Commissioned by INVVU, the Hythe scheme required a thoughtful and collaborative approach to overcome both design constraints and environmental challenges on site. With complex ground conditions, varying pipe elevations, and limited space due to sloped terrain, the project demanded an innovative solution that traditional concrete structures alone could not provide. Through close coordination with the scheme designer and the use of modular construction methods, our team successfully delivered a durable, green-finish headwall system that met both functional and aesthetic requirements.
The Hythe project was brought to us by our client, INVVU, who required a solution for the installation of two headwalls. These headwalls were needed to allow water to be discharged from two separate pipes—a 1200mm pipe and a 150mm pipe—into a privately owned pond or lake.
The challenge
During the initial design phase, several challenges emerged due to the position and elevation of the two pipes. Both headwalls were to be constructed on a slope, and the outlets were at different levels.
The required width for each individual headwall meant that the two structures would have conflicted with one another. When these designs were tested against the existing ground levels, the models showed potential failure due to interfacing and ground instability. Additionally, incorporating two traditional concrete headwalls would have required a complex and bespoke solution that risked being costly and time-consuming.
Our solution
Our design team worked closely with the scheme designer to resolve the issues. We proposed a change in pipe alignment, slightly realigning them to bring their outlets closer together. This adjustment enabled us to design a single, larger modular winged headwall to accommodate both pipes, despite their staggered elevations.
Thanks to the modular nature of our bag system, we were able to combine the two outfalls into one structure—a solution that would not have been possible using concrete without extensive bespoke design.
The final headwall measured 2.1m in height and included wing walls to provide stability and structure. In addition, we incorporated gabion mattresses at the base of the headwall as a form of erosion protection, particularly given the high discharge expected from the 1200mm pipe.
Challenges and how we overcame them
After overlaying the original two-headwall design, we identified the exact locations of interference and clash. Using this information, we created a mock-up elevation to visualise a combined solution.
From there, we developed a detailed model of the single headwall that integrated both outfalls. The collaborative approach between our design team and the scheme designer allowed for a seamless transition from concept to execution, removing the need for complex and costly alternatives.
The installation itself presented another layer of difficulty. Taking place in the dead of winter, the work was carried out at one of the lowest points on site, where water inflow had to be managed daily. Despite the environmental conditions, the structure was installed safely and efficiently.
The result
The completed structure was delivered just in time for spring, allowing the pre-seeded bags to begin vegetating and establish a natural green finish in harmony with the surrounding landscape.
The final product is a robust, modular, and environmentally considerate solution that not only overcame the design and installation challenges but also delivered long-term resilience and aesthetic value. The Hythe project stands as a successful example of innovative, collaborative problem-solving and smart design execution.
Want to know more about Rootlok?
Rootlok is a cost-effective system that provides end users with a strong, yet flexible, green solution for retaining walls. It’s ability to vegetate creates a retaining wall that blends seamlessly with the natural environment. It is important to consider the choice of vegetation to ensure that the result is aligned with expectations and the ability to effectively and safely maintain it.