Lessons from practice: assessing early progress and success in river rehabilitation

Abstract

This article comprises a literature analysis of 41 river rehabilitation projects to assess the shortterm (5 years) ability of indicator groups to demonstrate progress towards river rehabilitation goals. Positive indications were compared to land-use, river size, rehabilitation intervention and time. A questionnaire was developed to investigate river manager's interpretation of rehabilitation success and to assess their level of adherence to recommendations in the literature with regard to rehabilitation assessment on a conceptual level. A total of 54 responses were received from respondents based in Germany, The Netherlands and the United Kingdom. The results indicate that macroinvertebrate indicators, while widely used in assessing river rehabilitation efforts, exhibited a lower frequency of positive responses than most other indicator types in the short term. Conversely, terrestrial floodplain indicators exhibited the most frequent level of positive response for all ecological type indicators leading to recommendations for further investigations into their use for short-term monitoring. Assessment procedures recommended in literature are largely followed, illustrating the advances that have been made with regard to assessment planning. Indicator responses are influenced by scale factors, for example, land-use and river size, that are often not considered by rehabilitation managers. While an emphasis is placed on ecological, hydrological and morphological indicators in monitoring schemes, the socioeconomic perspective (emphasized in the literature as forming an integral part of the river system) is neglected.

Improvement in physical river habitat quality in response to river restoration measures

“…In terms of the effect of restoration on the ecological status, the existence of riparian zones in good state appears to be important, as they reduce the input of nutrients and pesticides into the stream. The riparian zones with bands of 5-30 m width and longer than 1 km seem to provide the highest efficiency (Parson, Thoms 2007;Matthews et al 2010;Feld et al 2011). The creation of new longer meandering course with functional riparian zones a reduction of nutrients inflow should be achieved by proposed restoration.…”

Large woody debris “rewilding” rapidly restores biodiversity in riverine food webs

“…river habitat quality or the abundance of key taxa) as surrogates for effective ecosystem restoration remains unverified (Bernhardt & Palmer, 2011;Feld et al, 2011;Palmer et al, 2010). Where biomonitoring has been undertaken to assess restoration success, invertebrates or fish have often been the sole bioindicators used (Matthews, Reeze, Feld, & Hendriks, 2010;Whiteway, Biron, Zimmermann, Venter, & Grant, 2010; but see Kail et al, 2015). Despite being repeatedly advocated (Feld et al, 2011;Friberg et al, 2011;Pander & Geist, 2013), a more holistic, systembased view of restoration responses at higher levels of biological organisation is still lacking.…”

Characterizing a Major Urban Stream Restoration Project: Nine Mile Run (Pittsburgh, Pennsylvania, USA)

“…Post restoration, while the macroinvertebrate community seemed to be affected by large hydrologic events, improvements in community health persists despite these events (Figures a and f). The lagging recovery of stream macroinvertebrates is consistent with many stream restoration assessments (Matthews et al ., ) and may arise, at least in part, from the lack of upstream refugia in NMR due to stream burial (Figure ). In less impacted systems, upstream areas support important source populations allowing recolonization of downstream reaches (Gore, ).…”

“…While it seems to be growing increasingly clear that benthic macroinvertebrate communities recover relatively slowly, if at all, in urban systems (Blakely et al, 2006;Matthews et al, 2010;Meisenbach et al, 2012), this remains an indicator of choice in the literature. As noted previously, there are emerging efforts to evaluate biotic integrity across communities (Stranko et al, 2012); however, these often remain focused on instream communities and are similarly dismal in terms of recovery rates.…”