What are head walls?

Head walls refer to two distinct types of structures or formations: a steep geological slope at the head of a valley, and a built masonry or concrete wall used in civil engineering at the outlet of a drainpipe or culvert.

What Are Head Walls?

Head walls are structures or natural formations characterized by their position at the "head" or beginning of something, serving different purposes based on their context.

There are primarily two recognized definitions for head walls:

1. Geological Head Walls: The Valley Head Slope

In geology, a head wall refers to a steep slope forming the head of a valley.

• Description: This type of head wall is a natural geological feature, typically found at the uppermost end of a valley. It's often associated with mountainous or glaciated terrains.
• Formation: In glaciated valleys, these steep slopes often form the back wall of a cirque (a bowl-shaped depression carved by glacial erosion). As glaciers move, they scour out the valley floor and steepen the valley sides, including its head.
• Significance: Geological head walls are crucial landscape features that define the upper limits of many valleys, contributing to their unique geomorphology. They can be very challenging to traverse due to their steepness.

2. Engineering Head Walls: Drainage and Culvert Structures

In civil engineering and construction, a head wall is a wall of masonry or concrete built at the outlet of a drainpipe or culvert with the end of the conduit flush with the outer surface of the wall.

• Description: This type of head wall is a constructed barrier, typically made from durable materials like concrete or stone masonry. It is specifically designed to encase and support the end of a pipe or culvert (a tunnel carrying a stream or drain under a road or railway).
• Key Characteristics:
  • The pipe or culvert terminates flush with the outer face of the wall, meaning the end of the conduit is level with the wall's surface.
  • Can be built at both the inlet (where water enters) and outlet (where water exits) of a culvert, though the definition primarily highlights the outlet.
• Purpose and Benefits:
  • Erosion Control: Prevents erosion of the surrounding soil by dissipating the energy of discharged water and protecting the earth around the pipe from scour.
  • Structural Support: Provides essential support to the culvert or drainpipe, preventing it from shifting, collapsing, or being damaged by external forces (e.g., soil pressure, vehicle loads above).
  • Improved Hydraulics: Can help in directing water flow efficiently into or out of the culvert, reducing turbulence and potential blockages.
  • Protection: Shields the end of the conduit from debris, impacts, or undermining.
  • Aesthetics: Offers a neat and finished appearance to the culvert system, especially in visible locations.
  • Safety: By stabilizing the culvert and surrounding ground, it contributes to the overall safety of the infrastructure.

Head walls, whether natural or constructed, play critical roles in defining landscapes and ensuring the longevity and functionality of drainage infrastructure.