A new index for the assessment of hydromorphology in transitional and coastal waters around Ireland

Abstract

In assessing the overall status of individual water bodies the EU Water Framework Directive (WFD) requires member states to assess both ecological and chemical status. The ecological status of transitional and coastal (TraC) waters is based on the assessment of specific biological elements as well as supporting chemical, physico-chemical and hydromorphological elements. Hydromorphology of TraC waters is one of the basic features of marine and coastal ecosystems controlling the presence of biota. Human induced hydromorphological alterations and pressures can damage the ecology and functioning of aquatic ecosystems. Thirteen metrics were developed and combined to form a hydromorphological index, the Hydromorphological Quality Index (HQI). The index categorises a water body into 5 classes. Semi-qualitative and quantitative criteria were used to assign a morphological classification directly related to that of the WFD, i.e., high, good, moderate, poor and bad. Thirty-three transitional and coastal water bodies were assessed using HQI.