This paper describes a methodology to estimate permeable and impermeable areas in consolidated urban areas based on satellite image analysis and field survey. The methodology allows inventorying vegetated cover and potential permeable areas that are actually not effective to reduce runoff due to lack of urban drainage management practices. It includes the selection of the parameters, definition and distribution of the sample units, definition of the sample size, and design of the field work protocol to collect information. This methodology was applied to an urban subcatchment in Barranquilla, Colombia. Based on the satellite images 52% of the area was identified as permeable and 48% as impermeable. In contrast, based on the field survey the effective permeable area was reduced to 27% increasing the effective impermeable area to 73%. These results showed that with only the satellite image analysis the permeable area is overestimated, underestimating the runoff coefficient. Therefore, an structured methodology to identify and estimate ineffective permeable areas is required for consolidated urban areas. This analysis allows performing a diagnosis oriented to define a more realistic starting point for urban watershed retrofitting with sustainable urban drainage systems.