Iowa Stormwater Management Manual
The Iowa Stormwater Management Manual will be updated from time to time. When changes are made, the version number and date will change. A summary of the changes will also be listed.
The following infiltration-related specifications and figures (Chapter 1) have been developed to accompany the design portion (Chapter 2) of the Iowa Stormwater Management Manual.
Please note - the figures are provided in PDF, AutoCad (dwg), and Microstation (dgn) formats.
Chapter 1 - Specifications
Infiltration Practices
- Section 1E-2 - Infiltration Trenches
- Section 1E-4 - Bioretention System
- Section 1I-3 - Dry Swales
- Section 1J-2 - Pervious PCC Pavement
- Section 1J-3 - Porous HMA Pavement
- Section 1J-4 - Permeable Interlocking Concrete Pavers
Figures
- Figure 1E-2.1 - Infiltration Trench pdf dwg dgn
- Figure 1E-4.1 - Bioretention System with Engineering Fabric pdf dwg dgn
- Figure 1E-4.2 - Bioretention System with Filter Sand Layer pdf dwg dgn
- Figure 1I-3.1 - Dry Swale with Engineering Fabric pdf dwg dgn
- Figure 1I-3.2 - Dry Swale with Filter Sand Layer pdf dwg dgn
- Figure 1I-3.3 - Narrow Trench Dry Swale with Filter Sand Layer pdf dwg dgn
- Figure 1J-2.1 - Pervious PCC Pavement pdf dwg dgn
- Figure 1J-3.1 - Porous HMA Pavement pdf dwg dgn
- Figure 1J-4.1 - Permeable Interlocking Concrete Pavers pdf dwg dgn
Chapter 2 - Design
The following table of contents includes links to Version 3 (dated October 28, 2009) of Chapter 2 of the Iowa Stormwater Management Manual.
The changes made since Version 2 (dated December 5, 2008) are as follows:
- Minor correction to a calculation in Table 1 of Section 2A-4.
- Various updates to references.
- Complete new parts 2J, 2K, and 2L.
2A General Information
2A-1 General Information
- Concept
- Overview of stormwater discharges
- Pollutants in urban stormwater
- Management of stormwater quality and quantity
- Permit requirement overview
2A-2 Planning and Design Principles
- 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
- Introduction
- Regulated activities
- Requirements for regulated MS4s
- Stormwater management programs
2A-4 Stormwater Management Criteria
- Development criteria
- Minimum stormwater management guidelines
- Minor and major design storms
- Design frequencies for conveyance facilities
- Street flow criteria
2A-5 Project Drainage Report
- Purpose
- Instructions for preparing report
- Contents
2B Unified Sizing Criteria
2B-1 Unified Sizing Criteria
- 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
2C-1 General Information for Stormwater Hydrology
- Introduction
- Definitions
- Concepts
- Methods of runoff estimation
2C-2 Rainfall and Runoff Analysis
- Introduction
- Rainfall frequency analysis
- NRCS 24-hour storm distribution
2C-3 Time of Concentration
- 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
- Introduction
- Characteristics
- Limitations
- Use of the Rational method
- Design example
2C-5 NRCS TR-55 Methodology
- Introduction
- Equations and concepts
- Runoff factor
- Urban modifications of the NRCS method
- WINTR-55 for analysis
2C-6 Small Storm Hydrology
- 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
- 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
- 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
- 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
- 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
- Introduction
- Water quality
- Channel erosion control and flood control
- Design criteria
2C-12 Detention Basin Outlet Structures
- 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 grates
- Secondary outlets
2C-13 Water Balance Calculations
- Introduction
- Base equations
2C-14 Downstream Hyrologic Assessment
- Introduction
- Reasons for downstream problems
- The ten-percent rule
- Design example
2D BMP Types and Applications
2D-1 General Information for BMPs
- Description and performance of stormwater BMPs
- Goals of stormwater BMPs
- Pollutant removal processes
2D-2 Non-Structural Controls
- Education, recycling, and source controls
- Maintenance practices
2D-3 Structural Controls
- 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
2E-1 General Information for Infiltration Practices
- 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
- 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
- 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
- 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
- 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
- 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
- Definition
- Purpose
- Conditions where practice applies
- Criteria
- Additional considerations
2F Filtration Practices
2F-1 Sand Filter
- 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
- 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
- Description
- Pollutant removal capabilities
- Design criteria
- Inspection and maintenance requirements
2G Detention Practices
2G-1 General Information for Detention Practices
- Introduction
- Storage facilities
2G-2 Dry Detention
- Description
- Design criteria and physical specifications
- Inspection and maintenance requirements
- Example schematics
2G-3 Wet Detention
- Description
- Stormwater management suitability
- Pollutant removal capabilities
- Application and feasibility
- Design approach
- Design procedures
- Inspection and maintenance requirements
2H Stormwater Wetlands
2H-1 General Information for Stormwater Wetlands
- Description
- Stormwater managment suitability
- Pollutant removal capabilities
- Application and feasibility
2H-2 Design of Stormwater Wetlands
- 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
2I-1 General Information for Vegetated Swale Systems
- 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
- 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
- Description
- Stormwater management suitability
- Pollutant removal capabilities
- Applications and feasibility
- Planning and design criteria
- Design procedure
- Design example
2I-4 Vegetated Filter Strips
- Description
- Pollutant removal capabilities
- Design criteria
- Inspection and maintenance requirements
- Design example
2J Pavement Systems
2J-1 General Information for Pavement Systems
- Introduction
- General description
- Design considerations
- Permeable pavement design example
2J-2 Pervious Concrete Pavement
- General description
- Design criteria and specifications
2J-3 Porous Asphalt Pavement
- General description
- Design criteria and specifications
2J-4 Permeable Pavers
- General description
- Pollutant removal capabilities
- Design criteria and specifications
- Inspection and maintenance requirements
2K Mechanical Systems
2K-1 General Information for Proprietary Mechanical Systems
- Introduction
- Guidelines for using proprietary systems
2K-2 Hydrodynamic Devices
- 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
- 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
- Introduction
- Description
- Selection of catch basin insert filtration devices
- Applicability
- Limitations
- Siting and design considerations
- Maintenance considerations
- Effectiveness
- Cost considerations
2L Coagulation and Flocculation
2L-1 Coagulation and Flocculation
- General description
- Pollutant removal capabilities
- Design criteria and specifications
- Siting and design considerations
- Limitations
- Maintenance considerations
- Cost considerations
2M Storm Sewer Design
2M-1 General Information for Storm Sewer Design
- Introduction
- Definitions
- Location of storm sewers
- Pipe materials
- Physical requirements
- Horizontal alignment
2M-2 Groundwater Barriers and Outlets
- Introduction
- Groundwater barriers
- Outlets
2M-3 Street Flow and Intake /Manhole Capacity
- Introduction
- Definitions
- Intercepting flows
- Storm sewer structure locations
- Intake capacity
- Manhole and intake standards
- Intake capacity design example
2M-4 Storm Sewer Sizing
- Introduction
- Flow formulas
- Hydraulic losses
- Hydraulic design of storm sewers
2N Design of Culverts
2N-1 General Information for Design of Culverts
- 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
- Culvert flow controls and equations
- Inlet and outlet control
- Use of inlet and outlet control nomographs
- Culvert design example
2O Open Channel Flow
2O-1 Channel Types and Structures
- Introduction
- Channel types
- Drop structures for open channel flow
2O-2 Open Channel Flow
- Introduction
- Definitions
- Uniform flow (Manning's equation)
- Energy flow
- Non-uniform flow
- Hydraulic jump
- Hydraulic jump design example for trapezoidal channel
- Solution nomographs