The roar of the plunging cascade and the fine spray that rises 500 m above Victoria Falls are aptly captured in the great cataract's local tribal name, mosioatunya--the smoke that thunders. Above the falls, the Zambezi River, which divides Zimbabwe and Zambia, is nearly 2 km wide, and its foaming 100-m descent into white-water gorges below makes Victoria one of the natural wonders of the world and the biggest scenic attraction in sub-Saharan Africa.

That popularity carries a price in the form of empty beer cans and plastic bags that bob among the reeds of the Zambezi riverbanks; sewage pollution from backpacker camps and an overcrowded and unhygienic native township; the disturbance of wildlife by mushrooming hotel developments and jetties along the Zambezi shore; and the regular clatter of helicopters and airplanes in "Ride the Rainbow" flights over the waterfall. The wondrous falls are themselves falling victim to a common environmenta l hazard: tourism overload.

Ironically, the environmental threat is a result of another blessing: civil peace. Since stability came to Zimbabwe in 1980, after years of guerrilla warfare, tourism has increased rapidly. In the past 10 years, it has quadrupled to a current level of some 290,000 visitors a year. Unless checked, it is expected to rise to 1.5 million in the next decade. Hotel and lodge construction at the falls is booming: there are now 10 major hotels on the more popular Zimbabwe side, two are under construction, and two more are planned. By 1997 there will be some 1,850 rooms available for visitors, up 400 from this year.

Local residents are concerned that the sewage-treatment plant in the little town of Victoria Falls cannot cope with the expansion and that the pollution from the added refuse ends up in the river. Some of the hotels have been built directly on natural game corridors. As a result, elephant and buffalo are painfully diverted from their customary paths by electrified fences. On a dark night this month, a driver ran into an elephant along the main road between the hotels. The animal was unhurt, but the car was a write-off.

A new World Conservation Union report warns that unless a master binational plan to regulate the tourist industry is put into force, facilities at Victoria Falls will be strained "beyond acceptable limits." The W.C.U. report also cautions tha t the falls already has as many aircraft flying overhead as it can stand and that the noise from the flights contributes to the loss of the "natural wilderness value" of the area. There have been no in-flight disasters yet, but local residents a re up in arms about the traffic overhead. "It's like bloody Vietnam here," shouts Scottish-born Sandy Innes, waving his fist at a swirling helicopter. "They used to fly right over my place until I threatened to shoot the buggers down."

Innes, 69, a crusty former railwayman, fights an unrelenting battle against commercial encroachment from his retirement house a few hundred meters from the soaking spray of the falls. He regularly fires off letters of complaint to Zimbabwe government d epartments, newspapers and conservation organizations. Among his charges is the accusation that an uncontrolled increase in cruises and canoeing on the Zambezi is a major disturbance to wildlife and vegetation on the river and its banks. Occasionally, the wildlife fights back. Earlier this year a canoe ventured too close to a Zambezi hippopotamus and her calf. The animal charged the canoe; one guide drowned, and another lost an arm.

"Sometimes there are as many as 70 canoes operating on the river just above the falls," says Innes. "A bunch of canoeists splashing water at each other inhibits the free movement of the river wildlife. No wonder the hippos get upset.&quo t;

White-water rafting on the Zambezi below the falls also presents environmental problems, says Innes, not from the rafting itself but from a rash of riverbank camp- sites and damage to the virgin bush caused by the supply and recovery vehicles of the ra fting companies. "There's just no control," he says. "Everyone just seems to be able to do whatever he likes."

In his fight for the falls, Innes has found an unlikely partner in a black hotel worker, Stanley Katsenga, 19, who has almost singlehandedly revived environmental issues in Victoria Falls. As chairman of the Elephant Hills Conservation Club, Katsenga h as launched environmental-awareness campaigns and has traveled to Harare, the Zimbabwe capital, to plead with politicians for help to save the falls. One of his crusades is for government and private aid to clean up Victoria Falls' teeming black township, Chinotimba. It is an overcrowded "environmental time bomb" of dirt and disease, he says, in which aids is rampant and cholera could erupt at any time. Katsenga says he was a Boy Scout and learned always to leave a campsite exactly as he found i t. "That's how we need to approach tourism in Victoria Falls. If it isn't well managed, it will kill itself."

Yemi Katerere, the W.C.U.'s southern African director, agrees. "A master plan for the management of Victoria Falls has to be drawn up as a matter of urgency," he says. Such a policy, says Katerere, would regulate tourism down to the number of people allowed to trample through the rain forest. It would even control the curio wood-carving industry, which is blossoming with the increase in visitors and raising the threat of deforestation and loss of biodiversity in areas close to the falls.

The W.C.U. has called for a halt to any further expansion plans for the falls area until such a master strategy is in force--a suggestion that the Zimbabwe government has already dismissed as "imprudent." There are signs, however, that the Za mbian and Zimbabwean authorities may be prepared to discuss the setting up of a joint commission to manage the falls area. But that could take as long as two years, environmentalists say. During that time, more tourists will be splashing up and down the Z ambezi, trampling the rain forests and bungee jumping from the middle of the historic bridge over the Zambezi below the falls--a craze that attracts 7,500 daredevils a year. And until something is done, the landscape assaulted by the reckless visitors wil l be more tattered every day.