In the Gansu province of north-west China, the Po River separates the humble village of Maosi into two parts. This has a significant effect on its inhabitants, especially during floods. Crossing the river is an essential ritual of daily life, forming the route for many, including that for children between home and school. When the water rises above ankle depth, the only means of crossing it has been to build a primitive bridge from mud, straw and tree branches--exploiting the limited ...