Overlay Index Methodology
The overlay of parameter values, representing model components, which have been rated to a suitable scale, and multiplied by respective weights, to form of an index (Shrestha, Kafle and Pandey 2017)
Shrestha, Sangam, Ranjana Kafle, and Vishnu Prasad Pandey. 2017. “Evaluation of Index-Overlay Methods for Groundwater Vulnerability and Risk Assessment in Kathmandu Valley, Nepal.” Science of the Total Environment 575: 779–90. https://doi.org/10.1016/j.scitotenv.2016.09.141.