Riparian Buffer Zones (RBZ) are patches of land adjacent to rivers, streams and drains, removed from intensive production and containing permanent vegetation. RBZ can provide a variety of environmental and ecological services, including a habitat for biodiversity, enhancing connectivity, alleviating flood threat, water temperature mitigation, greenhouse gas exchanges and aesthetic and recreational services.
From a water quality point of view, RBZ are typically designed such that vegetation in the RBZ increases roughness and infiltration, thus slowing flows and reducing sediment concentrations and mass loads, together with those of particle-associated nutrients and pesticides. The changes within the buffer strip result in a greater resistance to surface flow (as a result of above-ground vegetation) and an increase in infiltration (as a result of the root system). Numerous factors influence runoff dynamics and the efficacy of RBZ, including soil-type, land management/vegetation and topography/slope.
Additional variables such as the width and management of the buffer zone play an important role in determining the buffering effectiveness. Coupled with the width of the RBZ, topography of the surrounding landscape plays a role in determining the effectiveness in removing sediments, nutrient and pesticides, for example through channelling flow into higher energy converging surface flowpaths that leaves insufficient contact with buffers for effective contaminant removal. Hence, large areas of uniform buffer strips rarely experience significant overland flow, thus rendering them obsolete in their effectiveness of restricting the flow of sediment, nutrients and pesticides, whereas smaller areas take all the impact and are often overwhelmed.
Despite their widespread implementation, huge uncertainties remain in relation to the optimal design, management and cost-effectiveness of RBZ as a measure to support the delivery of ecosystem services and to enhance the quality of watercourses particularly at larger catchment scales. Whilst high trapping efficiencies per widths have been reported. It was concluded that it is difficult to arrive at width-recommendations from the literature due to high dependence on site-specific factors.
Buffers have considerable potential for multiple benefits for habitat, flood control, stream shading, greenhouse gas exchanges and potentially recreation. There is an implicit assumption of realisation of buffer functions in catchment plans, but considerable uncertainty in evidence as to how to achieve and assess these. In contrast, buffers also have potential negative perceptions amongst land managers e.g. land take, harbouring weeds and pests, or promoting unwanted access; these must also be addressed to improve uptake by landowners and advisors. This project aims to ensure optimal targeting and management of riparian buffers for the effective management of Irish rivers, and ensure the right measure is in the right place