It's park of a decision to get visitor fee money to support state parks. The other parks I know of that charge now are Nu'uanu Pali and Diamond Head on Oahu, Iao Valley on Maui. Hapuna, Makena, and Haena are on the slate.
The $1 is the non-resident walk-in fee.
Here's some info from the Parks people:
“Fees paid by our commercial and out-of-state visitors to high traffic parks, will help offset the shortfalls currently facing the state parks budget,” Dan Quinn, State Parks administrator. He said the fees will help to generate new sources of income to help the parks system gain more self-sufficiency.
In the fall of 2009, the Hawai’i Business Roundtable asked residents their opinion on measures to either increase taxes, or reduce services in order to keep state parks open. The most popular opinion, favored by 58%, was to charge entrance or parking fees, but exempt residents.
The Board of Land and Natural Resources authorized the implementation of either parking fees or entry fees, but not both at the same location. The Parks department then identified parks with a high volume of non-resident traffic, and organized informational meetings
the Division of State Parks to set either parking fees or entry fees (but not both at the same location) at specific state park locations across the state. The Parks division identified parks with high volume non-resident traffic to implement either parking or entry fees. Other parks on the list for future discussion include Hapuna on the Big Island, Ha’ena on Kaua’i, and Makena on Maui.
http://mauinow.com/2010/12/16/new-non-re...aka-falls/