During Indochina’s southwest monsoon, which occurs annually from May through October, the Mekong River becomes engorged with rainwater. Because the great river cannot absorb the vast amounts of runoff streaming off the jungle-covered highlands of Laos, the plateaus of the Annamese Cordillera, and the agricultural lands of east-central Cambodia, the stream is pushed up and over its banks. Once unleashed from the confines of it channel area, the Mekong spreads its tan waters over thousands of square miles of Cambodia and Vietnam.
In flood, the Mekong’s waters overwhelm the land’s linear, clearly defined features. Squared rice paddies, straight roads, and angled canals disappear beneath an ocean of water. At the height of the monsoon season in September and October, when the river attains its greatest areal extent, untold numbers of Cambodians and Vietnamese living along the lower Mekong are forced to abandon their geographical hold on the land. They take to houseboats, river galleys, and sampans. Foot and motorized traffic comes to an end. Fishing substitutes for rice cultivation. And month after month is spent living atop the waves.
One of the regions noticeably affected by the Mekong’s annual flood lay due west of Saigon. French colonists referred to the area as the Plaine des Joncs. In the 1950s and 1960s, American military personnel knew the place as the Plain of Reeds. The plain is not a plain in the traditional sense, it possessed neither herds of wild ungulates or expanses of dry-land grasses. Rather, it would be more appropriate to consider the plain a large seasonal wetland.
Prior to its agricultural development in the years after the end of the Second Indochina War in 1975, the plain was an extensive depression in the shape of a rough rectangular. When the Mekong coursed over its banks, it poured its water down into the plain, covering the plain with between one and six feet of water. Its size fluctuated from year to year, depending on the volume of water entering it. The French included portions of Cambodia and Vietnam within its boundaries. At one time it encompassed 5,903 square miles, with the largest section (4,038 square miles) within South Vietnam. Its borders ran from just south of the Cambodian river town of Banam east to South Vietnam’s Vam Co Dong River. From there the marshland extended southward to the delta community of Tan An. It then angled westward in a nearly straight line to the town of Cao Lanh. From Cao Lanh, the border of the Plain of Reed’s traced the Mekong’s left bank back to its starting point near Banam.
The Plain of Reeds acted as a floodway for the Mekong River. When the plain filled with water, it lowered the river’s flood crest, ensuring that other region’s of the delta remained high and dry from the floodwaters. Essentially, the plain acted as a natural reservoir, skimming away some of the river’s high flows and then gradually releasing the floodwater back into the main stem as the crest passed on downstream.
Because of the plain’s low elevation in relation to the Mekong, and its frequent inundation, it did not possess as many settlers as the more arable, less flood-prone regions of the delta. In the 1960s, the Plain of Reeds, like the Rung Sat, the U Minh forest, and the southernmost tip of the Ca Mau Peninsula, was one of the least populated regions in the delta. The delta as a whole averaged 150 people per square kilometer (.62 square miles). But the plain only possessed a population density of 25 people per square kilometer. A combination of factors kept settlers out of the Plain of Reeds. Besides the annual inundation of the area, the soil within the plain contained high levels of sulfates, which impeded rice cultivation. Additionally, the plain’s low-lying wet soils hindered the construction of stable roadways, which in-turn limited the area’s access to outside markets. The author of a 1969 study on the plain noted that even at that late date the region’s dirt roads were of “marginal use.” There were canals through the Plain of Reeds, but the number of navigable waterways through the plain paled in comparison to other region’s of the delta possessing better drainage.
Settlements within the Plain of Reeds consisted of rows of thatched-roofed huts placed along both sides of the area’s canals. When French engineers, with Vietnamese corvee labor, dug the waterways, they dumped the dredge material along the immediate edges of the canals. As a result, the bank lines stood higher than the surrounding marshes. It’s here, on top of the only high land within the plain, that settlers erected their elongated villages. The same settlement pattern existed along the area’s rivers. Since the immediate banks of the Mekong, Vam Co Tay, and Vam Co Dong stood above the marshes, settlers put their huts on those banks.
The region’s vegetative mosaic consisted of clumps of trees, native grasses, and reeds (which grew as high as twelve feet). At the peak of the Mekong flood, the reeds reached above the water line. On sunny, windy days, the reeds waved back and forth – a mat of green swaying over the sparkling water below. Because of its inaccessibility and low population density, the plain possessed more biological diversity than the heavily populated regions of the delta to the south and southeast. At least 127 different species of plants grew in the plain, including Cassia grandis (a tree species), Nymphacea nouchali (a species of lotus), and wild rice oryza rufipogon.
The swampy remoteness of the plain made it a haven for insurgents. When the French first seized Cochinchina in the 1860s, Vietnamese rebels fled to the plain to escape imprisonment or death at the hands of the French colonists. A century later, the Viet Cong and soldiers of the PAVN (People’s Army of Vietnam) utilized the plain as a base area. They infiltrated men and materials into South Vietnam from Cambodia through the plain. They also cached weapons and supplies in its widely-dispersed villages. Communist forces also used the plain as a jumping-off point for attacks on the U.S. 9th Infantry Division base at Dong Tam and the South Vietnamese provincial government headquarters at My Tho.
To the Americans, the plain was a marshy region with open expanses of water, blinding sunlight, piss-warm stagnate water, and unfriendly Vietnamese. In 1968, a member of the 9th Infantry Division wrote the following about the plain, “…veterans here say that the Plain of Reeds is very similar in climate and terrain to the Everglades in Florida, but there aren’t any alligators to worry about – just leeches, snakes, millions of malaria infested mosquitoes, and of course, the Cong!”
To the communists, the plain was a refuge from American bombs and heliborne troops. The Americans may have owned the plain during the daylight hours. But at night, the Viet Cong laid claim to it. The Americans hated the place – for its heat, its bogs, and its lack of a firm, dry footing. GIs and ARVN troopers came to it in helicopters, gunboats, and mean-looking hovercraft, but they never remained for long. It was too difficult to stay. But the Viet Cong never left.