There have been virtual fences, real fences, increased patrols and night-vision cameras. Now the latest initiative by the US to seal its increasingly porous border with Mexico harks back to one of the oldest approaches: dig a moat. City officials in Yuma, in south-western Arizona, have come up with a scheme to create a "security channel" along the nearby border by reviving a derelict two-mile stretch of the Colorado river.

"The moats that I've seen circled the castle and allowed you to protect yourself, and that's kind of what we're looking at here," Yuma county sheriff Ralph Ogden told Reuters. The scheme would see engineers dig out a two-mile stretch of a 180-hectare (440-acre) wetland known as Hunters Hole.

Once a haven to anglers, ducks and the Cocopah Indians, the area is now a thicket of tamarisk, forgotten shoes and old cars providing cover for smugglers and border crossers. But under the plan, all that would change. The banks of the river would be replanted with native cattail, bulrush and mesquite, and wells would supply water to the wetlands as well as to a 20-metre-wide, three-metre-deep channel that would run the length of Hunters Hole.

With the replenished river marking the frontier, would-be border crossers would have to scale a 4.5-metre levee - built with the earth excavated from the riverbed - cross a 120-metre-wide marsh and then ascend another levee on the northern side of the wetlands.

"In order to restore Hunters Hole, we're going to have to secure it," a border patrol agent, Carlos Dominguez, told the High Country News. The moat plan has won broad local backing, unlike other border security schemes which have angered environmentalists and land-owners.

In Texas, more than 100 landowners have resisted government efforts to build a fence across their land. Environmentalists also launched a lawsuit to block fence construction on the border in Naco, in eastern Arizona. However, the department of homeland security is under a strict timetable to build 670 miles of new fencing by the end of the year. With failed efforts to build a virtual or electronic barrier, attention has again focused on a physical barrier.

As well as illegal immigration, the desolation of many border areas has attracted criminal activity. The 23-mile stretch of the Colorado river that runs along the Mexican border near Yuma has seen two murders since 2004 and 250 armed robberies in the last two years. "It's in the United States, but it's become a no-man's-land, an area where bodies were dumped, where people and drugs were smuggled over the border," said Ogden.

Backers of the Yuma plan - more than 30 local groups, including the border patrol and the city's elected officials - hope that Hunters Hole will mimic the model of another local wetland that was rescued from dereliction and crime and now provides bicycle paths and fishing.

"What you are building is a moat, but it's bringing the life and the wildlife back," said Ogden. "It doesn't take much brainpower to build a 12-foot high fence around something, but this is unique."

· This article was amended on Wednesday March 26 2008. Yuma county sheriff Ralph Ogden, quoted in the article above, spoke to the Reuters news agency and not to Associated Press. This has been corrected.