National Geographic : 1987 Jul
N AREA no larger than Wisconsin, Bangladesh has struggled since in dependence in 1971 to feed its people, now numbering 107 million. It is one of the world's most densely populated na tions. For years the country as flat and riverine as the Netherlands-has constructed earthen levees across tidal creeks to protect flood-prone cropland. Usually the dams are built out from each bank by filling compartments with palm leaves, brush, and clay. The narrowed gap, where the tide rushes at ever increasing velocity, must be sealed within one intertidal period. But sometimes the force of the tide scours out the bottom, destroy ing the partial dike. For the closure of the Feni in 1985, I, as consulting engi neer with the Dutch firm of Haskoning, drew on a decade of experience in adapting old time Dutch methods to the Bangladesh circumstance. Construction began with the sinking of huge mattresses (diagram, 1) to protect the river bottom from erosion. Boulders and clay bags were dumped in gullies to make a level sill (2). Over this base more bags were stockpiled (3) until closure day. Then teams hoisted bags into the gaps (red arrow), creating the barricade (4). Next earthmovers raised the dam's height (5) with clay. The structure was faced with concrete and bricks (6). A supervisor for the general contractor, Japan's Shimizu Construction Co. Ltd., led warm-up exercises (below) to instill a sense of teamwork. Many workers like this Ben gali (left) protected their heads with sacks against the drip ping bags of clay; they earned five takas (20 U. S. cents) for each bag carried. Some men proudly lifted two at a time. The February28, 1985, closure was timed to coincide with the lowest tides of the dry season.