Application of ecological and aesthetic parameters for riparian quality assessment of a small tropical river in eastern India

摘要

Assessments of the ecological quality of riparian zones help ascertain the status of channel-floodplain linkages, which are often affected by anthropogenic interventions, resulting in stream health degradation. Here we have evaluated the riparian condition of 54 sites along the River Dulung in eastern India using various ecological and aesthetics related indices for demarcating degraded channel reaches. Among the ecological parameters, the Qualitat del Bosc de Ribera (QBR) Index considers key aspects of vegetation, such as coverage and structure, as well as morphological aspects and anthropogenic interference in the landscape. The Riparian Strip Quality Index (RSQI) evaluates the ecological condition of riparian habitats based on the percentage of riparian vegetation, as was delineated from high resolution satellite images. The vegetation robustness was assessed using the Normalized Difference Vegetation Index (NDVI). The RSQI and NDVI parameters were extracted for a series of concentric buffers of varying widths on either side of the channel to differentiate between the vegetation cover on either bank and their changes with increasing distance from the channel. Since effective ecological restoration requires active public involvement, a perception survey was conducted for exploring links between the ecolo-gical quality and aesthetic appeal of the studied sites. Results suggest that majority of the sites have fair eco-logical quality, with a median QBR value of 60. The riparian strip quality is lower, with an average RSQI score of 55. This discrepancy may result from the qualitative (QBR) versus quantitative (RSQI) nature of the two indices employed. Nevertheless, both indices indicate that all sites are disturbed to some degree, mainly due to an-thropogenic activities like ambient agriculture and natural processes like recurrent monsoonal floods and riv-erbank erosion. Results of the perception survey indicate that sites with higher ecological quality garner more public appeal, with attributes like the state of the surrounding vegetation and any visible human modifications of the riparian zone being important determinants of how the sites are perceived. Obviously, the most preferred stretches are those with lush green vegetation, continuous water flow with visibly low human impacts. The ecological and aesthetic indices have been combined to identify the most degraded reaches along the river, which account for 52% of the total sites. These sites merit attention both in short and long-term for restoration purposes. Although the degradation overall (arising from natural and anthropogenic causes) is not too high at present, we suggest that regular monitoring of the ecological quality of these sites be undertaken in order to preserve both the ecological and aesthetic aspects of the existing riparian vegetation and arrest any further deterioration.