city of austin drainage criteria manual

This manual provides comprehensive guidelines and standards for the design, construction, operation, and maintenance of drainage systems within the City of Austin, Texas. It aims to ensure the efficient and safe management of stormwater runoff, protect public health and safety, and preserve the environment. The manual is a valuable resource for engineers, developers, contractors, and other stakeholders involved in drainage projects within the city.

I. Introduction

This section provides an overview of the City of Austin Drainage Criteria Manual, outlining its purpose, scope, and the rationale behind its development. It also discusses the historical context of drainage management in Austin and highlights the key principles that underpin the manual’s content.

1.1 Purpose and Scope

The primary purpose of this manual is to establish clear and consistent standards for drainage design, construction, operation, and maintenance within the City of Austin. Its scope encompasses all aspects of stormwater management, including runoff collection, conveyance, treatment, and disposal. The manual aims to ensure the safe and efficient handling of stormwater while protecting public health, safety, and the environment.

1.2 Background and History

The City of Austin has a long history of addressing stormwater management challenges, evolving its approach as the city has grown and faced increasing urbanization. This manual reflects the city’s commitment to sustainable drainage practices, incorporating lessons learned from past experiences and embracing innovative solutions. The manual builds upon previous drainage guidelines and regulations, providing a comprehensive and updated framework for managing stormwater in Austin.

1.3 Organization and Structure

This manual is organized into seven sections, each covering a specific aspect of drainage design and management. Each section is further divided into subsections that provide detailed information and guidance; The manual follows a logical flow, starting with introductory concepts and progressing to specific design principles, infrastructure, management practices, and best management practices. Appendices at the end of the manual provide supplementary materials, including tables, charts, software resources, references, and a glossary of terms.

II. Definitions and Terminology

This section defines key terms, concepts, and standards related to drainage design and management within the City of Austin. A clear understanding of these definitions is crucial for consistent application of the manual’s guidelines and for effective communication among stakeholders involved in drainage projects. The definitions provided here are consistent with industry standards and practices, ensuring a common understanding of technical terms and concepts.

2.1 Key Terms

This section defines key terms related to drainage design and management, ensuring a common understanding of terminology used throughout the manual. It includes definitions for concepts such as stormwater runoff, drainage basin, detention pond, infiltration, and other relevant terms. These definitions provide a foundation for understanding the technical principles and practices outlined in the manual.

2.2 Drainage Design Standards

This section outlines specific standards and guidelines for the design of drainage systems in the City of Austin. It addresses aspects such as pipe sizing, slope calculations, channel dimensions, and other technical specifications. These standards ensure that all drainage projects meet minimum requirements for functionality, safety, and environmental protection.

2.3 Regulatory Framework

This section provides an overview of the relevant laws, ordinances, and regulations governing drainage activities within the City of Austin. It includes information about permits, inspections, enforcement mechanisms, and other legal aspects related to drainage design and construction.

III. Drainage Design Principles

This section outlines the fundamental principles and methodologies used in the design of drainage systems. It covers key aspects such as rainfall analysis, runoff estimation, hydraulic analysis, channel design, and detention and retention techniques, all essential for effective stormwater management.

3.1 Rainfall Analysis

Accurate rainfall analysis is crucial for determining the design storm events that drainage systems must accommodate. This involves analyzing historical rainfall data, identifying rainfall frequency and intensity, and developing rainfall-depth-duration curves. The manual outlines the specific methods and data sources used for rainfall analysis in the City of Austin.

3.2 Runoff Estimation

Once rainfall characteristics are established, runoff estimation methods are employed to determine the volume and rate of stormwater runoff generated from various land uses and impervious surfaces. This section details the approved runoff estimation methods, including the Rational Method, the SCS Curve Number Method, and the TR-55 Method. The manual also provides guidance on selecting the appropriate method based on site conditions and project scope.

3.3 Hydraulic Analysis

Hydraulic analysis is essential to assess the flow capacity of drainage channels, pipes, and other conveyance systems. This section outlines the principles and methods used to perform hydraulic analysis, including the use of hydraulic software, Manning’s equation, and other appropriate techniques. The manual provides guidance on determining flow velocities, water depths, and energy gradients to ensure safe and efficient stormwater conveyance.

3.4 Channel Design

This section focuses on the design of drainage channels, including open channels, culverts, and storm sewers. It covers topics such as channel geometry, hydraulic capacity, erosion control, and environmental considerations. The manual provides guidance on selecting appropriate channel materials, sizing, and layout to ensure proper drainage and minimize environmental impacts.

3.5 Detention and Retention

This section discusses the design and implementation of detention and retention ponds, which are essential components of stormwater management systems. The manual outlines the principles of detention and retention, including the calculation of storage volumes, outflow rates, and water quality considerations. It also provides guidance on the selection of appropriate pond types, design features, and maintenance practices.

IV. Drainage Infrastructure

This section details the various types of drainage infrastructure commonly used in the City of Austin, including storm sewer systems, drainage channels, detention ponds, and infiltration practices. It covers design considerations, construction techniques, and maintenance requirements for each infrastructure component, ensuring efficient and sustainable stormwater management.

4.1 Storm Sewer Systems

Storm sewer systems are a primary component of the City of Austin’s drainage infrastructure, designed to collect and convey stormwater runoff from streets, parking lots, and other impervious surfaces. This section outlines the design principles, construction standards, and maintenance procedures for storm sewer systems, ensuring their efficient operation and long-term reliability.

4.2 Drainage Channels

Drainage channels are open conveyances designed to transport stormwater runoff across the city’s landscape. This section delves into the design considerations, construction specifications, and maintenance practices for drainage channels, ensuring their effectiveness in managing stormwater flow while preserving natural aesthetics and ecological values.

4.3 Detention Ponds

Detention ponds are engineered structures designed to temporarily store stormwater runoff, reducing peak flow rates and mitigating downstream flooding. This section outlines the design criteria, construction requirements, and operational considerations for detention ponds within the City of Austin, emphasizing their role in managing stormwater runoff and enhancing water quality.

4.4 Infiltration Practices

Infiltration practices are designed to promote the absorption of stormwater runoff into the ground, mimicking natural processes and reducing runoff volume. This section explores various infiltration techniques, including bioretention areas, rain gardens, and permeable pavements, highlighting their benefits in managing stormwater and improving water quality.

V. Drainage Management

This section focuses on the various aspects of managing drainage systems within the City of Austin, encompassing permitting procedures, maintenance protocols, monitoring strategies, and regulatory frameworks. It outlines the responsibilities of different stakeholders, including the City, developers, and property owners, in ensuring the efficient and sustainable operation of drainage infrastructure.

5.1 Drainage Permitting

The City of Austin requires permits for various drainage-related activities, including new development, redevelopment, and infrastructure modifications. This section outlines the permitting process, including application requirements, review criteria, and approval procedures. It also clarifies the responsibilities of applicants and the City in ensuring compliance with drainage regulations and standards.

5.2 Drainage Maintenance

This section addresses the critical role of maintenance in ensuring the long-term functionality and effectiveness of drainage systems. It outlines the responsibilities of property owners, developers, and the City in maintaining drainage infrastructure, including storm sewers, channels, detention ponds, and other components. It also provides guidance on inspection schedules, cleaning procedures, and repair protocols to prevent system failures and minimize the impact of stormwater runoff.

5.3 Drainage Monitoring

This section focuses on the importance of ongoing monitoring to assess the performance and effectiveness of drainage systems. It outlines methods for collecting data on rainfall events, runoff volumes, water quality, and system capacity. The manual describes the use of sensors, gauges, and other monitoring tools to track system performance and identify potential issues. It also emphasizes the importance of data analysis and reporting to inform maintenance decisions and improve the overall efficiency of the city’s drainage infrastructure.

5.4 Drainage Regulations

This section provides a detailed overview of the City of Austin’s drainage regulations, including ordinances, codes, and permitting requirements. It clarifies the responsibilities of property owners, developers, and contractors in managing stormwater runoff and maintaining drainage systems. The manual also explains the enforcement procedures for violations of drainage regulations and the potential consequences for non-compliance.

VI; Best Management Practices (BMPs)

This section highlights the importance of implementing Best Management Practices (BMPs) for stormwater management. BMPs are a range of techniques and strategies that aim to minimize the negative impacts of stormwater runoff on the environment and public infrastructure. The manual outlines various BMPs, including green infrastructure, low-impact development (LID) techniques, and water quality protection measures. It emphasizes the benefits of adopting BMPs for achieving sustainable drainage systems and promoting a healthy urban environment.

6.1 Green Infrastructure

Green infrastructure refers to the use of natural systems and technologies to manage stormwater runoff. This section provides guidance on implementing green infrastructure solutions in Austin, such as rain gardens, bioswales, green roofs, and permeable pavements. These solutions are designed to mimic natural processes and provide multiple benefits, including reducing runoff volumes, improving water quality, enhancing aesthetics, and creating habitat for wildlife.

6.2 Low Impact Development (LID)

Low Impact Development (LID) is a site design approach that minimizes the impact of development on stormwater runoff. This section outlines LID principles and techniques for managing runoff at the source, emphasizing the use of natural processes and features to infiltrate, filter, and detain stormwater. LID practices help reduce flooding, improve water quality, and create more sustainable and resilient urban environments.

6.3 Water Quality Protection

This section addresses the importance of protecting water quality within the City of Austin’s drainage system. It highlights the potential impacts of stormwater runoff on water bodies and outlines best management practices (BMPs) to minimize pollution. The manual emphasizes the need for proper design and maintenance of drainage infrastructure to prevent the discharge of pollutants, such as sediment, nutrients, and hazardous materials, into local waterways.

VII. Appendices

The Appendices provide supplementary information and resources to support the content presented in the main body of the manual. This includes technical details, design tools, and reference materials that can be used for specific applications. The Appendices serve as a valuable resource for practitioners seeking detailed information and guidance on specific aspects of drainage design and management.

7.1 Design Tables and Charts

This section provides a collection of design tables and charts that are essential for drainage calculations and estimations. These tables and charts contain data on rainfall intensities, runoff coefficients, hydraulic properties of channels, detention pond sizing, and other relevant parameters. They serve as quick references for engineers and designers during the drainage design process.

7.2 Drainage Software

This appendix lists and briefly describes drainage software programs that are commonly used in the design and analysis of drainage systems. These programs are designed to streamline the process of hydraulic modeling, runoff estimation, detention pond sizing, and other drainage-related calculations. The manual may also provide recommendations on specific software programs that meet the City of Austin’s requirements.

7.3 References

This appendix provides a list of relevant references, including technical reports, research articles, industry standards, and other publications that have been used in the development of this drainage criteria manual. These references provide further information on the technical principles, design methodologies, and best practices that underpin the manual’s guidelines.

7.4 Glossary

This glossary defines key terms and technical jargon used throughout the drainage criteria manual. It provides a comprehensive reference for understanding the terminology and concepts related to drainage design, management, and best practices.