Stormwater management ordinances focused on detention requirements for flood control are at paradigm step 5. Flood flows occur when the water rises above the streambanks following larger rainfalls or in combination with snowmelt or ice jams. Controlling flood flows and regulating development in the floodway and floodplain are important for the protection of lives and property.

Adding water quality requirements moves the ordinance to paradigm step 6. Pollutant concentrations in stormwater runoff tend to decrease with time during larger storms. Thus treating the "first flush" of the runoff, often defined as 0.5" of runoff, is often a requirement. First flush sizing criteria generally is only effective for a single site. For multible sites or watershed wide design it is best to design to capture and treat 90% of the runoff producing storms. This "90% rule" effectively treats storm runoff that could be reaching the treatment at different times during the storm event. It was designed to provide the greatest amount of treatment that is economically feasible.

Adding channel protection criteria to prevent accelerated erosion moves the ordinance up to paradigm step 7. Channel-forming flows are the flows that control the channel shape. The stream channel responds to increases in these flows by widening and deepening, which becomes apparent by increased erosion. In a morphologically stable stream, Channel-forming flows will be bankfull flows and have a recurrence interval of 1 to 2 years on average. Controlling these flows protects the upstream channel reaches from extensive, excessive erosion and downstream reaches from increased sediment deposition. Controlling the duration of the channel-forming flows may be as important as controlling the peak flow. Exposing the streambanks to bankfull flows for longer time periods can also weaken the streambanks.

Paradigm step 8 occurs when political entities within a watershed scale integrate and coordinate stormwater management.

Paradigm step 9 occurs when local governments incorporate proven low impact Best Management Practices (BMPs), such as rain gardens, green roofs, grass swales, infiltration basins, etc., throughout the watershed to maintain consistent ecologic conditions.

Limiting flooding requires managing runoff from large storms

Managing water quality typically involves treating the first flush of stormwater runoff

Protecting the channel from increased erosion involves controlling the channel-forming flows and volumes