Impervious Surfaces from High Resolution Aerial Imagery: Cities in Fresno County

Impervious surfaces are landscapes covered by material with little or no water permeability, such as pavement, sidewalks, parking lots, and other hard surfaces. Impervious surfaces prevent water from being absorbed into the ground, which can lead to a number of environmentally negative impacts, such as flooding, erosion and pollution of streams, and waterways. An impervious surface study involves mapping and analyzing the extent and distribution of impervious surfaces within the study areas such as cities, counties, census tracts, etc. The study typically uses remote sensing data - satellites/aerial imagery, to identify and classify impervious surfaces. Fresno County was classified and assessed using pixel-based, object-based, and deep-learning classification. The deep learning classification outperforms in classification accuracy assessment, showing 85-92% overall accuracy. The analysis of percent impervious surfaces in cities in Fresno County is estimated to be 45% which is equivalent to that of medium-density residential areas. For the Fresno/Clovis city area, the percent impervious surface increased from 53% in 2010 (EnviroAtlas) to 63% in 2020. This 10% increase in 10 years is aligned well with the population increase.