Micro Drainage is a modeling methodology for analyzing surface and sewer drainage system performance. Micro Drainage models precipitation flowing from overland systems into minor systems through catchbasins acting as outlets from major to minor systems. This technique model everything from overland cross-sections, culverts, inlet/onsite controls, to inlet blockages, and more. Thus, by modeling at the “micro” level, the accuracy of the model will greatly increase and produce more accurate present and post-development conditions.

This tool simplifies the analysis of the catchment drainage system using improved details and accounts for blockage. Micro Drainage analysis is a method for improving municipal and watershed drainage analysis through the combined use of drainage system asset data, surface topographic, other geographic data, and GIS techniques, and hydrologic and hydraulic computational engines. Some of the details captured by the models are:

• Major System (overland flow) cross-sections, road types and shape of pipe in the minor system;
• Lead (outlet from major to the minor system) size;
• The type of catchbasins to use in the model (fishbone, dual basins, etc.);
• The slope of the major and minor links;
• The roughness of the land/pipes;
• Any on-site, and inlet control devices;
• Ponds and Sag (storage) areas;
• Inlet / Catchbasins blockage;
• Impervious areas (roofs, roads, etc.) for each delineated catchment; and,
• Roofs that are directly connected to storm sewers.