Revolutionizing Flood Management: The Subok Catchment Tunnel Feasibility Study
Nestled immediately to the northeast of Bandar Seri Begawan, the Subok catchment spans a striking 1,045 hectares. This unique catchment stretches approximately 2 kilometers wide and 7 kilometers long, bordered by the picturesque ridges of Bukit Selila, which rise up to 190 meters. The Sungai Subok, the main watercourse, flows southwest, feeding into the Sungai Kianggeh canal and eventually draining into the tidal Sungai Brunei. The strategic importance of this catchment has sparked an innovative study to explore the feasibility of a tunnel as a long-term solution to mitigate flooding, a persistent issue that has historically plagued the area.
Impacting various locations with alarming regularity. While earlier phases of flood mitigation schemes have notably reduced the frequency and severity of flooding, the problem persists, especially during heavy rains coinciding with high tides at the downstream end of the Kianggeh canal. The 1987 Sungai Subok/Sungai Kianggeh Flood Mitigation Study first introduced the concept of a diversion tunnel. This tunnel was envisioned as a solution to channel floodwaters away from built-up downstream areas, thereby protecting the city center of Bandar Seri Begawan from the devastating impacts of flooding.
The Tunnel Proposal
Few options of the tunnel routes were explored. The selected tunnel plan envisages a more ambitious 800-meter-long tunnel, descending to a maximum depth of approximately 60 meters below the ridge peak. The exit is strategically located near Simpang 723, Jalan Kota Batu, to drain into an existing stream and then into Sungai Brunei. This exit point is ideally positioned between Kampung Sungai Matan and Kampung Serdang, minimizing disruption while optimizing the tunnel’s flood diversion capabilities.
The proposed entrance area for the tunnel is generally flat and undeveloped, with potential access routes from Simpang 422, which is preferred as it would affect the least number of properties and require minimal land acquisition compared to the other routes.
Towards a Flood-Resilient Future
The Subok catchment tunnel project represents a forward-thinking approach to flood management. By diverting excess floodwaters away from vulnerable urban areas, this tunnel promises to enhance the resilience of Bandar Seri Begawan against flooding. The project balances engineering innovation with practical considerations to minimize community disruption and environmental impact.