Survey Data 
114. Waves and currents interacting with bottom sediments produce 
changes in the beach and nearshore bathymetry. These changes can occur very 
rapidly in response to storms or slowly as a result of persistent but lower 
seasonal variations in wave and current conditions. 
115. To document the temporal and spatial variability in bathymetry, 
surveys were conducted approximately monthly of an area extending 600 m north 
and south of the pier and approximately 950 m offshore. During March and 
July, 24 profile lines were surveyed. The remaining surveys consist of 
between 12 and 15 profiles each. These profiles were obtained using a Zeiss 
Elta-2 first-order, self-recording electronic theodolite distance meter in 
combination with the CRAB, a 10.7-m-high self-powered mobile tripod on wheels 
(Birkemeier and Mason 1984). In addition, soundings were taken on both the 
north and south sides of the pier. 
116. In the following sections a brief discussion of the effect of the 
research pier on the bathymetry precedes discussions of time-histories of bot- 
tom elevations at selected locations along the pier and contour diagrams of 
the bathymetry. 
Pier effect 
117. The research pier introduces a perturbation in bathymetry (Fig- 
ure 38) in the form of a permanent trough under the pier, apparently a result 
of the interaction of waves and currents with the pilings. The trough deepens 
under the seaward end of the pier and varies in shape and depth with changing 
wave and current conditions. The pier's effect on shore-parallel contours 
occurs as far as 300 m away, and the shoreline may be affected up to 350 m 
from the pier (Miller, Birkemeier, and DeWall 1983). 
History of bottom elevation 
118. At the Baylor wave gage locations and other selected locations 
along the pier, a history of the bottom elevations is useful for interpreta- 
tion of the data (Figure 39). Variations of elevation under the pier are due 
to natural processes (such as profile changes due to bar movement) as well as 
scour due to the interaction of the pier piles with waves and currents. At 
the beginning of the year, the scour hole at the 579-m location was 8-1/2 m 
deep and the trough elongated to the north. A small fillet (at -1 m) formed 
at the landward end of the pier, near 189 m, during February. The fillet 
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