One point I often get confused on is unsteady models and flow hydrographs. I have a project that is only about a mile long but has several culverts along it that we need to analyze. Therefore the overall basin has been separated into several catchments and hydrographs created for each. My confusion is if you need to input composite hydrographs for each flow input cross section for all the contributing areas upstream (simular to what you would do for stead model) or if the system will sum the flows for individual hydrogaphs and lag them as it progresses down the model.