**Jeroen C. J. H. Aerts**

Institute for Environmental Studies (IVM), VU University Amsterdam, De Boelelaan 1087, 1081HV Amsterdam, The Netherlands; jeroen.aerts@vu.nl

Received: 29 September 2018; Accepted: 8 November 2018; Published: 13 November 2018

**Abstract:** Floods are the most devastating of global natural disasters, and flood adaptation measures are needed to reduce future risk. Researchers have started to evaluate the costs and benefits of flood adaptation, but information regarding the cost of different flood adaptation measures is often not available or is hidden in non-peer-reviewed literature. Recent review studies have explored cost estimates for different aspects of flood adaptation, such as nature-based solutions. This study aims to contribute empirical data regarding the cost of flood adaptation by compiling peer-reviewed literature and research reports. The focus is on construction costs and expenses for operation and maintenance. This paper integrates the unit cost information of six main flood adaptation measure categories: (1) the flood-proofing of buildings, (2) flood protection, (3) beach nourishment and dunes, (4) nature-based solutions for coastal ecosystems, (5) channel managemen<sup>t</sup> and nature-based solutions for riverine systems, and (6) urban drainage. Cost estimates are corrected for inflation and converted to U.S. dollars (2016). Measures are described, and cost figures for both developed and developing countries are provided. The results of this study can be used as input for economic-assessment studies on flood adaptation measures.

**Keywords:** flood; cost; adaptation; flood management; cost–benefit
