Lava did cut off the tributaries to the Wailuku River. Then, the hot rock flow stopped a mile away from the town center of Hilo.
However, in 1970, cannons of frigid sea water were used on the Icelandic island of Haimey, and saved part of the town of Vestmannaeyjar and its harbor:
One and a half billion gallons of water were used over a period of 5 months, and that scene above is where the lava flow actually stopped.
chemical engineering solution would be to introduce carbonate rocks (such as limestone). There would be an endothermic reaction to cool the lava, increasing the viscosity and stopping the flow. Unfortunately, if the volcano keeps spewing out molten rock, the flow could go elsewhere, and there would be liability problems. Similarly, a barrier can be used, and, if it works, will only pass on the problem to your neighbor. Here is a dike solution (right) applied in Japan, but this was for volcanic mudflow, not lava.
Madame Pele (painting by Herb Kane) became responsible for the demise of geothermal power in Hawaii. The potential could well be 500 MW of cost effective and base load power. In the 70's, Hawaiian protesters warned that she would get angry, Federal Judge David Ezra agreed that there was insufficient environmental data, thus effectively limiting the spread of this power potential for the Big Island.
777 homes for sale in Pahoa. While not exactly under similar circumstances, I can sympathize with these owners, for my apartment is now for sale in Honolulu. The human toll and assorted humanitarian tragedies in Puna cannot be discounted if the worst happens, but there is only one geothermal facility in Hawaii, and I helped build it. Life is full of contradictions and conflicts.
Super Typhoon Nuri is already at 150 MPH and will further strengthen into a Category 5:
However, computer models continue to show Nuri tracking a path in the Pacific Ocean sufficiently east of Japan. Big waves can be predicted for the north shore of Hawaii in ten days or so.
There is a second ocean storm, in the East Pacific. Hurricane Vance, at 80 MPH, will strengthen into a Category 2:
While originally projected to crash into the main part of Mexico, current models show Vance making some complicated moves, maybe even passing west of Baha:
Cruise ships in that region will have problems.