Essex Rivers Hub

This catchment includes Holland Brook and St Osyth Creek. Holland Brook covers an area of 69.7 km2 and is 19.6 km long. There are two water bodies which flow into the lower reaches of Holland Brook while the Brook itself flows out into the sea. St Osyth Creek does not join Holland Brook and flows into the Colne Estuary.

St Osyth Creek has a Water Framework Directive (WFD) classification of good and therefore is meeting all the requirements needed for good ecological status. Holland Brook however has a WFD classification of moderate and is failing for aquatic invertebrates, morphology, phosphate, ammonia (which are all classified as moderate within WFD), fish and dissolved oxygen (both classified as poor).

Ammonia levels deteriorated from high to moderate in 2012 but the reason for the failure has not been determine and further investigation is needed, also existing data needs to be checked to determine if the failure is correct.

The reasons for the invertebrate and dissolved oxygen failures also need further investigation but dissolved oxygen levels may be impacting on invertebrate populations. Dissolved oxygen levels follow a seasonal pattern with the lowest levels in summer and autumn and the highest levels in spring.

Phosphate failure is linked to both point and diffuse sources. Point sources are the result of discharges from sewage treatment works, private residents and businesses. These discharges need further investigation to determine their impact on phosphate levels and what measures are needed to reduce this impact. Diffuse sources are rural land management in the form of arable farming and animal grazing. More investigation is also needed here to determine the impact and what measures are needed to reduce the impact.

Fish failures have been linked to saline incursion that impacts on an area up to 3 km from the tidal barrier and this reduces the areas many fish can utilise therefore reducing available habitat. Another impact is the introduction of carp, which are dominating the saline area. Their feeding habitats are causing increase turbidity as they stir up the sediment. This is restricting plant growth and covering gravels, which further reduces habitats for other fish species as well as aquatic invertebrates. Another possible impact on fish populations is water levels so water level management needs to be assessed.

Several mitigation measures have been proposed to address issues within Holland Brook but the following have not been taken forward as yet:

  • Increased in channel morphological diversity
  • Improved floodplain connectivity
  • Structures of other mechanism in place and managed to enable fish to access waters upstream and downstream of impoundments

 

 

 

 

 

 

 

 

Website key stakeholders:

Environment Agency logo      Essex Wildlife Trust logo           

Design by LTD Design Consultants and build by Garganey Consulting based on an original concept by Herts and Middlesex Wildlife Trust