The Influence of Historic Maintenance Dredging on the SPA and Ramsar sites
Theoretically, maintenance dredging has the potential to affect the SPA and Ramsar sites through the following routes:
- Changes in the morphology of the estuary through the removal or redistribution of sediment within the system.
- Increase in levels of suspended sediment during maintenance dredging operations.
- Loss of benthic organisms within the footprint of the dredged area.
- Increasing disturbance.
- Operation of the disposal facilities at Cliffe Pools.
To date, a condition assessment of the SPAs has not been produced by English Nature, it is therefore difficult to comment on whether maintenance dredging is likely to be causing a deterioration in its condition. In the absence of a condition assessment for the SPAs, the SSSI condition assessments have been used. The vast majority of the Benfleet and Southend Marshes SSSI (which only covers a small proportion of the study area) is in unfavourable condition. Within the Thames Estuary and Marshes SPA, Mucking Flats SSSI on the north bank is generally in favourable condition, while some of the saltmarsh units on the south bank within the South Thames Estuary and Marshes SSSI are in unfavourable condition.
Overall it is considered that within the context of the estuarine system, the existing level of maintenance dredging activity is not having a significant effect of the SPAs or Ramsar sites, when the scale of the operations is compared to the high availability of sediment within the system, and when the management procedures already in place to monitor the activities are considered.
It should be noted that there are other activities currently impacting on the European sites under evaluation. In particular, the Mucking Flats SSSI area currently is influenced by the operation of the waste facilities within the site. It should be noted that the cessation of these operations might impact on the value of the site due to changes in nutrient levels derived from outfalls and discharges.