The presence of water has a major influence on the design of soil structures as it reduces the effective stresses and hence shear resistance, and applies seepage forces in case of flow. This key topic is well known to every geotechnical engineer and the design principle for soil structure is to drain groundwater, infiltrated surface water or seepage water in a controlled manner from the soil. However, for soil structures whose purpose is to retain water, such as embankment dams impounding a reservoir, or dikes for flood protection along rivers and channels, both sealing and draining have to be ensured by the structures. With simple construction measures such as filter and drainage zones incorporated in earth structures composed of selected and treated materials, the stability and safety of these structures can be improved considerably. This paper discusses seepage control measures as well as the selection and design of appropriate filter materials.