Feasibility of a Lava-diverting Barrier at Hilo, H awaii!

THE SUBJECT of the value and possibility of protecting H ilo Harbor and vicinity from de-vastation by a lava flow from Mauna Loa is again being given thoughtful consideration by the residents of Hawaii. Those who must weigh the pros and cons of this matt er need informa-tion, p art of which can best be appraised by geologists and engineers. From the geologists' appraisal should come answers to questions such as the following: How often might protection from a lava flow be needed? Is it physically possible to divert a lava flow with a man-made structur e? What are the necessary dimensions of such a structure? Of what should it be built? What is its expected useful life? Various references to COSt have been made. Some say that a barri er is justified, regardless of cost; others hold to a strict account ing of sup-posed risk againstcost, amortiz ation, and other factors. Th ese opposed views are widely sep-arated. Many risks could be reduced by astro-nomical spend ing, but such spending may be beyond reasonable relation to contemporary life or even to capacity of the community to pay. Though opinions may differ greatly, the cri te-rion of economic justification cannot be ignored altogether. Much has been written on the subject of a lava barri er for H ilo. The latest and most com-prehensive review and discussion is by Gordon A. Macdonald ( 1958). His greatest emphas is is laid on the matter of a barrier system to be con-structed across the slope above Hilo to divert the course of an approaching lava flow. He con-cludes that a system of barriers can divert the course of a lava flow. Th e conclusions reached in this report differ in this matt er from those expressed by Mac-donald because different evaluations are made of the same few facts available for appraisal. 1 Publ ication authorized by the Director, U. S. Geo