Rio Salado Update December 1997

The following also is provided in Spanish. Lo siguiente también es provisto en Español .

Come to the public meeting on Rio Salado Habitat Restoration!
What is in the plan?
As a visitor, what would you see when coming to the Rio Salado?
Rio Salado and flood control

Back

Come to the public meeting on Rio Salado Habitat Restoration!

Soon you will be able to attend a presentation of the draft Rio Salado plan, for which the Corps of Engineers just released its draft Feasibility Plan. The Army Corps of Engineers is inviting the public to a presentation of the plan on Jan. 8, 1998, at 6 p.m. at Phoenix City Council Chambers, 200 W. Jefferson Street. From 6 to 7 p.m. you can view videos and displays describing the creation of the plan. At 7 p.m., the Corps will host a public presentation of the plan and invite all attending to make or leave comments. Everybody interested in the restoration of the Salt River is invited to join the presentation.

Return to top of Rio Salado Update

What is in the plan?

In many respects it will look very familiar to those who have been following this study to date. The Feasibility Plan describes the basic approach to restoring habitat in the Salt River, an approach chosen through research and analysis conducted during the feasibility planning over the last two years. The Phoenix project will consist of about 550 acres and extend from the I-10 freeway bridge (next to Sky Harbor Airport) downstream to 19th Avenue. The Rio Salado project will create within the channel of the river a desert river habitat consisting of a small stream, wetlands and small ponds, stands of cottonwood and willow trees, mesquite groves, and desert grasslands and shrubs. In the project area, the river is between 600 and 1200 feet wide. (Click here for a map that shows the main features of the plan.)

Return to top of Rio Salado Update

As a visitor, what would you see when coming to the Rio Salado?

Driving toward one of the three public entries on 16th Street, Central Avenue or Seventh Avenue, you will first notice a line of cottonwood trees on the top of the river’s bank, stretching east and west, following the curve of the river. After you enter a small parking lot, a visitor’s center will provide information about access into different portions of the project. You also will be able to view displays about the history of the Salt River, early settlers who lived along the river, and desert rivers and the plants and wildlife that flourish near them.

From the entry point you may wish to venture along the river on the bank-top trail to view the lush vegetation growing on the river’s terrace level below you. Rapidly growing cottonwood and willow trees soon will be 60 feet tall. In their shade lie wetlands and marshes hosting uncountable birds, many of which take to wing upon your approach. Further along the trail, through the trees, you will glimpse the main stream, meandering in the lowest channel through its gravel bed or occasionally into a small pond. Farther down, you will hear the sound of water, as the stream drops over a concrete structure designed to slow the flow of storm waters and then flows into a pond before it quietly continues on its way.

Near each public entry will be a trail leading down to the terrace level where much of the riparian habitat and wildlife is located. The trail will take you through some of the mesquite groves growing on higher ground near the banks, through some of the open fields of grasses and shrubs, to the beckoning cool shade offered by a massive stand of cottonwoods. Walking in the silence of the trees, you will be able to hear the sounds of birds and insects or the occasional scatter of some rabbits. Along the way you will pass some of the wetlands and small open ponds that support the rich mixture of wildlife and habitat that makes desert rivers the source of so much of desert life. Signs will explain the makeup and function of the habitat you are discovering here.

From the terrace, you also may want to venture down a few ramps into the main channel zone, which is cut deeper for storm flows. Left essentially unaltered except by the wash of storm flows, the channel is a natural walkway of cobbles and sandy areas.

A small stream, supporting more wetlands and ponds, wanders as gravity would take it through this zone. Vegetation consists mainly of low grasslands and shrubs. In the heat of the day, you may wish to explore more along the edge of the channel in the shade of the cottonwoods and willow trees growing along the banks of the nearby terrace. Continuing along the channel, you will encounter one of the project’s four "drop structures." These rustically designed concrete structures control the slope of the river bottom to make sure most storms do not damage the project’s habitat. But for now, the structures offer the delightful sound of water cascading over and down into a clear pool at the base before the stream picks up and continues wandering its way downstream.

On some days you may wish to visit the project just to enjoy a more lengthy walk or bike ride along the bank tops, where a total of 10 miles of trails will lead you along both sides of the project on a continuous route. If you are an equestrian, you also can use the horse trail to follow the same route. As the Rio Salado is the first phase of the restoration of the entire river, you eventually will be able to extend your trail experience along the river from Tempe on the east to Phoenix’s 91st Avenue Wastewater Treatment Plant on the west.

To support this environment, six wells, three located on each side of the river, will be drilled into the shallow aquifer under the river to provide the 6 million gallons of water needed daily. Water will be fed into an irrigation canal along the bank tops to wetlands and ponds. It also will be sprayed onto woodland areas with high-pressure irrigation spray heads, delivering controlled amounts to the specific vegetation areas. Test wells will be drilled to locate the best quality groundwater, but if needed, treatment will be provided at specific well sites to ensure compliance with all state and federal regulations.

The low-flow stream channel and the terrace are designed to function with the frequency and volumes of expected storm releases. In protecting habitat by controlling stormwater velocity, the length of time that plants would be flooded, and flooding frequency, the Rio Salado project is replicating, to the extent possible, natural systems that protect desert riparian areas during flood events.

Since major storm releases, occurring at average intervals of 25 years or more, are likely to impact habitat and improvements, all major infrastructure will be located out of the river channel. A "sinking" fund will provide resources needed to replace pathways and signage, remove silt buildup, and regrade where needed after very large storm flows. Much of the vegetation will survive most storm releases, while other plants will regrow from established root systems and storm-spread seeds as the result of the continuing supply of water into the project. To a large extent, the Rio Salado is breaking new ground in restoring a desert river habitat in the heart of an urban region and within a greatly altered physical setting. The city and the Corps of Engineers recognize that much experimentation and change will occur as the habitat gets established and that the project will evolve and grow as a new natural habitat balance is created. Habitat locations may change; new species even may be tested. To help ensure success of the project, a flexible, adaptive habitat management approach will be used in addition to an extended period of joint participation by the corps in the project’s early years.

The corps’ plan is expected to be approved by mid-1998 and then will go to Congress for authorization as part of the Water Resources Development Act next summer. If the entire community gets behind the WRDA and it is approved, engineering design can be completed by mid-2000, and the project can be ready to go to construction by the year’s end. That means the first phase of the Phoenix Rio Salado can be finished and open to the public by the year 2003 - just six years from now!

Return to top of Rio Salado Update

Rio Salado and flood control

Many people in the Phoenix area have never seen the Salt River flooded because big storms come to the desert rivers so infrequently. A major storm flow of about 160,000 cubic feet per second statistically occurs just once in 100 years. But when such a "hundred-year" storm does occur, it increases the river’s water flow to many times its normal level. That’s why few cities in deserts are built in river valleys or along river banks, as huge floods could wipe out an entire town.

To a large extent, the Bureau of Reclamation dams operated by the Salt River Project have done a wonderful job of reducing the Salt River’s peak flood flows. Still, when big storms fill SRP lakes, stormwater must be passed into the Salt River bed. In addition, dams on the Verde River are quite small and most major storms pass quickly through them.

As a result, the Phoenix area still faces the threat of major floods, which we have no way of predicting. As recently as the winter of 1992-93, we saw peak flood waters of almost 100,000 cubic feet per second in the Salt River and, at the west end of the Valley, the river was running a mile wide. The banks of the river in Phoenix presently can contain a "hundred-year" storm, and the Rio Salado Project must continue this flood-carrying capability. We can do this by duplicating the features and ecological processes that occur in natural rivers. A low-flow channel will duplicate the main channel found in natural streams. It will be about 10 feet deep and 200 feet wide and will carry 12,200 cubic feet per second. The side walls will be stabilized to withstand high flows, while the bottom of the channel will be shaped by the storm flows themselves. Low dams - or "grade control structures" - in the river bottom will slow velocity to reduce damage from fast-moving water. Trees will survive most floods so long as they do not stay under water for more than 30 days. The low-flow channel will be sized so it can carry storm releases that last that long.

Every few years, storm releases will overtop the low-flow channel onto the terrace level (today’s river bottom), which is where most of the trees, wildlife and other habitat will be located. Flowing relatively slowly, these storms will do little damage and actually will help replenish soil moisture and flush out soil salts. Other than trails and interpretive signage, there will be few manmade improvements in the terrace or the low-flow channel, meaning little potential for losses during typical flood events. Major features of infrastructure - wells, canals and water delivery pipes, most trails, service roads and public entry facilities - will be placed on the river banks above the flood line. Even banks of the low-flow channel will be lined so it will continue to function during and after floods.

Still, there will be major storms, like those of 1992-93, 1978-79 and 1979-80. Such storms that come once in 25, 50 or 100 years cause damage to habitat in natural streams as well as the Rio Salado. Trees will be uprooted and the channel may change. Trails, signage and other interpretive facilities on the terrace will be lost during storms and will have to be replaced. In summary, the Rio Salado can actually benefit from most storm flows, but will lose some habitat and facilities after the large, infrequent desert storms that cause large releases of water into the river. Once storm flows subside, natural habitat grows back quickly as stream flow restores favorable flowing conditions along streams and rivers. The city will manage the project to set aside money for those times restoration is needed.

Return to top of Rio Salado Update