The purpose of WP3 is to address degraded river systems. The aim of the first deliverable D3.1 was to begin the development of metrics which indicate the impact of hydromorphological degradation on biota  using existing data. The output, an informed choice of key metrics, aims to support the stakeholder decision making processes and their ability to target desired project goals. These indicators of degradation should be viewed as an interim solution while a more comprehensive and tested approach is produced from WP2 and the final system developed will be an integral part of WP6.

Background

The purpose of WP3 is to address degraded river systems and under D3.1 to specifically look at impacts of hydromorphological degradation on ecological status using existing data. The aim of the work was to begin the development of metrics which indicate the impact of hydromorphological degradation on biota. The authors were conscious of the need of stakeholders to both evaluate current condition but also evaluate the success of river rehabilitation projects.

HYMO indicators of degradation

A possible approach for developing a method of evaluating the ecological and morphological conditions of a river influenced by human intervention is presented. The method is based on a source pool of detailed physical parameters and indicators (metrics) that are linked to the data and outputs of other work packages (WP1 & WP2) within the REFORM Project. Depending on the focus of an evaluation (to choose from morphology, vegetation, benthos and/or fish), experts can use these approaches to identify a subset of key indicators from this pool. When using the approach an evaluation is performed comparatively between the benchmark condition of the river and the river condition affected by human intervention. The output, an informed choice of key metrics, aims to support the stakeholder decision making processes and their ability to target desired project goals. These indicators of degradation should be viewed as an interim solution while a more comprehensive and tested approach is produced from WP2 and the final system developed will be an integral part of WP6. The impact of hydromorphological degradation on individual biological Quality elements is reviewed in the subsequent chapters.

Brief overall conclusions

·         There is an acknowledged need among stakeholders that new hydromorphological metrics are required to facilitate site remediation and for reporting at national and European levels.

·         Pressure/ impact data were assembled from across Europe. The task was challenging, but useful information was gathered.

·         For each major hydromorphological pressure, the physical response gradients of rivers was summarised as diagnostic diagrams.

·         For the first time we provide evidence that metrics indicating HYMO impact could be developed from monitoring data on fish and macrophytes.

·         For the first time we demonstrate the potential to derive metrics sensitive to fine sediment.

·         We provide evidence that phytobenthos (diatoms), invertebrates and macrophytes have the potential to be used in combined metrics.

·         We found that many existing macroinvertebrate metrics lack specificity and can provide false positive responses to HYMO pressure, suggesting that disentanglement of multi-stressor responses is critical to good diagnosis.

·         There is evidence that aquatic habitats protected under the Habitats Directive will be increasingly vulnerable to hydrological pressures with the changing climate.

·         Frequently, overlooked topics such as sediment quality and groundwater issues ought to supplement or be included in HYMO assessments due to their potential for explaining variance in biological datasets.

·         Land-use data on a spatial scale beyond the reach scale (corridor and catchment) relates to site-specific macroinvertebrate metrics and could be a more robust way of assessing impacts.