Bridge over Rio Huanuni, Bolivia

Rio Huanuni is dominated by alternating mud flows and scour events, resulting in vertical variations in the riverbed elevation of approximately 5 to 8 meters. Construction of piles for a bridge over this river was threatened by river meander and lowering of the bed elevation to 2 m below the design invert of the pile cap. The firm undertook a geomorphic assessment of the problem, which predicted even more severe problems in the future as the base level of the river dropped at its point of discharge to Rio La Paz. Local countermeasures were designed based on use of vanes constructed from piles driven into the weak alluvial material to help maintain the river between the bridge supports, plus diversion of the downstream portion of the river channel to another point on the alluvial fan.