Drainage 101: Keeping Forestry Roads and Catchments on Track

Forestry South Africa’s (FSA) Environmental Management Committee (EMC) hosted its latest webinar on ‘Managing Water Flow and Drainage within Forestry Landholdings’, bringing together forestry road specialists, environmental managers and leading researchers to unpack why drainage management is critical to maintain good road networks, and to prevent erosion from commercial compartments, and sedimentation of conservation areas.

Drainage: Reasons and Effects of Poor Installations

Geoff Hurd, a Forestry Road Specialist at CMO, opened proceedings with a somber reminder that “forestry roads are under more scrutiny than ever, as poor drainage drives sedimentation, erosion and lost access”. Throughout Session One, Geoff took attendees through the three non-negotiables of good drainage design: keeping the road out of the water, keeping the water out of the road, and getting water away from the road. Beyond imparting his wisdom, he provided the webinar participants with a practical toolbox of tips and techniques when it comes to camber, side drains, mitre drains, culverts and stream crossings.

What made Geoff’s talk so refreshing was his bluntness about failure points, be it blocked culverts, collapsing banks or poor maintenance. He also reinforced the message that the outlets, wherever water finally leaves a drain, are consistently the most vulnerable part of any system, for the erosion risk of both drainage structures and soil resources in commercial compartments. The highest risk is in the first year after construction, during periods of high rainfall, and when there is harvesting and transport traffic. So when the three coincide, be prepared for the perfect storm.

Geoff’s presentation is a must for anyone involved with forestry roads, with his final words becoming the mantra for many who joined the webinar, “no road is better than its drainage”.

Watch Geoff’s presentation in full: EMC Drainage Webinar – Geoff Herd – Drainage: Reasons and Effects of Poor Drainage

Lessons From the Field: Applied Research and Case Studies

Professor Bruce Talbot and MSc student Philisiwe Sithole of Stellenbosch University’s Forest Operations group followed Geoff, presenting their research on ‘Managing Waterflow and Drainage within Forestry Landscapes’. Funded through the Forestry Sector Innovation Fund, Bruce’s project that looks at micro-catchment approach to understanding, quantifying and monitoring soil loss. Using a network of sediment traps and erosion pins, as well as unmanned LiDAR surveys and RUSLE-based modelling, the team is building a clearer, more cost-effective picture of where sediment comes from and how confidently we can measure it. It is a timely reminder that good drainage starts with good soil science.

To watch Bruce and Philisiwe’s presentation in full: EMC Drainage Webinar: Bruce Talbot and Philisiwe Sithole – Why Soil Science is so Vital

Mondi’s Dr Brent Corcoran and Sifiso Kunene rounded off the session by zooming back out to the landscape scale. Brent’s framing was simple but pointed, demonstrating that erosion and sedimentation sit at the top of the operational risk register, and that it’s not only a roads problem. Compartments, as well as roads, intercept and concentrate the natural waterflow pathways.  For example, where a harvesting extraction route sits directly beneath a road culvert outlet, the result is a sharp spike in volume and velocity and much higher risk of erosion.

Brent linked this back to Bruce’s soil loss equation, warning that with climate change delivering fewer, more intense rainfall events, soil cover is the one variable land managers must control to avoid both gradual soil loss over time, and serious erosion and sedimentation events. Brent noted best practice requirements for the Forestry Sector, including phasing harvest block sizes to manage slope length and peak runoff, clear contractor standards for roads and stream crossings, and root-cause investigation on every erosion incident to feed back into a continuous improvement cycle.

Sifiso Kunene then brought the discussion down to implementation, introducing Mondi’s long-standing road optimisation programme aimed at reducing road density and realigning roads away from steep slopes, as well as sensitive areas and other problem areas. Engineering design (alignment, slope and culvert spacing) is checked against flow models in consultation with specialists including how their network interacts with public road drainage. Maintenance has shifted from a time-based to a productivity-based approach, helping stretch limited budgets further. Annual refresher training for foresters, road contractors and the environmental team is integral to ensuring alignment on standards, as “one blocked culvert puts pressure on every structure downstream”.

 Both Brent and Sifiso closed with the same underlying message, roads and stream crossings matter, but they’re only one part of an integrated catchment-level approach that must weigh roads management, harvesting activities, residue management and weed control against each other, not in isolation.

To watch Brent and Sifiso’s presentation click here: EMC Drainage Webinar – Brent Corcoran and Sifiso Kunene

Moving forward

Taken together, the three sessions offer far more than a single afternoon’s viewing, they amount to a genuinely practical masterclass in drainage management, from the fundamentals of a well-placed mitre drain right through to catchment-level decision-making. With each presentation now available to watch in full on FSA’s website, the webinar is a training resource providing invaluable practical advice for foresters and road contractors brushing up on the basics, and equally useful for students and early-career practitioners building their understanding of how water, soil and timber production all interact on the ground. In an industry where, as Geoff Hurd put it, “no road is better than its drainage”, having this expertise just a click away is a resource well worth returning to.

“It has only been a couple of weeks since the Drainage Webinar and already I have seen its advice in action in Merensky’s plantation. One of our Plantation Managers quoted Geoff’s ‘drainage, drainage, drainage’ when assessing a small erosion scar, taking me to address the drainage at the head of the scar as Geoff suggested, which I found really encouraging. Then, in another plantation I saw a TLB in action which was very useful for creating side drains, something the foresters there had always thought was a no-go ahead of the webinar. It’s really good to see the positive uptake of the advice and practical applications imparted during these EMC seminars.” – Hamish Whyle, Technical Services and Environmental Manager, Merensky Timbers

 The next EMC webinars will be a series on biodiversity, more information to come shortly.

Source: Forestry in Focus

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