Iowa Stormwater Management Manual
The following table of contents includes links to Version 2 (dated December 5, 2008) of the Iowa Stormwater Management Manual. The manual will be updated from time to time as review of the text and sample problems take place. Some sections remain to be developed.
The changes made since Version 1 (dated February 19, 2007) are as follows:
- Minor correction to an equation in Section 2C-5 (NRCS TR-55 Method).
- Various revisions to Part 2M (Storm Sewer Design) to correspond with changes made in the 2009 Edition of the SUDAS Standard Specifications.
All the documents are pdf files.
2A General Information 345 kb
2A-1 General Information 73 kb pdf
- Concept
- Overview of stormwater discharges
- Pollutants in urban stormwater
- Management of stormwater quality and quantity
- Permit requirement overview
2A-2 Planning and Design Principles 176 kb pdf
- Project scope and analysis
- Developing a stormwater management plan
- Planning and design principles
- Planning and design conditions
- Floodplain management
2A-3 Stormwater Regulations and Permitting 63 kb pdf
- Introduction
- Regulated activities
- Requirements for regulated MS4s
- Stormwater management programs
2A-4 Stormwater Management Criteria 53 kb pdf
- Development criteria
- Minimum stormwater management guidelines
- Minor and major design storms
- Design frequencies for conveyance facilities
- Street flow criteria
2A-5 Project Drainage Report 49 kb pdf
- Purpose
- Instructions for preparing report
- Contents
2B Unified Sizing Criteria 192 kb
2B-1 Unified Sizing Criteria 192 kb pdf
- General information
- Rainfall frequency spectrum (RFS)
- Water quality volume (WQv)
- Recharge volume requirements (Rev)
- Channel protection storage volume requirements (CPv)
- Overbank flood protection volume requirements (Qp)
- Extreme flood volume (Qf)
2C Stormwater Hydrology 6.99 mb
2C-1 General Information for Stormwater Hydrology 139 kb pdf
- Introduction
- Definitions
- Concepts
- Methods of runoff estimation
2C-2 Rainfall and Runoff Analysis 188 kb pdf
- Introduction
- Rainfall frequency analysis
- NRCS 24-hour storm distribution
2C-3 Time of Concentration 312 kb pdf
- Introduction
- Definition
- Factors affecting time of concentration
- Estimating time of concentration (NRCS velocity method)
- Estimating time of concentration (NRCS lag method)
- Design example
2C-4 Rational Method 134 kb pdf
- Introduction
- Characteristics
- Limitations
- Use of the Rational method
- Design example
2C-5 NRCS TR-55 Methodology 381 kb pdf
- Introduction
- Equations and concepts
- Runoff factor
- Urban modifications of the NRCS method
- WINTR-55 for analysis
2C-6 Small Storm Hydrology 281 kb pdf
- Introduction
- Water quality volume and peak flow
- Method for computing the channel protection storage volume
- Maximized water quality capture volume
- Estimating a maximized water quality capture volume
- Design example
2C-7 Runoff Hydrograph Determination 1.12 mb pdf
- Introduction
- Unit hydrographs
- Application of the unit hydrograph method
- Watershed routing (hydrograph determination)
- Tabular hydrograph method
- Design example
2C-8 Low-Impact Development (LID) Hydrology 2 mb pdf
- Introduction
- Hydrologic comparison: conventional vs. low-impact development
- LID hydrologic analysis components
- Process and computational procedure
- Determination of design storm event
2C-9 Detention Storage Design 182 kb pdf
- Introduction
- Alternatives for estimating detention volume
- Planning and design alternatives
- Preliminary detention storage design
- Modified Rational method
- Design example
2C-10 Channel and Storage (Reservoir) Routing 466 kb pdf
- Introduction
- Channel routing
- Storage (reservoir) routing
- Stage-storage relationship
- Stage-discharge relationship
- Storage-indication routing
- Detention design procedure with storage routing
- Design example (currently under development)
2C-11 Inlet Sediment Forebays 269 kb pdf
- Introduction
- Water quality
- Channel erosion control and flood control
- Design criteria
2C-12 Detention Basin Outlet Structures 2.17 mb pdf
- Introduction
- Outlet structure types
- Extended detention (water quality and channel protection) outlet design
- Sizing of single-stage risers
- Design of multiple stage outlets
- Extended detention outlet protection
- Trash racks and safety gates
- Secondary outlets
2C-13 Water Balance Calculations 78 kb pdf
- Introduction
- Base equations
2C-14 Downstream Hyrologic Assessment 178 kb pdf
- Introduction
- Reasons for downstream problems
- The ten-percent rule
- Design example
2D BMP Types and Applications 276 kb
2D-1 General Information for BMPs 27 kb pdf
- Description and performance of stormwater BMPs
- Goals of stormwater BMPs
- Pollutant removal process
2D-2 Non-Structural Controls 20 kb pdf
- Education, recycling, and source controls
- Maintenance practices
2D-3 Structural Controls 263 kb pdf
- Structural BMPs
- Structural control categories
- Structural stormwater control pollutant removal capabilities
- Selection guide for structural stormwater controls
- General application control screening process
- Online vs. off-line structural controls
- Onsite vs. regional stormwater management
- Using structural stormwater controls in series
2E Infiltration Practices 5.19 mb
2E-1 General Information for Infiltration Practices 220 kb pdf
- Introduction
- Infiltration fundamentals
- Infiltration systems
- Infiltration hydraulics and process
- Soils and infiltration
- Screening criteria for infiltration practices
- Types of infiltration practices
- Design criteria for infiltration practices
2E-2 Infiltration Trenches 1.6 mb pdf
- Description
- Stormwater management suitability
- Pollutant removal capabilities
- Application and feasibility
- Planning and design criteria
- Physical specifications, geometry, and volume
- Design of infiltration trenches
- Design procedures
- Inspection and maintenance requirements
- Example schematics
- Design example
2E-3 Infiltration Basins 1.8 mb pdf
- Description
- Stormwater management suitability
- Pollutant removal capabilities
- Application and feasibility
- Planning and design criteria
- General design
- Physical specifications, geometry, and volume
- Design of infiltration basins
- Procedures for infiltration basin design
- Maintenance
- Design example
2E-4 Bioretention Systems 1.7 mb pdf
- Description
- Stormwater management suitability
- Pollutant removal capabilities
- Application and feasibility
- Planning and design criteria
- Physical specifications and geometry
- Structures
- Design procedures
- Inspection and maintenance requirements
- Design example
2E-5 Soil Quality Restoration 202 kb pdf
- Description
- Stormwater management suitability
- Pollutant removal capabilities
- Application and feasibility
- Planning and design criteria
- Design procedures
- Inspection and maintenance requirements
- Design example
2E-6 Native Landscaping 149 kb pdf
- Description
- Stormwater management suitability
- Pollutant removal capabilities
- Application and feasibility
- Planning and design criteria
- Design procedures
- Inspection and maintenance requirements
2E-7 Soils Testing Requirements for Infiltration Practices 125 kb pdf
- Definition
- Purpose
- Conditions where practice applies
- Criteria
- Additional considerations
2F Filtration Practices 2.0 mb
2F-1 Sand Filter 1.1 mb pdf
- Description
- Stormwater management suitability
- Pollutant removal capabilities
- Application and feasibility
- Planning and design criteria
- Flow regulation
2F-2 Design of Surface and Perimeter Sand Filter 747 kb pdf
- Physical specifications and geometry
- Pre-treatment/inlets
- Outlet structures
- Auxiliary spillway
- Maintenance access
- Safety features
- Landscaping
- Additional site-specific design criteria and considerations
- Design procedures
- Inspection and maintenance requirements
- Design example
2F-3 Underground Sand Filter 303 kb pdf
- Description
- Pollutant removal capabilities
- Design criteria
- Inspection and maintenance requirements
2G Detention Practices 2.3 mb
2G-1 General Information for Detention Practices 267 kb pdf
- Introduction
- Storage facilities
2G-2 Dry Detention 866 kb pdf
- Description
- Design criteria and physical specifications
- Inspection and maintenance requirements
- Example schematics
2G-3 Wet Detention 1.3 mb pdf
- Description
- Stormwater management suitability
- Pollutant removal capabilities
- Application and feasibility
- Design approach
- Design procedures
- Inspection and maintenance requirements
2H Stormwater Wetlands 1.02 mb
2H-1 General Information for Stormwater Wetlands 1 mb pdf
- Description
- Stormwater managment suitability
- Pollutant removal capabilities
- Application and feasibility
2H-2 Design of Stormwater Wetlands 75 kb pdf
- Planning and design criteria
- General design
- Physical specifications and geometry
- Pre-treatment inlets
- Outlet structures
- Auxiliary spillway
- Maintenance access
- Safety features
- Landscaping
- Additional site-specific design criteria and issues
- Design procedures
- Inspection and maintenance requirements
2I Vegetated Swale Systems 2.02 mb
2I-1 General Information for Vegetated Swale Systems 497 kb pdf
- Introduction
- Types of vegetated practices
- Comparative pollutant removal capability
- Suitability and selection considerations
- Land use factors
- Site conditions
- Flow regulation
- Pre-treatment
2I-2 Grass Swales 807 kb pdf
- Description
- Stormwater management suitability
- Pollutant removal capabilities
- Application and feasibility
- Grass swales for pre-treatment
- Check dams
- Channel design criteria
- Design procedure
- Inspection and maintenance requirements
- Design example
2I-3 Dry and Wet Swales 718 kb pdf
- Description
- Stormwater management suitability
- Pollutant removal capabilities
- Applications and feasibility
- Planning and design criteria
- Design procedure
- Design example
2I-4 Vegetated Filter Strips 320 kb pdf
- Description
- Pollutant removal capabilities
- Design criteria
- Inspection and maintenance requirements
- Design example
2J Pavement Systems 3.16 mb
2J-1 General Information for Pavement Systems 1.17 mb pdf
- Introduction
- General description
- Design considerations
- Permeable pavement design example
2J-2 Pervious Concrete Pavement 969 kb pdf
- General description
- Design criteria and specifications
2J-3 Porous Asphalt Pavement 981 kb pdf
- General description
- Design criteria and specifications
2J-4 Permeable Pavers 178 kb pdf
- General description
- Pollutant removal capabilities
- Design criteria and specifications
- Inspection and maintenance requirements
2K Mechanical Systems 316 kb pdf
2K-1 General Information for Proprietary Mechanical Systems 24 kb pdf
- Introduction
- Guidelines for using proprietary systems
2K-2 Hydrodynamic Devices 119 kb pdf
- Description
- Applicability
- Continuous deflective separation (CDS)
- Downstream defender
- Stormceptor
- Vortechs
- Advantages and disadvantages
- Performance
- Water quantity control
- Cold climate
- Operation and maintenance
- Costs
2K-3 Gravity Separator Systems 163 kb pdf
- General description
- Pollutant removal capabilities
- Design criteria and specifications
- Inspection and maintenance requirements
- Additional maintenance considerations and requirements
2K-4 Catch Basins with Sumps and Catch Basin Inserts 55 kb pdf
- Introduction
- Description
- Selection of catch basin insert filtration devices
- Applicability
- Limitations
- Siting and design considerations
- Maintenance considerations
- Effectiveness
- Cost considerations
2L Coagulation and Flocculation 87 kb
2L-1 Coagulation and Flocculation 87 kb pdf
- General description
- Pollutant removal capabilities
- Design criteria and specifications
- Siting and design considerations
- Limitations
- Maintenance considerations
- Cost considerations
2M Storm Sewer Design 643 kb
2M-1 General Information for Storm Sewer Design 66 kb pdf
- Introduction
- Definitions
- Location of storm sewers
- Pipe materials
- Physical requirements
- Horizontal alignment
2M-2 Groundwater Barriers and Outlets 67 kb pdf
- Introduction
- Groundwater barriers
- Outlets
2M-3 Street Flow and Intake /Manhole Capacity 328 kb pdf
- Introduction
- Definitions
- Intercepting flows
- Storm sewer locations
- Intake capacity
- Manhole and intake standards
- Intake capacity design example
2M-4 Storm Sewer Sizing 353 kb pdf
- Introduction
- Flow formulas
- Hydraulic losses
- Hydraulic design of storm sewers
2N Design of Culverts 1.36 mb
2N-1 General Information for Design of Culverts 193 kb pdf
- Introduction
- Definitions
- Site considerations
- Culvert design items
- Design considerations
- Pipe material
- Pipe culvert sizes
- Culvert inlets
- Roadway or street overtopping
- Storage routing
2N-2 Culvert Hydraulics 1.2 mb pdf
- Culvert flow controls and equations
- Inlet and outlet control
- Use of inlet and outlet control nomographs
- Culvert design example
2O Open Channel Flow 508 kb
2O-1 Channel Types and Structures 62 kb pdf
- Introduction
- Channel types
- Drop structures for open channel flow
2O-2 Open Channel Flow 459 kb pdf
- Introduction
- Definitions
- Uniform flow (Mannings Equation)
- Energy flow
- Non-uniform flow
- Hydraulic jump
- Hydraulic jump design example for trapezoidal channel
- Solution nomographs