"They actually stop the traffic on the highway and let themselves into the river. They go up into the river and make their own trails up into the mountain and that's where they do their action," Kahaluu Neighborhood board member Lucy Salas said.
She said sometimes caravans leave Kamehameha highway to do their dirty work.
"We even requested to put up guard rails so that it would prevent this type of situation," she said.
Salas said the vehicles slice up the stream and tear away the river bank, uprooting small trees and brush that gets carried downstream during heavy rains.
Waikane resident Richard Davis agrees "mud boggers" do some damage but he said the bigger blame rests with the state.
"I don't think they cleaned this river in years," he said. "You cannot stop the water from coming with the amount of water that's coming down. But you can help it by at least cleaning the river and maybe dredging it if possible."
Davis owns Island Fruits, a roadside stand next to Waikane bridge. He's frustrated by how often it floods.
"I understand their frustrations and they have a right to be frustrated because this is their neighborhood. They see damage every time it floods," state Dept. of Transportation spokesperson Tammy Mori said.
State DOT road crews clear streams and bridges before heavy rains. But there are only eight workers on staff with scores of bridges to care for on Oahu.
Waikane bridge is low-lying so backed up debris can quickly turn into a dam.
"This Waikane stream bridge is set for replacement in 2013," Mori said.
The new bridge will be wider so the state hopes it won't clog as easily.