Geotextile encapsulated sand elements are three-dimensional systems manufactured from textile materials, non-woven materials or combinations of textile and non-woven materials that are filled with sand on-site. These systems are relatively new and the number of applications is growing in river and coastal engineering. Quite often Geosystems are mentioned as a possible solution, but planners, designers and contractors feel rather hesitant about the application of geotextile encapsulated sand elements due to a lack of experience and adequate design rules. The use of geosystems has the advantage that local material can be applied and that no (expensive) quarry stone needs to be extracted and transported from the mountains to the site. Compared to traditional construction methods (with quarry stone) the application of geotextile sand filled elements may add considerable operational advantages to the execution of marine works and may offer attractive financial opportunities. In the application of geotextile encapsulated sand elements however, proper attention should be paid to the laying down of different responsibilities of the parties in the contract. In Geosystems. Design Rules and Applications four types of geotextile sand elements are distinguished, each with specific properties: geo-bags, geo-mattresses, geotextile tubes and geotextile containers. The focus is on the use of geosystems filled with sand as a construction in river and coastal engineering. Geosystems filled with sludge are not covered. The chapters “Introduction” and “General design aspects” are followed by four chapters of the same structure dealing with the various systems. Each of these four chapters starts with a general description and applications and ends with a calculation example. Design aspects are dealt with in the remaining paragraphs. Geosystems. Design Rules and Applications is based on research commissioned by the Dutch Rijkswaterstaat and Delft Cluster. The realisation of the Dutch version was coordinated by a CUR-committee. The English version is a translation of the Dutch version (CUR-publication 217). However, new developments have been added and the text was checked once again and improved. Geosystems. Design Rules and Applications is an essential reference for professionals and academics interested in River and Coastal Engineering, but aims also at those interested in Geotechnical Engineering.