Note: How to Use the Arc Map Editor in InfoSWMM
Step 1 is to use the Edit Feature for example the Subcatchment layer to bring up the Arc Map Editor Tool.
Step 2 is to use the Reshape Feature tool or Vertex tools to bring together mis matched Subcatchment Boundaries
Step 3 is to use save the edits and then Update the DB from the Map to recalculate the area of the Subcatchments
via Blogger http://www.swmm5.net/2013/08/how-to-use-arc-map-editor-in-infoswmm.html