The City of Austin Drainage Criteria Manual establishes standard principles and practices for designing and constructing drainage systems within Austin, Texas, and its extraterritorial jurisdiction. This document covers topics such as stormwater management, floodplain regulations, and drainage design standards. The manual provides design specifications for various developments.
Purpose and Scope of the Manual
The primary purpose of the City of Austin Drainage Criteria Manual is to establish standardized principles and practices for the design and construction of drainage systems. This includes stormwater quantity, collection, storage, conveyance, and disposal within the City of Austin and its extraterritorial jurisdiction. The manual aims to ensure that all drainage infrastructure is planned and designed in accordance with city policy.
The scope of the manual encompasses various aspects of drainage design and management. It provides detailed design factors, formulas, graphs, and procedures for addressing stormwater runoff. The manual addresses topics such as street flow, inlets, storm drains, open channels, culverts, and stormwater management facilities. It also includes regulations and standards related to floodplain management and drainage charge administration. The manual intends to protect and restore watersheds, protect the Citys investment in stream restoration and natural channel design projects, and provide guidance for erosion and sedimentation control measures.
The Drainage Criteria Manual serves as a crucial reference for developers, engineers, and city staff involved in land development and construction projects within Austin. It is designed to interpret and specify the Land Development Code for drainage in the City of Austin. The manual is regularly updated and amended to reflect the latest industry standards and regulatory requirements.
Applicability and Jurisdiction
The City of Austin Drainage Criteria Manual has broad applicability to all development, construction, and land management activities within the City of Austin, Texas, and its extraterritorial jurisdiction (ETJ). This means that any project involving alterations to land that may affect stormwater runoff, drainage patterns, or floodplains must adhere to the standards and guidelines outlined in the manual.
The manual’s requirements extend to both public and private projects, including residential, commercial, industrial, and infrastructure developments. Specific areas of focus include site development, subdivision planning, building construction, and the installation or modification of drainage facilities. The provisions also apply to projects undertaken by City departments, agencies, or contractors.
Regarding jurisdiction, the City of Austin’s drainage policy governs the planning and design of drainage infrastructure not only within the city limits but also in areas subject to its ETJ. This ensures a consistent approach to stormwater management and flood control across a broader geographical area. The ETJ typically extends several miles beyond the city limits, depending on the type of regulation. It is important to verify the exact boundaries of the ETJ as it may change over time.
The manual is one of the Technical Criteria Manuals, which interpret and specify the Land Development Code for drainage in Austin.
Key Definitions and Terminology
Understanding the key definitions and terminology presented within the City of Austin Drainage Criteria Manual is crucial for accurate interpretation and application of its standards. Several terms have specific meanings within the context of drainage design and stormwater management. These definitions clarify the intent of the manual and ensure consistency in its implementation.
Key terms include “stormwater runoff,” which refers to the surface water flow generated by rainfall events. “Drainage system” encompasses the network of natural and man-made features that convey stormwater, including channels, pipes, and detention ponds. “Floodplain” designates areas susceptible to inundation during specified flood events.
“Hydrologic modeling” involves simulating the rainfall-runoff process to predict stormwater flows. “Hydraulic modeling” focuses on analyzing the flow of water within drainage systems. “Erosion and sedimentation control” refers to measures taken to minimize soil loss and prevent sediment pollution. “Best Management Practices (BMPs)” are structural or non-structural techniques used to manage stormwater runoff and reduce pollution.
Familiarity with these and other defined terms is essential for engineers, developers, and city staff involved in drainage-related projects. The manual provides a comprehensive glossary to ensure consistent understanding and application of its criteria. Precise interpretation of these terms is paramount for compliance with the manual’s requirements and effective management of stormwater within the City of Austin and its extraterritorial jurisdiction.
Stormwater Runoff Management Standards
The City of Austin Drainage Criteria Manual establishes stringent stormwater runoff management standards to mitigate the impacts of development on water quality and quantity. These standards aim to protect the city’s watersheds and infrastructure from the adverse effects of increased runoff. Compliance with these standards is mandatory for all new development and redevelopment projects within Austin and its extraterritorial jurisdiction.
Key requirements include controlling peak flow rates to pre-development levels for specified storm events. This ensures that downstream areas are not subjected to increased flooding. Volume reduction strategies, such as infiltration and rainwater harvesting, are encouraged to minimize the amount of runoff discharged into waterways. Water quality treatment measures, such as constructed wetlands and biofiltration, are required to remove pollutants from stormwater before it is released.
The manual specifies design criteria for various stormwater control measures (SCMs), including detention ponds, retention ponds, and green infrastructure. These SCMs must be designed to meet specific performance standards for pollutant removal and flow control. The manual also addresses erosion and sedimentation control, requiring developers to implement measures to prevent soil loss during construction activities.
Effective stormwater runoff management is crucial for protecting Austin’s water resources and maintaining the integrity of its drainage infrastructure. The standards outlined in the Drainage Criteria Manual provide a framework for achieving these goals.
Drainage System Design Principles
The City of Austin Drainage Criteria Manual emphasizes several key drainage system design principles to ensure effective and sustainable stormwater management. These principles guide engineers and developers in creating drainage systems that protect property, infrastructure, and the environment. A primary principle is minimizing impervious cover to reduce runoff volume and promote infiltration. Site designs should incorporate green infrastructure elements, such as permeable pavements and vegetated swales, to mimic natural hydrologic processes.
Another crucial principle is conveying stormwater safely and efficiently. Drainage systems must be designed to handle peak flows from design storm events without causing flooding or erosion. Proper sizing of pipes, channels, and culverts is essential to achieve this goal. Additionally, the manual promotes a hierarchical approach to drainage design, starting with on-site controls and progressing to regional facilities.
Erosion and sedimentation control are integral to drainage system design. Measures must be implemented to prevent soil loss during construction and to stabilize drainage channels. The manual also emphasizes the importance of maintenance and accessibility. Drainage systems should be designed to allow for easy inspection and maintenance to ensure their long-term functionality.
Sustainable and resilient drainage systems are achieved by adhering to these design principles, which protect Austin’s water resources.
Hydrologic and Hydraulic Modeling Requirements
The City of Austin Drainage Criteria Manual establishes specific hydrologic and hydraulic modeling requirements to ensure accurate assessment and management of stormwater runoff. These requirements dictate the methodologies and parameters used to simulate rainfall-runoff processes and flow characteristics within drainage systems. Accurate modeling is crucial for designing effective stormwater infrastructure and mitigating flood risks.
The manual specifies approved hydrologic models for estimating runoff rates and volumes, such as the Rational Method and hydrologic models like HEC-HMS. Model selection depends on the size and complexity of the drainage area. Specific rainfall data, including intensity-duration-frequency curves, must be used in hydrologic modeling to reflect local climatic conditions. Detailed guidance is provided on determining appropriate model parameters, such as curve numbers and time of concentration.
Hydraulic modeling is required to analyze flow conveyance through drainage structures, including pipes, channels, and culverts. The manual specifies acceptable hydraulic models, such as HEC-RAS, for simulating water surface profiles and assessing hydraulic capacity. Modeling must consider factors such as channel geometry, roughness coefficients, and backwater effects. Detailed guidelines are provided on model calibration and validation to ensure accuracy and reliability.
These rigorous modeling requirements ensure that drainage systems are designed based on sound engineering principles.
Erosion and Sedimentation Control Measures
The City of Austin Drainage Criteria Manual places significant emphasis on erosion and sedimentation control measures to minimize soil loss and protect water quality during construction and development activities. These measures are essential for preventing sediment from entering waterways, which can degrade aquatic habitats and impair water resources. The manual outlines specific requirements for implementing effective erosion and sediment control practices on construction sites.
The manual requires the development and implementation of an Erosion and Sediment Control Plan for all construction projects. This plan must identify potential erosion hazards and specify the control measures to be employed. Approved control measures include silt fences, erosion control blankets, temporary vegetation, and sediment traps. The manual provides detailed specifications for the design, installation, and maintenance of these measures.
Regular inspections of erosion and sediment control measures are required to ensure their effectiveness. The manual outlines inspection procedures and reporting requirements. Corrective actions must be taken promptly to address any deficiencies or failures of control measures. The manual also addresses long-term erosion control measures, such as permanent vegetation and structural stabilization, to ensure site stability after construction is completed.
Adherence to these stringent erosion and sedimentation control requirements is crucial for protecting the environment and maintaining water quality in Austin.
Floodplain Management Regulations
The City of Austin Drainage Criteria Manual includes comprehensive floodplain management regulations designed to minimize flood risks and protect life and property within the city. These regulations are essential for ensuring that development activities do not exacerbate flooding problems and comply with federal requirements.
The manual establishes detailed procedures for determining floodplain boundaries and delineating flood hazard zones. These procedures are based on hydrologic and hydraulic modeling, using rainfall data and topographic information. The manual specifies design standards for development within floodplains, including requirements for elevation, floodproofing, and stormwater detention.
The regulations restrict certain types of development within floodplains to minimize potential flood damage. The manual outlines specific criteria for obtaining permits for construction activities in flood hazard zones. These criteria address issues such as building elevation, structural integrity, and the impact on flood storage capacity. The manual also requires developers to provide compensatory storage for any floodplain areas that are filled or altered.
Regular updates to the floodplain maps and regulations are necessary to reflect changing conditions and improve flood risk management. Adherence to these regulations is crucial for protecting the community from the devastating impacts of flooding.
Drainage Charge Administration
The City of Austin Drainage Criteria Manual outlines the procedures for drainage charge administration, which involves assessing fees to property owners to fund the construction and maintenance of stormwater infrastructure. These charges ensure that new developments contribute to the overall drainage system and mitigate their impact on stormwater runoff.
The manual specifies the method for calculating drainage charges, taking into account factors such as impervious cover, land use, and location within the city. The fees collected are used to finance projects that improve drainage capacity, reduce flooding, and enhance water quality.
The drainage charge administration process includes provisions for exemptions and credits, such as for properties that implement on-site stormwater management practices. The manual also establishes procedures for appealing drainage charge assessments.
The city is responsible for managing the drainage charge fund and ensuring that it is used effectively to address drainage needs throughout the community. Regular audits and reports are conducted to maintain transparency and accountability in the administration of drainage charges. The Drainage Criteria Manual provides the technical and administrative framework for effective stormwater management.
Maintenance and Inspection Requirements
The City of Austin Drainage Criteria Manual details comprehensive maintenance and inspection requirements for all stormwater control measures (SCMs) to ensure their continued effectiveness. These requirements are crucial for preventing system failures, maintaining water quality, and protecting against flooding.
The manual specifies the frequency and scope of inspections, which vary based on the type and size of the SCM. Regular inspections are conducted by city personnel or qualified professionals to identify any deficiencies, such as sediment buildup, vegetation overgrowth, or structural damage.
Property owners are responsible for maintaining SCMs on their land in accordance with the manual’s guidelines. Maintenance activities may include removing debris, repairing erosion, and ensuring proper vegetation management. The manual provides detailed instructions on how to perform these tasks effectively.
The city enforces compliance with the maintenance and inspection requirements through regular audits and site visits. Failure to properly maintain SCMs can result in enforcement actions, including fines and corrective orders. The Drainage Criteria Manual ensures long-term functionality and performance of drainage systems.
Updates and Amendments to the Manual
The City of Austin Drainage Criteria Manual is a living document, subject to periodic updates and amendments to reflect changes in regulations, best management practices, and technological advancements. These revisions ensure the manual remains current and effective in addressing evolving stormwater management challenges.
The process for updating and amending the manual involves input from various stakeholders, including city staff, developers, engineers, and environmental groups. Proposed changes are carefully reviewed and evaluated to determine their potential impact on drainage design and water quality.
Public input is an important part of the revision process. The city provides opportunities for public comment on proposed updates and amendments, allowing stakeholders to voice their concerns and suggestions. This collaborative approach ensures that the manual reflects the needs and priorities of the community.
Once approved, updates and amendments are incorporated into the manual and made available to the public. The city provides training and guidance to help users understand and implement the revised requirements. This commitment to continuous improvement ensures effective drainage management.