COURSE DESCRIPTION

This course teaches you how to use AGWA's Detention Basin Workflow to evaluate the stormwater management performance of one or more detention basins. The workflow combines external basin routing results from a tool such as HydroCAD or HEC-HMS with AGWA's GSSHA-based watershed simulation to show how a proposed or existing detention pond changes downstream discharge at user-defined output locations.

This is a hybrid modeling approach: you route flow through the basin in a dedicated pond routing tool, supply pre- and post-basin hydrographs to AGWA, and AGWA substitutes the routed outflow into the GSSHA channel network to compute downstream results.

Prerequisite: the Find Discharge Workflow course is strongly recommended before taking this course. The Detention Basin Workflow uses the same model selection, scenario selection, and results review interface, and adds basin polygon, outlet, and hydrograph input steps on top of that foundation.

Estimated time: approximately 75 minutes reading; up to 2 hours with hands-on hydrograph preparation and workflow practice.

Recommended browser: Chrome.

LEARNING OBJECTIVES

Upon completing this course, you will be able to:

• Explain the uncoupled modeling approach and why detention routing is performed outside GSSHA.
• Identify the assumptions, limitations, and situations in which the workflow should not be used — including the critical ponds-in-series case.
• Prepare pre- and post-basin hydrographs using HydroCAD, HEC-HMS, or a spreadsheet in the correct format for AGWA entry.
• Execute all seven steps of the workflow: upload basin polygons, define outlets, select scenarios, enter pre-basin hydrographs, enter post-basin hydrographs, place output locations, and run the simulation.
• Interpret pre/post discharge comparison tables and hydrograph overlays to evaluate basin performance across multiple design storm scenarios.
• Recognize result warning signs that indicate input errors and know how to resolve them.
• Export results and produce a complete, professionally structured engineering report.