The Solent Forum

Working in partnership for the future

Opportunity Mapping in Southampton Water


Southampton Water is classified as a heavily modified water body (HMWB) under the Water Framework Directive. Such water bodies are unlikely to reach good ecological status due to socio-economic uses. To review how to maximise the Ecological Potential of Southampton Water, the Environment Agency developed an Opportunity Mapping project; this began with the establishment of a list, based on aerial photography, that mapped coastal structures throughout Southampton Water where mitigation (removal, remediation, or in situ ecological enhancement) measures could potentially take place.

The Solent Forum consulted with Southampton Water stakeholders, to get their view on how how we could potentially develop mitigation measures for the identified infrastructure and review some of the opportunities and barriers to in achieving this. View the findings - Opportunity Mapping in Southampton Water - Final Report.

Opportunity Mapping

All the structures identified from the aerial photography were mapped in GIS and an aerial image of each was drawn. Two maps of Southampton Water (north and south) were produced that plot their locations. The work covered the river catchments of Test and Itchen, New Forest and East Hampshire, the River Hamble was not included as it had already been part of a pilot project. We can supply more detailed information on site locations by request to the Solent Forum Office.

Types of Structures Mapped in Southampton Water

Seawalls Tyres Jetties Concrete blocks/pipes/outfalls Wooden posts/structures
Metal wrecks Plastic wrecks Wooden wrecks Concrete slipways Revetments
Rip Rap Walls Moorings/pontoons Quay walls    


The Environment Agency also mapped the Southampton Water habitats to identify what the underlying habitats are for the identified structures.

Solent Stakeholder Consultation

In 2019, the Solent Forum was contracted by the Environment Agency to consult on the structures identified. It was undertaken in three phases:

  1. We contacted and asked those with potential local knowledge of the structures whether they are still in use, if they know whether they have any historical or ecological value and if they can identify the landowner.
  2. Worked with archaeological bodies to establish the best mechanisms to determine how people can identify if structures have historic value, e.g. what to look for and where to go for more information.
  3. Worked with nature conservation bodies/those with experience of ecological enhancement to look at the different types of structures, e.g. slipways, for the different habitat types mapped in Southampton Water, e.g. saltmarsh. Agree general principles on whether it is better to leave structures in situ, remove them, remove and undertake remedial work or identify opportunities for ecological enhancement.

Once this consultation finished, a revised list was drawn up; in the future this list could be used as a basis for ground-truthing and consultation with landowners. Eventually it is hoped that we can identify potential structures for mitigation for developers, local authorities, port and harbour authorities and the EA’s Flood and Coastal Erosion Risk Management who need to undertake mitigation measures for Water Framework Directive Assessments as part of proposed works or development.

Water Framework Directive and River Basin Plans

The purpose of the Water Framework Directive is to establish a framework for the protection of inland surface waters, estuaries, coastal waters and groundwater. The framework for delivering it is through River Basin Management Planning. The Solent lies within the South East Basin River District.

River Basin Management Plans set out the environmental objectives for the river basin district, with a summary of the programme of measures that will be taken to achieve them; the achievement of the objectives is measured against the Ecological Status or Ecological Potential of the water body.

Each River Basin District is characterised into smaller management units known as Water Bodies. The Water Body for this project is the transitional and coastal waters (TraC) of Southampton Water. A transitional water is a surface water in the vicinity of river mouths which are partly saline in character as a result of their proximity to coastal waters but are substantially influenced by freshwater flows. Transitional waters include estuaries and saline lagoons.

A map of the operational catchment for Southampton Water is available to view at

A glossary of terms used in river basin management planning is available at

Achieving Good Ecological Potential

The Environment Agency measures whether a HMWB meets its Ecological Potential or not by:

  1. Identifying the impacts affecting the water body
  2. Identifying the mitigation measures necessary to ensure the hydromorphological characteristics of a water body are consistent with Good Ecological Potential; and
  3. Assessing whether those measures have been taken.

This project seeks to fulfil the second objective above, identifying mitigation measures. Hydromorphological characteristics are the physical character and water content of water bodies. Good hydromorphological conditions support aquatic ecosystems such as water flow, and substrates provide physical habitat for biota such as fish, invertebrates and aquatic organisms.