SHC 302 – Hydrology and Hydraulic Design: A Guide for Highway Drainage in Saudi Arabia

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Effective hydrology and hydraulic design are critical components of highway infrastructure, ensuring efficient water management, road durability, and flood mitigation. In Saudi Arabia, the Saudi Highway Code (SHC) 302 – Hydrology and Hydraulic Design outlines the essential guidelines for managing highway drainage, focusing on sustainable and robust solutions.

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This guide provides an in-depth overview of SHC 302, covering hydrologic considerations, drainage structures, and best practices for highway water management in Saudi Arabia’s diverse climatic conditions.

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Understanding Hydrology in Highway Design

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Hydrology in highway design revolves around estimating rainfall, runoff, and peak discharge rates to prevent water accumulation and potential roadway damage. Key hydrologic components include:

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1. Rainfall and Runoff Analysis

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• Rainfall Intensity-Duration-Frequency (IDF) Curves: Essential for determining peak rainfall events.

• Runoff Coefficients: Used to estimate the percentage of rainfall converted to runoff.

• Time of Concentration: The time taken for water to flow from the farthest point of a watershed to the drainage system.

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2. Hydrologic Procedure Selection

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The SHC 302 outlines different hydrologic methods for gauged and ungauged sites:

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• Regression Equations: Used for estimating peak discharge based on historical data.

• Rational Method: Suitable for small catchment areas to estimate peak runoff.

• Hydrograph Modeling: Simulates rainfall-runoff processes for large-scale planning.

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Hydraulic Design Considerations

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Highway hydraulic design involves ensuring that water flows efficiently through designated channels, culverts, and storm drainage systems. Key components include:

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1. Open Channels and Roadside Drains

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• Types of Open Drains: Natural streams, roadside ditches, and engineered channels.

• Flow Analysis: Includes steady and unsteady flow conditions, uniform and non-uniform flow types.

• Energy Considerations: Managing hydraulic jumps and preventing erosion through proper gradient design.

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2. Culverts and Bridges

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Culverts and bridges play a crucial role in allowing water to pass beneath roadways without causing structural damage.

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• Culvert Sizing: Based on flow rates and hydraulic efficiency.

• Inlet and Outlet Control: Ensuring smooth water entry and exit.

• Scour Protection: Preventing erosion around culvert and bridge foundations.

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3. Storm Drainage Systems

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SHC 302 emphasizes a structured approach to stormwater management through:

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• Gutter and Inlet Design: Proper spacing and capacity calculation to prevent road flooding.

• Hydraulic Grade Line (HGL) Calculation: Ensuring water flows at the designed capacity without overflow.

• Storage Facilities: Detention and retention basins to manage excess water.

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Best Practices for Highway Drainage in Saudi Arabia

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1. Adapting to Regional Hydrologic Conditions

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Saudi Arabia has varying hydrologic regions, requiring tailored approaches for flood management:

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• Arid Zones: Implementing water harvesting techniques.

• Urban Areas: Ensuring efficient stormwater drainage to prevent urban flooding.

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2. Implementing Climate-Resilient Designs

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With increasing climate variability, SHC 302 recommends:

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• Incorporating Green Infrastructure: Such as permeable pavements and bio-swales.

• Using Advanced Simulation Models: To predict extreme weather impacts.

• Ensuring Regular Maintenance: To keep drainage systems functional.

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Conclusion

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The SHC 302 – Hydrology and Hydraulic Design guide is a fundamental resource for engineers involved in highway planning and maintenance in Saudi Arabia. By implementing advanced hydrologic and hydraulic techniques, road networks can efficiently manage water flow, ensuring long-term sustainability and safety.

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