Sizing efficient underdrains for treatment wetlands

Area of Science:

• Environmental Engineering
• Water Resource Management
• Hydrology

Background:

• Treatment wetlands are crucial for mitigating urban runoff impacts.
• Lack of consensus exists on design guidelines, with underdrain system effects understudied.

Purpose of the Study:

• To develop and apply an analog model for evaluating underdrain system performance in treatment wetlands.
• To assess the spatial heterogeneity of flow entering underdrain networks.
• To provide insights for optimizing treatment wetland design.

Main Methods:

• Development of a simple analog model to simulate saturated underdrain network behavior.
• Application of the model to a treatment wetland in the Paris area.
• Evaluation of flow distribution and identification of design parameters like the rugosity coefficient.

Main Results:

• The analog model indicated the underdrain network was undersized.
• An undersized network likely resulted in uneven infiltrating flow distribution.
• The model proved useful for optimization and highlighted the importance of conservative rugosity coefficient values.

Conclusions:

• Underdrain system design is critical for uniform flow distribution in treatment wetlands.
• The analog model serves as a valuable tool for optimizing underdrain network design.
• Conservative rugosity coefficient selection is recommended for effective underdrain system design.