Beavers reshape Mountain House creek
by Denise Ellen Rizzo
Feb 07, 2014 | 2030 views | 0 0 comments | 11 11 recommendations | email to a friend | print
Busy beavers
Mountain House Development Manager Morgan Groover points out a significant water level change in a storm basin off Central Parkway on Jan. 29, caused by the first of three beaver dams in Mountain House Creek. The dams are changing the flow of the creek, which naturally runs northeast from Great Valley Parkway to Old River.  Denise Ellen Rizzo/Tracy Press
view slideshow (7 images)
MOUNTAIN HOUSE — Gnawed tree limbs and tree stumps surrounded by a blanket of woodchips are just a few of the signs that Mountain House Creek has a few new residents — beavers.

Their dam building is reconfiguring the creek’s storm drain ponds, according to Mountain House Development Manager Morgan Groover.

“They’re making the situation not function the way we designed it,” he said.

He said the creek ponds are made up of two types of water basins, dry and wet. But the beavers’ dams are rerouting the creek and transforming all of the basins into wet basins. Groover said that configuration could be a problem in the rainy season.

“It’s not costing us anything right now,” he said. “We get the most rain in the spring, and we’d like to have it resolved by then.”

If storm drains and basins are not working properly when rain starts to fall, the community could be fined for violating the state’s storm drain laws, he said.

Mountain House Creek flows northeast from Great Valley Parkway to Old River and serves as both a flood control and a storm water management system for the community.

“It’s kind of hard for the state to fine us for something that’s natural, but we have to be concerned for the cleansing of the storm drains before it gets to Old River,” he said.

During a tour of three dams in the creek Jan. 29, Groover said there are probably two beavers for each dam, a male and a female.

He said the first dam appeared four or five years ago in the creek adjacent to Central Parkway. He speculated that the other dams might have been built by the original pair’s offspring but said that hadn’t been verified.

At first glance, it’s hard to tell the animals are living in the waterway, but their handiwork is evident throughout the area.

Cut trees along the creek bed initially appear to have been trimmed by landscapers from Mountain House Community Services District. But inspection of tooth marks in the stumps makes it apparent that beavers were the lumberjacks.

Groover said the next sign of their presence in the area is a dramatic difference in creek water levels near the bridge. The water under the bridge is visibly 2 to 3 feet lower than the adjacent pond.

“They’re altering the design of our storm drain cleansing pond,” he said.

Beavers’ dens, called lodges, constructed out of sticks, twigs, rocks and mud, are generally within 50 feet of their dams, but Groover said the animals remain hidden from humans. Beavers build dams to keep water levels high around their dens.

One of the newer dams in the creek is near a footbridge a few hundred yards from the front door of Bethany School, 570 S. Escuela Drive.

That dam is easily spotted along the creek bed, with protruding tree limbs and fortification. Nearby, several trees show various degrees of beaver activity, from sharp tips where limbs once grew to gnawed layers of external bark.

The dam has become a popular site for residents to watch the beavers in action, usually when human activity in the area is quiet, Groover said. Beavers are most active at night.

The question the town’s leaders must answer is what to do about the animals, which are damaging plants and threatening the storm water system.

Groover said he had been talking with people at the California Department of Fish and Wildlife about solutions.

One option is to persistently break up the dams to frustrate the beavers and urge them to move downstream toward Old River. Another option is to kill them in traps.

“We don’t want to kill them,” Groover said. “We’ll try to do the least invasive, so we’re trying to figure out what that is.”

• Contact Denise Ellen Rizzo at 830-4225 or

Comments-icon Post a Comment
No Comments Yet

We encourage readers to share online comments in this forum, but please keep them respectful and constructive. This is not a space for personal attacks, libelous statements, profanity or racist slurs. Comments that stray from the topic of the story or are found to contain abusive language are subject to removal at the Press’ discretion, and the writer responsible will be subject to being blocked from making further comments and have their past comments deleted. Readers may report inappropriate comments by e-mailing the editor at