It's been more than 60 years since flood control engineers converted the Arroyo Seco stream into a concrete flood channel. Now, a group of nonprofits suggests, the time has come to restore the channel to its natural state.

A new study outlines how local, state and federal agencies, in partnership with private organizations, could restore the Arroyo Seco and its tributaries.

The proposal suggests the creation of a flood plain system to handle periodic flooding, protecting native habitat and improving recreational opportunities along the corridor.

"While we all realize that we are not going to return this area to what it was before European settlement," said Arthur Golding, an architect and urban planner with the Los Angeles and San Gabriel Streams Watershed Council, "balance can be achieved."

The Arroyo Seco Watershed Restoration Feasibility Study, in the works for two years, was produced by North East Trees and the Arroyo Seco Foundation.

During a meeting at Caltech late Wednesday to introduce the plan, Tim Brick, director of the foundation, said the study was "setting the course for the future of the Arroyo Seco."

Arroyo Seco refers to the stream that, depending on the season, often trickles and occasionally roars for 22 miles from its beginning in the Angeles National Forest to the Los Angeles River. It is also used to describe the long, winding canyon carved by the stream.

According to Brick, the Tongva tribe, the first inhabitants of the area, called the area Hahamongna, or "flowing water, fruitful valley."

The Spaniards, who Brick joked must have found it in late summer, named it Arroyo Seco: dry gulch.

The watershed, the area that drains into the Arroyo Seco, encompasses 46.6 square miles--almost twice the size of Pasadena--and includes parts of the Angeles National Forest, Altadena, La Canada-Flintridge, Pasadena, South Pasadena and Los Angeles.

Many of the tributaries that once fed into the Arroyo Seco have long been buried by development and efforts to control the often unpredictable stream. The watershed includes residential neighborhoods and public parks that many environmentalists hope eventually will be connected into a greenbelt along the arroyo.

Can the Arroyo Seco be restored? That was the question Wednesday evening. The answer: a qualified yes.

"It is time," the study concludes, "to make urban stream restoration a reality, in a place many thought it impossible--the largest metropolitan region in the United States with the most extensively engineered flood control system anywhere in the world--Southern California."

The report, which was funded in part by the California Coastal Conservancy and the Mountains Recreation and Conservation Authority, lists 11 pages of recommendations including almost 80 proposed projects.

In addition to the plan to remove the concrete from the Arroyo Seco south of Devil's Gate Dam in Pasadena and replace it with a natural stream and flood plain system, some notable projects include:

* Linking trails between Millard Canyon in Altadena and Hahamongna Watershed Park in Pasadena.

* Renovating the Brookside Golf Course in Pasadena with native vegetation and a natural stream bed.

* Improving the network of trails and bikeways in the lower arroyo.

* Enhancing wildlife habitat and passive recreational uses of Ernest E. Debs Regional  Park in Los Angeles.

* Creating a system of pedestrian walkways to connect the Southwest Museum, the Lummis Home, Heritage Square and the Casa de Adobe in Los Angeles in a cultural corridor.

* Establishing a public open space in the vicinity of the confluence of the Arroyo Seco and the Los Angeles River.

This is the first study to look at the Arroyo Seco watershed as a whole, Brick said. Related plans by the U.S. Forest Service, Pasadena and Caltrans focus on parts of the watershed.

Pasadena introduced a five-volume Arroyo Seco Master Plan for the 1,000 acres of the arroyo within city boundaries in May. It has drawn criticism from citizens groups, which say the plan favors infrastructure development and recreation to the exclusion of conservation.

The city has extended the public review period for the plan's draft Master Environmental Impact Report to Sept. 16 to allow the public time to study the document.

Brick said Wednesday that it is up to members of the public to decide how the Pasadena plan and the watershed study should be integrated.

Whether the Arroyo Seco stream can be returned to its former state safely is a question that may be answered by the Army Corps of Engineers. The corps is finishing its own study of the Arroyo Seco. The next step, according to a spokeswoman, would be to study whether the watershed plan is feasible.

There are many other hoops to clear before full restoration of the watershed becomes a reality--including obtaining funding and getting a number of government agencies to sign off on the projects suggested by the study.

The two-volume Arroyo Seco Watershed Restoration Feasibility Study is available on the Arroyo Seco Foundation Web site: www.arroyoseco.org/Watershedstudy.htm