Learn Drainage Design
Follow a structured pathway or browse every published article by topic.
This library connects hydrology, hydraulics, codes, and field applications for homeowners, contractors, students, and engineers. Article cards are generated from the same content collection that supplies each published page, so new material cannot silently disappear from this index.
Start with the fundamentals
Learning Pathways
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Drainage Design 101
Start here — learn the fundamentals of how water moves and how to design drainage systems.
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1. How Drainage Works
8 min readUnderstand why water collects and how drainage systems move it.
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2. Understanding Runoff
6 min readLearn how rainfall becomes runoff and what affects how much you get.
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3. The Rational Method
10 min readThe most common way to calculate how much water you need to handle.
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5. Choosing a Solution
7 min readFrench drains, rain gardens, catch basins — which one fits your situation?
Stormwater Management
Learn how to manage stormwater with modern green infrastructure approaches.
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1. Curve Number Method
10 min readA more detailed way to estimate runoff for larger or more complex sites.
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2. Time of Concentration
8 min readHow long it takes water to travel across your site — critical for sizing.
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3. Reading Hydrographs
6 min readUnderstanding flow over time, not just peak values.
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All 49 Articles
Fundamentals
Core hydrology and drainage principles.
Drainage Design 101: A Complete Introduction
Learn the fundamentals of stormwater drainage design, from basic hydrology concepts to practical engineering applications.
Understanding and Reading Hydrographs
Learn how to interpret hydrographs, understand their components, and apply hydrograph analysis to stormwater design.
Methods
Calculation methods used in drainage engineering.
Manning's Equation Explained: A Complete Guide
Master Manning's Equation for open channel and pipe flow calculations. Learn the theory, n-value selection, applications to pipes and channels, and practical worked examples.
SCS/NRCS Curve Number Method Explained
Comprehensive guide to the SCS Curve Number method for runoff estimation. Learn CN selection, calculation procedures, and when to use this method over the Rational Method.
Selecting the Right Design Storm: Return Period and Duration Guide
Learn how to select appropriate design storm return periods for different drainage applications. Understand risk, consequences, and regulatory requirements for storm event selection.
The Rational Method Explained: A Complete Guide
Master the Rational Method for peak flow estimation. Learn the theory, equation derivation, runoff coefficients, limitations, and practical applications.
Time of Concentration: Formulas & Worked Examples
Calculate time of concentration with a full worked TR-55 example (sheet, shallow, channel flow) plus the Kirpich, FAA airport, and Kerby formulas compared.
Hydraulics
Flow behavior in pipes, channels, and hydraulic structures.
Introduction to Open Channel Flow
Learn the fundamentals of open channel flow hydraulics including uniform flow, critical flow, flow classification, and practical applications.
Open Channel Design Guide for Stormwater Conveyance
How to design open channels and ditches for stormwater: channel types, Manning's sizing method, velocity and erosion limits, and practical design criteria.
Open Channel Hydraulics: Manning's Equation and Energy Concepts
A deeper dive into open channel hydraulics theory including Manning's equation derivation, hydraulic radius, energy grade line, and practical design applications.
Design
Planning and design workflows for drainage systems.
Applications
Practical guidance for common drainage applications.
Infrastructure
Guidance for public and site drainage infrastructure.
Roadway Drainage Design: Inlets, Gutters & Storm Drains
Free guide to roadway drainage design: gutter spread, inlet spacing, sag inlets, storm drain sizing, and HEC-22 methods with a worked gutter-capacity example.
Storm Drain Systems: Components and How They Work
Overview of storm drain system components including inlets, pipes, manholes, junctions, and outfalls — how each part works together.
Site Drainage
Diagnosis and solutions for drainage around a property.
Building Systems
Roof, foundation, and building drainage guidance.
Flat Roof Drainage Design Guide
Guide to flat and low-slope roof drainage design, including drain placement, overflow protection, sizing methods, and code requirements.
Roof Drainage Sizing: Gutters, Downspouts & Scuppers
How to size roof drainage: gutters, downspouts, roof drains, and scupper overflow outlets using IPC tables and design rainfall. Free calculators included.
Homeowner Guide
Plain-language guides for residential drainage decisions.
Basement Waterproofing: Drainage Solutions That Work
Fix basement water problems with proper drainage. Interior and exterior solutions, sump pumps, cost comparison, and when to hire a professional.
Driveway Drainage Solutions: Fix Pooling & Size a Drain
Stop water pooling on your driveway. Compare channel drains, trench drains, catch basins, and swales, then size a driveway drain, with costs and DIY tips.
French Drain Installation: A Complete Guide
Step-by-step French drain installation guide for homeowners. Materials, costs, common mistakes, maintenance tips, and when to hire a professional.
How Much Does a French Drain Cost?
Realistic French drain cost breakdown: materials, labor, DIY vs. professional pricing per linear foot. Cost-saving tips and when to hire a contractor.
How to Read a Drainage Plan
Learn to read drainage plans, grading plans, and site plans. Understand contour lines, spot elevations, pipe symbols, slopes, and common abbreviations.
How to Size Gutters and Downspouts for Your House
Complete guide to gutter and downspout sizing. Capacity tables, step-by-step sizing method, common problems, material comparison, and cost estimates.
Rain Garden Design for Beginners
Complete beginner's guide to rain garden design. Sizing, plant selection, step-by-step construction, maintenance, and cost estimates for homeowners.
Residential Drainage Basics: A Homeowner's Guide
Understand residential drainage problems and solutions. Learn about grading, French drains, sump pumps, downspout management, and when to call a professional.
Understanding Your Soil Type (Without a Lab Test)
Three simple home soil tests to determine your soil type for drainage projects. Ribbon test, jar test, and percolation test with interpretation guides.
When to DIY vs. Hire a Contractor for Drainage
Honest guide to which drainage projects you can do yourself and which need a professional. Decision matrix, cost comparison, and tips for finding a contractor.
Why Is My Yard Always Wet? (And How to Fix It)
Diagnose and fix a soggy yard. Learn the common causes of standing water, drainage solutions for homeowners, cost estimates, and when to hire a professional.
Contractor Guide
Field and client guidance for drainage contractors.
Common Drainage Design Mistakes (and How to Avoid Them)
10 most common drainage design and installation mistakes contractors make. Undersized pipes, wrong slopes, missing filter fabric, and how to prevent failures.
How to Use This Site to Generate Client Proposals
Step-by-step guide for drainage contractors to create data-backed proposals using free calculators. Proposal template, pricing tips, and workflow examples.
Material Comparison Guide: PVC vs. HDPE vs. Corrugated
Detailed comparison of drainage pipe materials: PVC, HDPE, and corrugated. Flow capacity, cost, durability, and when to use each type.
Quick Field Sizing: Pipe and Catch Basin Reference
Quick-reference pipe sizing, catch basin spacing, slope requirements, and runoff coefficients for drainage contractors. Print-friendly field guide.
Stormwater Compliance Checklist
Practical stormwater compliance checklist for drainage contractors. NPDES permits, erosion control BMPs, inspection requirements, and common violation fines.
Walkthrough
Worked scenarios that connect inputs, methods, and results.
Scenario Walkthroughs: Real-World Drainage Problems
Step-by-step drainage calculator walkthroughs for real-world scenarios. Pre-filled examples with explanations for homeowners and contractors.
Scenario: Building a Rain Garden for a Downspout
Step-by-step rain garden sizing walkthrough for a roof downspout. Pre-filled calculator with planting tips, cost estimates, and construction guidance.
Scenario: Detention Pond for a Small Development
Step-by-step detention pond sizing walkthrough for a 5-acre residential subdivision. Pre-filled calculator with outlet structure sizing and regulatory guidance.
Scenario: Drying Out a Soggy Side Yard
Step-by-step French drain sizing walkthrough for a narrow, muddy side yard. Pre-filled calculator with material quantities and cost estimates.
Scenario: Grading a Swale Along a Property Line
Step-by-step swale design walkthrough for intercepting neighbor's runoff. Pre-filled calculator with grading details and construction steps.
Scenario: How Long Does Runoff Take to Reach the Outlet?
Step-by-step time of concentration walkthrough using the Kirpich method for a residential watershed. Pre-filled calculator with result interpretation.
Scenario: Runoff Estimate for a Mixed-Use Site
Step-by-step SCS Curve Number walkthrough for a 10-acre mixed-use development. Weighted CN calculation, runoff volume, and detention requirements.
Scenario: Selecting a Catch Basin for a Parking Lot
Step-by-step catch basin sizing walkthrough for a commercial parking lot. Grate selection, clogging factors, and outlet pipe sizing with pre-filled calculator.
Scenario: Sizing Drainage for a Suburban Backyard
Step-by-step walkthrough using the Rational Method Calculator to size drainage for a flooding backyard. Pre-filled example with result interpretation.
Scenario: Sizing Drains for a Flat Commercial Roof
Step-by-step roof drain sizing walkthrough for a 20,000 sq ft commercial building. Drain count, size selection, overflow protection, and leader pipe sizing.
Scenario: Will This 6-Inch Pipe Handle My Runoff?
Step-by-step walkthrough checking if an existing 6-inch pipe can handle increased runoff. Manning's equation example with pre-filled calculator.
Standards & Codes
Source-aware explanations of drainage requirements.
BS EN 752 Explained: Drain and Sewer Systems Outside Buildings
A UK and European guide to BS EN 752, how it differs from Approved Document H and BS EN 12056, and how it relates to adoptable sewers, gradients, velocities and design return periods.
UK Building Regulations Part H: Drainage Falls & Gradients
A practical guide to Approved Document H of the UK Building Regulations: minimum pipe gradients for foul and surface water drainage, self-cleansing velocity, invert levels, a gradient table and a worked example.
Reference
Selection guides and supporting technical references.
Hydrologic Soil Groups: A Complete Guide
Learn how to identify and use hydrologic soil groups (A, B, C, D) for drainage calculations. Includes guidance on using NRCS Web Soil Survey and interpreting dual soil groups.
Manning's n Selection Guide: Roughness Value Tables
How to choose Manning's roughness coefficient for pipes, channels, and streams. Includes n value tables, composite-n calculation, and roughness factors.
Runoff Coefficients: A Complete Selection Guide
Comprehensive guide to selecting runoff coefficients for the Rational Method. Includes tables by land use, soil type, and slope, plus composite C calculations.
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