The percent developed area (PDA) is commonly used to estimate TIA manually by using maps. The Multi-Resolution Land Characteristics Consortium (MRLCC) defines a developed area as being covered by at least 30 percent of constructed materials). Southard (1986) defined non-developed areas as natural, agricultural, or scattered residential development. He developed a regression equation to predict TIA using percent developed area (table 6-1). He developed his equation using logarithmic power function with data from 23 basins in Missouri. He noted that this method was advantageous because large basins could quickly be delineated and TIA estimated manually from available maps. Granato (2010) developed a regression equation by using data from 262 stream basins in 10 metropolitan areas of the conterminous United States with drainage areas ranging from 0.35 to 216 square miles and PDA values ranging from 0.16 to 99.06 percent.