Lava Barrier at Hilo— WENTWORTH, POWERS, and EATON 
357 
carry the load at 60 yd/hr velocity. Assuming 
an average depth of 20 yd., the width of channel 
required is about 1,700 yd. ( 1 mi.) and the up- 
slope would exceed 200 ft. 
These ' examples have neglected the overde- 
sign necessary to accommodate the transporta- 
tion of distributary flows. 
CHANGING THE MOVEMENT PATTERN OF 
LAVA FLOWS BY BOMBING 
It has long been understood by observers of 
Hawaiian lava flows that the course and progress 
of a flow can be radically altered by breaching 
the levee bank of the main feeding channel. 
Macdonald (1958) presents an excellent discus- 
sion and evaluation of the matter which need 
not be repeated here. He concludes that efforts 
to divert the flows by bombing should be made 
in the event of a threat to Hilo, but that a bar- 
rier system also should be constructed as insur- 
ance against failure of the bombing effort, par- 
ticularly in the event that a voluminous, fast 
moving flow would overrun the area before 
bombing could be carried out. However, it 
would seem from the discussion in previous par- 
agraphs that an artificial diversion system of 
dimensions adequate to cope with a voluminous, 
fast moving flow would be expensive beyond 
prudent economic justification. Thus, it would 
seem that the hazard of being overrun by lava 
is one that must be accepted and lived with, 
perhaps analogous to the acceptance of earth- 
quake harzards by Tokyo and cities in other 
earthquake areas. 
REFERENCES 
Finch, R. H. 1925. Expedition to the southwest 
rift of Mauna Loa. Hawaii. Vole. Obs. Bull. 
13: 89-9E 
Finch, R. H., and G. A. Macdonald. 1953. 
Hawaiian volcanoes during 1950: The 1950 
eruption of Mauna Loa. U. S. Geol. Surv. Bull. 
99'6-B: 49-81. Hawaiian Volcano Observa- 
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Monthly Bull. 14 (14): 31-50. 
Hitchcock, C. H. 1909. Hawaii and Its Vol- 
canoes. The Hawaiian Gazette Co., Ltd., Ho- 
nolulu. 306 pp. 
Macdonald, G. A. 1941. Lava flows in eastern 
Puna. Volcano Lett. no. 474: 1-3. 
1958. Barriers to protect Hilo from lava 
flows. Pacif. Sci. 12(3): 258-277. 
Macdonald, G. A., and J. P. Eaton. 1954. 
The eruption of Kilauea volcano in May 
1954. Volcano Lett. no. 524: 1-9. 
Stearns, H. T., and G. A. Macdonald. 1946. 
Geology and ground-water resources of the 
island of Hawaii. Hawaii Div. Hydrogr. Bull. 
9, 363 pp. 
Wentworth, C. K. 1954. The physical be- 
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425-438. 
Wester velt, W. D. 1916. Hawaiian Legends 
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