Bathymetry of Cannikin Lake, Amchitka Island, Alaska, with

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COMPUIXR CALCULATION OF CUMWIATIVE VOLUME A plot tape produced ueing the WET program contained an array of values giving the x and y coordLnates and the calculated elevation of the lake bottom at regularly-spaced distances over an area covering the entire lab. This array was used to calculate the volume of water in the lake for any desired water elevation uming the following procedure: Plot the array of x and y coordinates covering the lake. The distance between two adjacent pointm with the same y coordinate is Ax. The distance between two adjacent pointa with the same x coordinate in Ay. In the WET program. Ax and Ay were equal, thus the distance between parallel x or y coordinates i8 equal and is called Ad. As 8tated previously, a calculated altitude of the lake bottom is associated with each point (x and y coordinate). Aaaume that thin altitude L is constant for a square of area ( hd) in which the point (x,y coordinate) is located at the center of the square. The volume of the lake can be calculated by subtracting the calcuhtcd altitude of the lake bottom at each applicable point from the given water-level altitude, multiplying this difference by ( ~d)*, and su~ng this remult for all applicable points. An applicable point would be we for which the calculated altitude of the Lake bottom wan lower than the given water-lmel altitude. The array from the WET program plot tape was read in as input to part of the WET computer program which scanned the calculated altitude values of the lake bottom and noted and stored each different altitude value. These altitude values were then sorted in ascending order and used as given water- level altitudes to calculate the volume of the lake using the method described above. These water-level altitudes versus volumetric results are shown as the stagevolume relationehip for Cannikfn Lake in figure 3. 15 - -
OBLIQUE PROJECTIONS The result of using the oblique-projection option in the WET program is shown in figure 6 and is typical of the type of representations produced. The oblique projections of the lake bottom are viewed downstream toward the intersection of the northeast-trending fault and White Alice Creek. Variations in perspective may be obtained by varying the x-y-z vfewing coordinates. A pictorial view may be obtained and St is possible co produce views of the lake bottom as would be seen from above or below shoreline datum by using various shading techniques as those shown on figure 7. These figures are often helpful in visualizing features displayed on the computer-produced plarrimetric contour maps. A change in the viewing position allowe one to view certain pertinent feature6 along a favorable line of sight. SIMMARY The detonation of the Cannikin nuclear explosion and subaequent collapee in the area has created Amchitka's most outstanding lake. The manually-drawn bathymetric map (fig. 3), based on data from a monic survey made of the lake, is the standard of comparison for two additional bathymetric maps produced from two computer-mapping programs using the same data. These are the WET program and the Calcomp GPCP program. The com- parisons show tht the Calcomp program, with proper selection of neighbor- hood and grid uize, can produce a map that compares very well with the hand-drawn standard. - \
Page 2 and 3: . . , . . - . . ted Copj
Page 4 and 5: CONTENTS Page Abstract. . . . . . .
Page 6 and 7: This figure is not available in ele
Page 8 and 9: UNITIDJ STATES Amchitka-41 DEPARTME
Page 10: cavity-radii from the point of the
Page 13 and 14: The average annual precipitation is
Page 15 and 16: .> BATHYMETRY The bathymetric map o
Page 17 and 18: WET computer program ate selecced r
Page 19 and 20: .... firer operation determinee the
Page 21: The middle part of the lake also la
Page 25 and 26: Figure 6-- Oblique projection, Conn
Page 27 and 28: REFERENCES CITED Calcomp, 1971, A g
Page 29 and 30: Loa 4lamos Scientific Laboratory, L
Page 31: .- * U.S. Army Corpe of En~ineers,

Bathymetry of Cannikin Lake, Amchitka Island, Alaska, with

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