Geomorphic, discharge and substrate river restoration monitoring data from the Logie Burn, Scotland (2011 to 2014)

Restoration is applied to reinstate geomorphic processes and complexity in degraded streams, but case studies of responses remain rare. A 236 m long reach of the Logie Burn, a straightened sand-gravel bed stream in north-east Scotland was restored by reconnecting its pre-modification channel to improve habitat and reduce nutrient transfer. Morphological, sedimentary and retention (wood, phosphorous and organic matter) responses were monitored over 3 years. Monitoring over 2 years was also conducted in a nearby control reach. A net deposition response of 64.3 ± 32.1 m³, a near two-fold enlargement of channel cross section area and a reduction of bed slope from 0.0008 m m⁻¹ to 0.00014 m m⁻¹ were observed in the restored reach over 3 years. The control reach in contrast was relatively stable. After 3 years, relative pool volume and morphological complexity were similar to the control reach and its pre-restoration state. Substrate diversity (Shannon-Wiener index: H') after an initial increase, declined but at the end of the monitoring period was higher (H' = 1.26) than the control reach (H' = 1) and pre-restoration reach (H' = 0.8). Following restoration, the median sediment size (D50) of the majority of the restored main channel reduced from 3.4 mm to 1.5 mm – a similar value to pre-restoration (D50 = 1.6 mm) – reflecting the net deposition response although the overall grainsize distribution was not statistically different. No relationship between geomorphically effective flows and morphological change was found reflecting geomorphic sensitivity due to the reconnection work and wood recruitment mainly driven by tree collapse in response to channel readjustment. The retention of organic matter (OM) and total phosphorous (TP) did not increase in the main channel but did within the backwaters which also exhibited a statistically significant fining response. Overall, these results suggest that the physical habitat improvement value of the scheme so far has been limited but the creation of the backwaters may have increased the capacity of the reach to retain nutrients and fine sediment. This study was funded by the Rural and Environmental Science and Analytical Services (RESAS) division of the Scottish Government.