A state of the art review on High Water Mark (HWM) determination

The High Water Mark (HWM) is an important cadastral boundary that separates land and water. It is also used as a baseline to facilitate coastal hazard management from which land and infrastructure development is offset to ensure the protection of property from storm surge and sea level rise. The determination of the HWM has a long history. Its definition, the mean and even the corresponding determination methods have changed through time. In addition, the location of the HWM is difficult to define accurately due to the ambulatory nature of water and coastal morphology variations. ter understand the HWM determination, this paper reviews the development of the definition of HWM, including ordinary high water mark (OHWM), mean high water mark (MHWM), mean high water spring (MHWS) and mean higher high water (MHHW), and the existing HWM indicators, such as vegetation line and beach morphological features. Two common methods of HWM determination, field survey and remote sensing, are discussed in this paper. This is followed by the investigation of the possible factors that influence the variation of the HWM position. Furthermore, an overview of the ambulatory nature of both water and coastal morphology, which contributes to the difficulties in HWM determination, is provided. Finally, the limitations of previous determination methods and future direction in HWM determination studies are also discussed. This study concludes that it is necessary to develop a robust analytical system to identify, evaluate and integrate various factors into the process of determining the HWM.