Do riparian buffer zones and new forest management practices reduce stream suspended sediment loads?: Re‐visiting the Afon Tanllwyth in Hafren Forest, Plynlimon, 20 years on
2021
Stott, Tim A.
Studies of forest clear‐felling operations in 1995–97 in the Afon Tanllwyth sub‐catchment of the upper River Severn on Plynlimon, mid‐Wales, by Stott et al. (Journal of Environmental Management (2001), 63, 3), indicated elevated suspended sediment loads (SSLs) immediately following timber harvesting. UK Forestry Commission (1993) Forests and Water Guidelines recommended that riparian buffer zones adjacent to streams were left unplanted. This study 20 years on assessed the SSLs at the same point in the Afon Tanllwyth for 21 months between January 2017 and September 2018. While SSLs reported by Stott et al. (Journal of Environmental Management (2001), 63, 3). increased during and after the clear‐felling operations, by 2017–18 (20 years later) they appear to have recovered to levels similar to those measured pre‐clear‐felling (1995), despite this study taking place only a few months after approximately 3 ha of mature forest was clear‐felled on the north side of the catchment. Although the mean monthly SSL for 2017–18 of 1628 ± 95 kg is slightly lower than the 1,800 ± 176 kg reported for 1995, the difference is not significant. When SSL is corrected for differences in total monthly flow the flow adjusted SSLs are 1,346 ± 132 kg for 1995 and 945 ± 55 kg for 2017–18, thus significantly lower in 2017–18. These new data for 2017–18 indicate that SSLs seem to have recovered to levels significantly below those measured and reported by Stott et al. (Journal of Environmental Management (2001), 63, 3–25) in 1995 pre‐clear‐felling period, likely as a result of the establishment of the 50 m buffer zone.
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