WAIKANE (HAWAIINEWSNOW) - It's called "mud bogging."
The off-road action on You Tube shows four-wheel drives ripping into Waikane stream, rolling over the valley, and crushing whatever stands in their way.
"It breaks up the natural look of our river stream into a wider bed," Kahaluu Neighborhood Board member Lucy Salas said.
Mud bogging cuts the riverbank. Some Waikane residents think it contributes to flooding.
But there's another fear. Areas of Waikane are military property.
"There's no question that there are all sorts of unexploded military rockets, mortar rounds," Earthjustice's David Henkin said.
"It is very dangerous, especially for the ones going up into the mountains and you have different ridges along the mountain," Salas said.
Waikane residents fed up with the boggers say they congregate in caravans, especially after a heavy rain.
"Their jeeps are all mud bogged out," Salas said. "Their faces, they smell like the stink mud."
But are boggers breaking the law?
"I can't imagine that it is legal for folks to go into the stream and destroy the environment in that way without any permission," Henkin said.
Honolulu police tell Hawaii News Now they've issued some citations for tracking mud onto Kamehameha highway. They're checking on trespassing rules.