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Storm Sewer in Tx: Pt 3-The Significance of HGL (Hydraulic Grade Line)

HGL (Hydraulic Grade Line)


Welcome to Part 3 of our comprehensive series on storm sewer systems in Texas. In this segment, we will explore a critical aspect of storm sewer design: the Hydraulic Grade Line (HGL). Understanding the HGL is essential for optimizing stormwater management in the Lone Star State.

Section 1: Understanding the Hydraulic Grade Line

The Role of HGL in Storm Sewers

The Hydraulic Grade Line (HGL) is a vital concept in storm sewer design, representing the total energy of water flow within the system.

Energy Components

Understand the components of HGL, including the elevation head, pressure head, and velocity head, and how they relate to storm sewer performance.

Balancing Act

Balancing the energy components of HGL is crucial to ensure efficient and effective stormwater conveyance.

Section 2: Designing for HGL Efficiency

Optimizing Storm Sewer Design

Designing storm sewer systems that consider HGL efficiency leads to improved performance and cost-effectiveness.

Pipe Sizing

Proper pipe sizing is critical to maintain the desired HGL gradient and prevent issues such as flooding or backflow.

Inlets and Outlets

Select and design inlets and outlets that minimize energy losses and facilitate efficient stormwater flow.

Slope and Gradients

Achieving the right slope and gradients in storm sewer systems ensures that HGL is maintained within acceptable limits.

Section 3: HGL in Extreme Conditions

Addressing Extreme Weather

Incorporating HGL considerations in storm sewer design becomes even more critical during extreme weather events.

Capacity for Extreme Flow

Storm sewer systems must be capable of accommodating extreme flow rates while maintaining HGL stability.

Flood Prevention

Proper HGL management helps prevent flooding during heavy rainfall and other extreme weather conditions.

Section 4: Maintenance and Monitoring

Continuous Evaluation

Regular maintenance and monitoring are essential to keep storm sewer systems operating within desired HGL parameters.

Cleaning and Inspections

Cleaning and inspecting storm sewer components help identify and rectify issues that may disrupt HGL.

Data Collection

Collecting data on stormwater flow and HGL trends aids in proactive maintenance and system improvements.


Understanding the significance of the Hydraulic Grade Line (HGL) is paramount for efficient storm sewer design and operation in Texas. Balancing energy components, optimizing design, addressing extreme conditions, and implementing effective maintenance and monitoring practices are crucial for successful stormwater management. In Part 4 of our series, we will explore the "Importance of outfall elevation into a channel" in storm sewer systems. JRH Engineering & Engineering Services, Inc. remains committed to providing you with the knowledge and expertise needed to excel in stormwater management projects across the Lone Star State.

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