Figure 9.4. Washita River, north of Maysville, Oklahoma (Example 3).
9.5.4 Beaver River, North of Laverne, Oklahoma (Example 4)
During high flows of 1938, the river washed over the south bank and damaged the approach
roadway south of the bridge. The south end of the bridge was also damaged. Jetty fields
were constructed in several locations upstream of the bridge in an attempt to reduce bank
erosion. Two jetty lines were constructed in a side channel downstream of the bridge to
discourage flow in that channel to prevent eddy currents from eroding the north embankment
(Figure 9.5a). A new longer bridge was constructed in 194l. High flows in 1946 caused
severe erosion on the south bank upstream from the bridge. In 1949, an earth dike and jetty
field were constructed on the south bank to prevent further erosion. In 1969, the river cut
through a portion of the 1949 jetty field and eroded the earth dike (Figure. 9.5b). Car bodies
were used as bank protection. However, car bodies are not environmentally acceptable and
are difficult to hold in place unless anchored with cable or weighted down with concrete or
rocks.
9.5.5 Powder River, 40 Miles East of Buffalo, Wyoming (Example 5)
The Powder River has very fine bed material and a high sinuosity. The river contains dunes
and antidunes at low flows. At the bridge site, there was a grove of cottonwood trees on the
upstream east bank of the bridge and a dry draw coming in from the upstream left bank
(Figure 9.6a). Upon completion of the bridge, a large flood occurred. The river attempted to
straighten out its meanders possibly as a result of instream or floodplain mining in conjunction
with the road construction. At the same time, the draw on the upstream left bank was
bringing in a large amount of sediment, forcing the stream toward the upstream side of the
(east) abutment. The flood flow uprooted the grove of cottonwoods which impacted on the
sacked concrete riprapped spur dike (guide bank) at the east abutment and destroyed the
dike (Figure 9.6b). To restore the channel to its original alignment, a training dike was
constructed from the bridge upstream to a nearby bluff (Figure 9.6c). A jack jetty field was
also constructed on the upstream meander to prevent the river from flowing across the point
bar. The jetty field has begun to fail as a result of the streamside piles being undercut. The
streamside anchors were rebuilt by driving the piles deeper in the center of small riprapped
mounds.
9.23
Previous Page
