Center for Watershed Protection. 2011. Illicit Discharge Detection and Tracking Guide. Center for Watershed Protection, Ellicott City, MD. IDDE, Model, planning, pollutant, tool This mini-guide contains procedures for detecting and tracking illicit discharges through a desktop assessment of illicit discharge potential, field screening of outfalls to detect illicit discharges and drainage area investigations to locate and remove the source of the discharge.