Science / Medicine : THE MAN AND THE River : Environment: Engineer Hsieh Wen Shen has a solution to undoing ecological disaster wrought in the Everglades when a concrete canal replaced the Kissimmee River a decade ago: Put back the river.

TIMES SCIENCE WRITER

If you squint just a little, it's not difficult to believe that you are in south-central Florida. To the right, stretching off into the distance, lies a ruler-straight concrete drainage canal. Water runs smooth and fast through it, unimpeded by soil, trees, bends or the other geological vagaries that give a river character and vitality.

To the left lie the graceful loops and oxbows of the old riverbed, now filled with near-stagnant water, barely moving in the dim twilight. The only thing missing is stultifying humidity and bombardier mosquitoes.

But it is not twilight, and this isn't Florida. Rather, it is a hangar-like building at the University of California's field station where UC Berkeley mechanical engineer Hsieh Wen Shen has constructed a one-sixtieth-scale model of a section of Florida's Kissimmee River and the C-38 canal that replaced it a decade ago.

On this July day, about 20 members of the South Florida Water Management District are in the Bay Area to view Shen's model and to hear what he has learned about their ambitious and unprecedented project, frequently called the largest ecological restoration project ever attempted in the United States.

Their goal is the restoration of the Kissimmee's flow from the C-38 canal back into the natural riverbed. In the process, they hope to reverse the damage that has been done to the system, including the loss of large numbers of fish and wild animals, increased pollution of Lake Okeechobee--the ecological centerpiece of the state--and diminished aesthetic values.

Shen's model is designed to tell Florida officials how to go about restoring the river most effectively--whether engineers should build sheet-metal weirs or dams, fill in the canal with dirt or use a combination of the two techniques.

If the project is successful, "it could be instrumental in stimulating other restoration activities around the country," said ecologist James A. Karr of Virginia Polytechnic Institute in Blacksburg, Va. There are a number of wetlands areas in need of such restoration, including the Chesapeake Bay in the East and the San Francisco Bay, where development has destroyed wetlands and pollution has dramatically lowered water quality.

Once, the Kissimmee was a shallow, meandering, 98-mile-long river that carried water south from Lake Kissimmee to Lake Okeechobee, from which it eventually drained into the Everglades.

But destructive hurricanes in the 1940s and 1950s whetted the public's appetite for flood control, and in 1961, the Army Corps of Engineers--at the request of Florida officials--began excavating a 300-foot-wide, 30-foot-deep concrete channel that shortened the water's path to a mere 52 miles. For the first time, boat traffic could pass between the two lakes throughout the year, and the $33-million waterway became a popular site for boating and fishing.

But the ecological impact of the channelization project proved devastating, according to biologist Louis Toth of the Water Management District. About 40,000 acres of wetlands in the flood plain, 80% of the total along the Kissimmee River, were drained and converted to pasture land. Those wetlands were home to, among other creatures, 5 billion small forest fish and 6 billion shrimp, all of which were lost, Toth said.

The area was also home to eight endangered species, including Florida panthers, cougars, ibises, as well as a mosaic of eight major plant communities. By decreasing the area where the animals and birds could grow and thrive, the canal construction greatly reduced their chances for survival.

But the one- to two-mile-wide flood plain was not the only area affected by the channelization. The wetlands filtered out man-made fertilizers and other organic materials from the river, preventing them from reaching Lake Okeechobee, which Theresa Woody of the Sierra Club calls "the liquid heart of South Florida."

But today the water speeds through the C-38 canal 11 times faster than nature intended. Pollutants are not filtered from the water but added to it, as manure is washed into the canal from adjacent cow pastures. As a consequence, the influx of rich organics into Lake Okeechobee is three times as high as it was before the canal was constructed.

The lake is so polluted now that algae blooms, as much as 100 miles wide, threaten to choke off all other life. "The way we look at it," Woody said, "is that the lake's problems have been exacerbated to the point there is a deathwatch on it."

In turn, conditions in Lake Okeechobee, combined with encroaching farmlands and heightened development in southern Florida, are threatening the entire fragile Everglades system, home to more than 30 endangered species. "Of all the national parks, (the Everglades) is the one closest to extinction," said George T. Frampton, president of the Wilderness Society.

The potential damage has been recognized for a long time. Even as the Corps of Engineers was finishing up the C-38 project in 1971, then-Gov. Reubin Askew was convening a conference to consider how to reverse the damage that had been done by the canal. That conference concluded that the "Kissimmee lakes and marshes should be restored to their historic conditions and levels to the greatest extent possible to improve the quality of the water entering Lake Okeechobee."

Nothing happened for 12 years, however, until then-Gov. Bob Graham created a coordinating council of several state agencies to oversee the restoration and preservation of ecosystems throughout southern Florida as part of the "Save Our Everglades" campaign.

By 1985, engineers had constructed three steel barriers, called weirs, along a 12-mile section of the canal to force part of the water flow back into the old riverbed.

But the demonstration project raised many questions about how to re-establish the river's flow. Should weirs be used along the entire length of the C-38 canal, or should the canal simply be filled in with dirt to plug it, forcing the water back into the riverbed? If weirs and other types of dams were to be used, what is the best design?

If the canal were to be filled in, what would be done about sections of the river that were completely obliterated during its construction? How can flooding outside the flood plain be prevented?

Enter Shen, an internationally recognized expert on river dynamics who has, among other things, headed the United Nations' study of the environmental effects that would occur as a result of construction of the Aswan Dam on the Nile River.

Beginning in 1986, Shen and his students selected a one-square-mile section of the river that was already undergoing renovation and made painstaking measurements of river and canal dimensions, water flow at selected sites, vegetation and other characteristics.

Using this data combined with extensive aerial photography, they constructed a 100-by-60-foot model of the river section. Their model, in the Richmond laboratory, incorporates plastic mesh and other fibrous materials that simulate the roughness of the brush, trees and soils.

Simultaneously, Shen's group has been developing a sophisticated computer model that reproduces mathematically what they observe physically in both the real river and the model. Ultimately, the computer model will be expanded to cover large sections of the river more efficiently than the physical model can.

With the model Shen can simulate changes in river level and flow under a variety of conditions ranging from drought to hurricanes and in any configuration: in its current state, with weirs in place, plugged with earth, or in any intermediate combination.

Neither the physical nor the numerical modeling of the river is a new technique, noted hydrologist Heinz Stefan of the University of Minnesota, but the complexity and size of this project is. "This is not a routine kind of work," he said. "There is a great deal of added complexity because of the simulation of flood plains that are heavily vegetated."

Earlier this month, Shen presented his final report and recommendations to the water district and Florida Gov. Bob Martinez. His primary conclusion: Most of the C-38 waterway should be backfilled and new oxbows should be dug in areas of the river where others were filled in during construction of the canal. Under this plan, the water would be naturally forced back into the riverbed.

Any lesser measures, he said, would create two main problems: too high a flow rate and flooding during peak rain periods.

For example, the use of weirs instead of backfilling would create myriad problems, according to Shen. If weirs are used to force water back into the oxbows, the rate of flow will be two to three times as high as it was when the river was in its pristine condition, Shen found. Such a high flow rate will be disastrous to normal river life, dislodging fish eggs from their precarious perches, sweeping away food that would normally settle to the river bottom and churning up mud and debris.

Perhaps even more important, the high flow rate created by the use of weirs would not allow the wetlands of the flood plain to be inundated as long as necessary. Those wetlands must be under water for as long as nine months of the year for waterfowl and other species to thrive. In many ways, if weirs are used, the restored river would simply be a longer canal without significant environmental benefits, Shen said.

Under storm conditions, the problem caused by weirs would be worse. Flow rates through the oxbows would be much higher, causing erosion and depositing of soil that would disrupt navigability of the river and require dredging.

The complete backfill plan, however, would mitigate all of these problems. Flow rates would be normal through more than half of the oxbows, the flood plain would be inundated for the required periods and water flow during storms would not be high enough to cause significant erosion and depositing problems.

Implementing the backfill plan, however, would require constructing 60 miles of levees along the edges of the flood plain to control the flooding that was the original reason for construction of the C-38 canal. Ironically, some argue that the whole problem could have been avoided had the state simply put in levees in the first place.

The principal objection to the backfill plan, Shen noted, is cost. Although precise estimates have not been prepared, crude estimates indicate the cost would be about $250 million. The use of weirs would be substantially cheaper.

The governor and water district are not expected to make any decisions on the plans until firmer cost estimates have been prepared, and engineering studies are expected to begin soon.

Environmental groups have pushed for the backfill plan all along because of its aesthetic values, Woody said, and they are "delighted" with Shen's recommendation. As she concluded, "We don't want to leave a legacy to our children of sheet-metal weirs in a concrete river."

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