This paper considers different approaches through which various types of data, originating from different sources, can be integrated and used to improve the reliability of levee assessment. The objective of this paper is to show levee managers and engineers that the quality of the assessment can improve by enlarging the traditional assessment framework. First, a brief overview is presented of the different assessment types and purposes, and the fundamentally different types and sources of data that exist. The links between data and different failure modes for levees are explained followed by a description of the techniques that might be used to combine the different data types leading to a more accurate assessment of flood defence performance. The presented data combination techniques range from expert judgment to artificial intelligence and are explained using examples in a second paper.