This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book highlights a detailed description of the study area of this thesis: the Johor River which located in Johor River Basin, Malaysia. It also describes the data available and used in this study. The book describes the application of different cross-section spacing in 1-D hydraulic flood modelling for the purpose of understanding how its influence to the model output does. It demonstrates the applicability of the 2-D hydraulic flood modelling to simulate flood inundation output using the different resolution of DEMs which built from different techniques of re-sampling. The book addresses the research question number two by using different sources of DEMs and remote sensing data in 1-D hydraulic modelling. It also addresses the third research question by comparing deterministic and probabilistic approaches for floodplain mapping using 1-D hydraulic modelling.