The Iowa Stormwater Management Manual (ISWMM) has been assembled to provide guidance and resources to local jurisdictions (cities, counties, etc.) that adopt ordinances or policies which set requirements for stormwater management. The manual also provides guidance on properly sizing and designing post construction practices for consultants and plan reviewers. The practices described in the manual are not requirements of the DNR. For more information about the manual, including resources for local jurisdictions, designers, and reviewers, and additional planning and design resources, read more about the manual.
We are currently transitioning the ISWMM into a new format and table of contents. The new format, which may have new numbers and/or titles, is shown on the left side of the following table. The old format is shown on the right side. The new and old corresponding sections are aligned horizontally to each other. Sections titles are linked to the most current version of the manual.
| New ISWMM Format | Old ISWMM Format |
|---|---|
| 1.01 Stormwater Basics | Ch 1 Sec 1 General Information |
| 1.02 Planning and Design Principles | Ch 1 Sec 2 Planning and Design Principles |
| 1.03 Stormwater Regulations and Permitting | Ch 1 Sec 3 Stormwater Regulations and Permitting |
| 1.04 Stormwater Management Criteria | Ch 1 Sec 4 Stormwater Management Criteria |
| 1.05 Stormwater Management Plan | Ch 1 Sec 5 Project Drainage Report |
| 2.01 Overview of Stormwater Hydrology | Ch 3 Sec 1 General Information for Stormwater Hydrology |
| 2.02 Rainfall and Runoff Analysis | Ch 3 Sec 2 Rainfall and Runoff Analysis |
| 2.03 Time of Concentration | Ch 3 Sec 3 Time of Concentration |
| 2.04 Rational Method (abbreviated) | Ch 3 Sec 4 Rational Method |
| 2.05 NRCS TR-55 Methodology | Ch 3 Sec 5 NRCS TR-55 Methodology |
| 2.06 Runoff Hydrograph Determination | Ch 3 Sec 7 Runoff Hydrograph Determination |
| 2.07 LID Hydrology | Ch 3 Sec 8 LID Hydrology |
| 3.01 Unified Sizing Criteria | Ch 2 Sec 1 Unified Sizing Criteria |
| 3.02 Small Storm Hydrology | Ch 3 Sec 6 Small Storm Hydrology |
| 4.01 Introduction to BMPs | Ch 4 Sec 1 General Information for BMPs |
| 4.02 Non-structural BMPs | Ch 4 Sec 2 Non-structural BMPs |
| 4.03 Selecting Structural BMPs | Ch 4 Sec 3 Structural BMPs |
| 5.01 Pretreatment Practices | No previous chapter |
| 5.02 Grass Swales | Ch 9 Sec 1 General Information for Vegetated Swale Systems** |
| Ch 9 Sec 2 Grass Swales** | |
| Ch 9 Sec 3 Dry and Wet Swales** | |
| 5.03 Vegetative Filter Strip | Ch 9 Sec 4 Vegetative Filter Strips |
| 5.04 Sediment Forebay | Ch 3 Sec 11 Inlet Sediment Forebays |
| 5.05 Hydrodynamic Devices | Ch 11 Sec 1 General Information for Proprietary Mechanical Systems* |
| Ch 11 Sec 2 Hydrodynamic Devices | |
| 5.06 Gravity Separators | Ch 11 Sec 3 Gravity Separators |
| Ch 11 Sec 4 Catch Basin Sumps and Inserts | |
| 6.01 Rainfall Collection and Reuse BMPs | No previous chapter |
| 6.02 Green Roofs | Ch 17 Green Roof Systems |
| 6.03 Rainwater Harvesting | No previous chapter |
| 7.01 Infiltration BMPs | Ch 5 Sec 1 General Information for Infiltration Practices |
| 7.02 Soils Testing Requirements for Infiltration Practices | Ch 5 Sec 8 Soils Testing Requirements for Infiltration Practices |
| 7.03 Soil Quality Management and Restoration | Ch 5 Sec 6 Soil Quality Management and Restoration |
| 7.04 Tree Filter Systems | No previous chapter |
| 7.05 Infiltration Trenches | Ch 5 Sec 2 Infiltration Trenches |
| Ch 5 Sec 4 Bioretention Systems | |
| 7.07 Bioswales | Ch 5 Sec 5 Bioswales |
| 7.08 Infiltration Basins | Ch 5 Sec 3 Infiltration Basins |
Bioretention Design Checklists: | |
| 8 Permeable Pavement Systems | Ch 10 Sec 1 General Information for Permeable Pavement Systems** |
| Ch 10 Sec 2 Pervious Concrete Pavement** | |
| Ch 10 Sec 3 Porous Asphalt Pavement** | |
| Ch 10 Sec 4 Permeable Pavers** | |
Supporting Documentation Checklists: | |
| 9.01 Stormwater Detention BMPs | Ch 7 Sec 1 General Information for Detention Practices |
| 9.02 Methods to Estimate Required Detention Storage | Ch 3 Sec 9 Detention Storage Design |
| 9.03 Storage Routing for Final Detention Design | Ch 3 Sec 10 Channel and Reservoir Routing* |
| 9.04 Design and Modeling of Outlet Controls | Ch 3 Sec 12 Detention Basin Outlet Structure |
| 9.05 Water Balance Calculations | Ch 3 Sec 13 Water Balance Calculations |
| 9.06 Channel Routing | Ch 3 Sec 10 Channel and Reservoir Routing* |
| 9.07 Downstream Hydrologic Assessment | Ch 3 Sec 14 Downstream Hydrologic Assessment |
| 9.08 Constructed Stormwater Wetlands | Ch 8 Sec 1 General Info for Stormwater Wetlands** |
| Ch 8 Sec 2 Design of Stormwater Wetlands** | |
| 9.09 Traditional Dry Detention | Ch 7 Sec 2 Dry Detention* |
| 9.10 Extended Dry Detention | Ch 7 Sec 2 Dry Detention* |
| 9.11 Wet Ponds | Ch 7 Sec 3 Wet Detention |
| 9.12 Detention Retrofits | No previous chapter |
| 9.13 Underground Detention | No previous chapter |
| 9.14 Glossary | No previous chapter |
Design Review Checklists: | |
| Supporting Documentation Checklist | |
| 10.01 Sand Filter BMPs | Ch 6 Sec 1 Sand Filter |
| 10.02 Surface and Perimeter Sand Filter | Ch 6 Sec 2 Design of Surface and Perimeter Sand Filter |
| 10.03 Underground Sand Filter | Ch 6 Sec 3 Underground Sand Filter |
| 11 Native Landscaping | Ch 5 Sec 7 Native Landscaping |
| 12 Regenerative Conveyance | Ch 15 Sec 1 Channel Types and Structures** |
| Ch 15 Sec 2 Open Channel Flow** | |
| 13 References | Ch 18 References |
ISWMM Design Standards Specifications
Old Format Notations:
* Old chapter to be split into separate chapters in new format
** Old chapters integrated into one chapter in new format