Descriptor 7 focuses on permanently altered hydrographical conditions, which predominantly arise from coastal activities causing topographical changes (e.g. land claim, barrages, sea defences) and coastal and offshore infrastructures (e.g. ports, wind farms, oil rigs, pipelines, heat and brine outfalls).

© Fotolia, Author: Halberg
Permanent hydrographical changes can occur due to changes in the thermal or salinity regimes, changes in the tidal regime, sediment and freshwater transport, current or wave action and changes in turbidity. The degree of change and the period over which such change occurs varies considerably, depending on the type of modification. Assessment of the degree of change can be related to both the water column and the sea-floor, and consequently to their biological communities. These types of change are normally triggered by building activities, such as extensions or alterations to the coast, or the building of artificial islands and other infrastructural works in the marine environment (such as outfalls from power stations, bridges and causeways to islands, and offshore installations). This Descriptor addresses all such developments (existing and new infrastructures) including both large- and small-scale structures. The cumulative pressure of 'localized activities' will have to be considered to assess the significance of the aggregated effect of many small-scale changes. Specific importance is given to new planning activities that will have to fulfill Environmental Impacts Assessments (EIA). 

Changes, such as altered erosion patterns or residence time can modify local conditions in a way that negatively impact sensitive species and habitats and can therefore compromise the achievement of the biodiversity and eutrophication Descriptors (D1, D4, D5 and D6). Consequently the cumulative impact on the ecosystem from pressures resulting from the alteration of hydrographical conditions is therefore intimately linked to the assessments of these other Descriptors.
D7 Commission Decision 2010/477/EU
Permanent alteration of hydrographical conditions does not adversely affect marine ecosystems.

Permanent alterations of the hydrographical conditions by human activities may consist for instance of changes in the tidal regime, sediment and freshwater transport, current or wave action, leading to modifications of the physical and chemicals characteristics set out in Table 1 of Annex III to Directive 2008/56/EC. Such changes may be particularly relevant whenever they have the potential to affect marine ecosystems at a broader scale and their assessment may provide an early warning of possible impacts on the ecosystem. For coastal waters, Directive 2000/60/EC sets hydromorphological objectives that need to be addressed through measures in the context of river basin management plans. A case by case approach is necessary to assess the impact of activities. Tools such as environmental impact assessment, strategic environmental assessment and maritime spatial planning may contribute to evaluate and assess the extent and the cumulative aspects of impacts from such activities. It is however important to ensure that any such tools provide for adequate elements to assess potential impacts on the marine environment, including transboundary considerations.

D7 Documents