oa Remotely sensed empirical modeling of bathymetry in the east coast of Qatar

Remotely sensed imagery is proving to be a useful tool in estimating water depths in coastal zones. On the other hand, many coastal zone studies in Qatar are only concerned with areas of shallow water and would easily benefit from updated bathymetric estimates. In this study, there are three significant satellites (Landsat TM, Landsat8 and Worldview3) that have been used to extract the bathymetric data from their images. We tested two different methods (1) single band algorithm and (2) principal components analysis (PCA) for extracting bathymetry information from satellite data. The location of the study area was chosen to be the east of State of Qatar. This area is called "AlGhariya" and the size of it is 62 km2. The best band in Landsat TM that can be used to extract the data as the correlation coefficient (r) value obtained by regression between the known depth and the extracted depth was the green band with a r2 value of -0.909.. The blue band and the red band were not hugely different when single band algorithm (SBA) method was used. On the another hand, the results obtained using the second method of principal components analysis (PCA) exhibited a better r2 value (0.914), which was the best result between the three satellites . The best band using the first method for Landsat 8 was found to be the red band with a r2 of -0.837. Near IR band also had a good result and relation with the known depth with -0.834. The other bands did not have a high correlation coefficient (r) value by regression between the extracted depth from the bands and the known depth. In the second method two different components of images were used. In this, the highest correlation coefficient (r) was -0.816 using blue, green and red bands. For the third satellite Worldview-3, the result was not as good as the other satellites using both methods. Using the first method, the best band was the coastal band with -0.654. The correlation coefficient (r) value was less in the blue, green, red and the other bands. The second method also was not as good for the other satellites. The highest correlation coefficient (r) was -0.641 using coastal, blue and green bands. Furthermore, the shallow waters have negative influences on the accuracy of bathymetric modeling; thus, the correction of data in these shallow waters is challenged by the presence of continental aerosols, bottom reflectance, and adjacency of land.