Spillways

Definition

Spillways are structures built to allow excess water to flow over or around a dam, preventing overflow and ensuring the safety and stability of the dam and its reservoir. They serve a critical function in managing water levels during heavy rainfall or snowmelt, directing surplus water away from the dam to protect it from potential damage and downstream flooding.

5 Must Know Facts For Your Next Test

1. Spillways can be classified into different types, including overflow spillways, side-channel spillways, and gated spillways, each designed for specific operational needs.
2. The design of a spillway must account for the maximum probable flood (MPF) events to ensure that it can handle extreme weather conditions without failure.
3. Spillways often incorporate energy dissipation features, such as stilling basins or riprap, to reduce the velocity of the water and prevent erosion downstream.
4. A well-designed spillway not only protects the dam but also plays an essential role in maintaining environmental flow requirements downstream.
5. The maintenance of spillways is crucial to their effectiveness; blockages or structural issues can significantly compromise their ability to manage overflow.

Review Questions

• How do spillways contribute to the overall safety and functionality of dams?
  • Spillways are essential for managing excess water in reservoirs created by dams. They allow for controlled release during heavy rainfall or rapid snowmelt, which helps prevent overflow that could lead to dam failure. By directing surplus water safely away from the dam, spillways help maintain structural integrity and protect surrounding areas from potential flooding.
• Compare and contrast different types of spillways and their specific applications.
  • Different types of spillways serve varied purposes based on the design requirements and site conditions. Overflow spillways typically allow water to flow over the top of a dam, which is suitable for low-crest structures. In contrast, gated spillways can control flow rates using adjustable gates, making them ideal for managing fluctuating water levels. Side-channel spillways direct water around the dam rather than over it, minimizing erosion risk and providing safer downstream conditions.
• Evaluate the impact of hydraulic jumps at spillways on downstream environments and engineering designs.
  • Hydraulic jumps occurring at spillways can significantly affect downstream environments by altering flow characteristics and sediment transport. When water transitions from supercritical to subcritical flow at a spillway, it can create turbulence and energy dissipation. This has implications for engineering designs, as engineers must incorporate features that manage these energy changes to prevent erosion and ensure ecological stability downstream. Understanding these interactions is critical for sustainable dam management.

Related terms

Hydraulic Jump: A sudden change in flow conditions of a fluid, characterized by a transition from supercritical flow to subcritical flow, often resulting in a rise in water surface elevation.

Reservoir: An artificial lake or storage area created by damming a river or stream to hold water for various uses, including water supply, hydroelectric power generation, and flood control.

Weir: A barrier across a river designed to alter its flow characteristics, allowing for measurement of discharge and control of water levels.