bottom cap contains regranulated cork. As the
water rises inside the pipe the cork floats on its
surface. When the water reaches its peak and starts
to recede, the cork adheres to the staff inside the
pipe, thereby retaining the crest stage of the
flood. The gage height of a peak is obtained by
measuring the interval on the staff between the
reference point and the floodmark.
While the standard gage is four feet in length,
other lengths are also available. The Type C gage is
mounted on a steel 2" pipe driven into the ground or
attached to a fence post.
Finely grounded cork for
crest-stage gages, 1 pound container |
Type A: Galvanized steel 4' long (other
lengths available) for mounting on a flat surface
with brackets.
Type C: Galvanized steel 4' long for
mounting on top of a steel pipe.
Type AP: Same as Type A in PVC material.
Type CP: Same as Type C in PVC material.
Granulated Cork: 1 pound box.
801-150 Type A Crest Gage 12 lbs.
801-160 Type C Crest Gage 12 lbs.
801-170 Type AP Crest Gage 5 lbs.
801-180 Type CP Crest Gage 5 lbs.
801-190 Granulated Cork 2 lbs.
The galvanized steel bracket is used to support
the gage and affix it to the mounting surface with
two 7/16 inch diameter holes. A minimum of 2
brackets are required to adequately support a
crest-stage gage.
801-195 6" Bracket 2 lbs.
801-196 8" Bracket 2.5 lbs.
801-197 10" Bracket 3 lbs.
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