Spectral Reflectance of Kelantan Estuary with ALOS Data to Estimate Transparency

The Kelantan estuary, located in the northeastern part of Peninsular Malaysia, is characterized by high levels of suspended sediments. Kuala Besar is the estuary of the river directly opposite South China Sea. Spectral reflectance (Rr) and transparency measurements were carried out in the Kelantan estuary. The objective in this study is to establish empirical relationships between spectral remote sensing reflectance in ALOS satellite imagery and water column transparency, i.e. nephelometric turbidity unit (NTU) and Secchi disc depth (SDD) through these numerous in situ measurements. We detected that remote sensing reflectance are linear and power regression functions against NTU and SDD. The results of this sampling show that the wavelengths range from 500-620 nm is the most suitable band for measuring water column transparency. The calibrated reflectance of ALOS AVNIR-2 bands was also regressed against NTU and SDD field data to derive two empirical equations for water transparency estimation. These equations were calculated using ALOS images data on June 12, 2010. The result obtained indicated that reliable estimates of turbidity and transparency values for the Kelantan Estuary, Malaysia, could be retrieved using this method.