HR: 1330h
AN: H52A-1142    [PDF]
TI: Quantifying the Convexity of Waterfalls Along the Niobrara River, Cherry, Keya Paha, and Brown Counties, Nebraska
AU: * Mason, L J
EM: lmason2@bigred.unl.edu
AF: Univ. of Nebraska-Lincoln, 214 Bessey Hall Dept. of Geosciences Univ. of Nebraska-Lincoln, Lincoln, NE 68588-0340 United States
AU: Pederson, D T
EM: dpederson2@unl.edu
AF: Univ. of Nebraska-Lincoln, 214 Bessey Hall Dept. of Geosciences Univ. of Nebraska-Lincoln, Lincoln, NE 68588-0340 United States
AU: Goble, R J
EM: rgoble2@unl.edu
AF: Univ. of Nebraska-Lincoln, 214 Bessey Hall Dept. of Geosciences Univ. of Nebraska-Lincoln, Lincoln, NE 68588-0340 United States
AB: Numerous waterfalls are present along the spring branch canyons of the Niobrara River, downstream of Cornell Dam, Valentine, Nebraska. Although the sizes of the waterfalls are variable, a majority of the waterfall faces have a convex outward geometry. In order to gain a better understanding of the processes responsible for the development of this profile, it is useful to quantify the convexity of the waterfall face. Due to the rugged topography of the spring branch canyon environment, traditional techniques, such as pin-flag and tape measurements are not practical and even dangerous. The waterfall faces are often greater than 3 meters high, steep, and algae covered. The spring branch canyon walls are also steep with actively creeping scree slopes along the bases. Therefore, due to this topography there is no easy way to access the waterfall faces for accurate measurements. The measurement problem was overcome by using a hand-held laser meter mounted on a tripod. A baseline was established below the waterfall face. The length of the baseline was measured using the hand-held laser meter. Measurements were taken on distinct features across the waterfall face and sidewalls from both endpoints of the baseline. The angle of the laser off the baseline and off the horizontal were measured using a compass with mirror. With these measurements, the waterfall faces profile relative to the baseline was reconstructed. A hand-held laser meter is an important tool for measuring waterfalls and other geomorphic features in hazardous environments because measurements can be taken from a safe location. It is possible for one person to take accurate measurements. New baselines can readily be established to measure relative erosion along the waterfall face over time.
DE: 1815 Erosion and sedimentation
DE: 1824 Geomorphology (1625)
DE: 1886 Weathering (1625)
DE: 1894 Instruments and techniques
SC: Hydrology [H]
MN: 2003 Fall Meeting