Situation on river dikes A network of river dikes of a total length of more than 5000 km covers the delta of the Red River in Vietnam. The social and economic development of the region around the capital Hanoi largely depends on the safety of the dike system. Monsoon rains cause a rise of the water level of most rivers in this region up to 13 m above regular level. Every year during the rainy season, the water flow results in a strong pressure on the dikes and their fundaments. Despite of thousands of people who are engaged every year to strengthen and to repair the dikes, damages caused by seepage, slides or fractures are not exceptional. The dike network has been constructed, maintained and extended for many centuries using the locally available material. Since some dike sections are crossing old lakes, ponds or even abandoned waste dumps stability problems are unavoidable. Other sections suffer from foundation damage caused by piping. A specific problem of Vietnamese dikes is the damage caused by different species of termite population. The geophysical work on dikes aims at a better recognition of severely affected sections. A joint project between Vietnamese and German geophysicists (Weller et al., 1996) was launched to test a combination of different geophysical methods to investigate two dike sections. The technology to survey dikes in Germany is based on geoelectrical methods and penetration soundings.