A review of approaches for water depth estimation with multispectral data

The purpose of this paper is to give an exhaustive assessment of water depth estimation in shallow inland and coastal water environments with the assistance of optical remote detecting procedures, utilizing satellite/airborne multispectral information. Remote sensing has been used to map bathymetry for several decades. Inaccessibility, large‐scale depth mapping, very shallow areas, and cost constraint are some of the reasons why remote sensing technique is a boon for bathymetry. Researchers have come a long way since the remote sensing‐based bathymetry has been used. Fourfold increase in spatial, spectral, radiometric and temporal resolution of sensors have also increased the accuracy. There are two types of remote sensing techniques; Active and Passive. Active remote sensing includes the use of ground penetrating radar and bathymetric lidar, which are expensive but precise surveys successful up to 70 m depth. On the other hand, passive remote sensing deals with water photogrammetry and radiometric methods done by capturing imagery with space borne/air borne platforms having depth penetration up to 25 m. The latter technique includes finding of a logarithmic relationship between river depth and image values. This technique is most widely used because of its cost effectiveness. In this paper, the emphasis has been given to derive bathymetric techniques using multispectral data as these methods have proved reasonably successful when water quality, bottom reflectance, and atmospheric effects are all invariant. At a specific area, the detection of possible changes in water flow and levels indicates flow path changes which can be used to predict potential surface level flooding for better water management and policy decisions.