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Bocking Blackwater Local Nature Reserve River Works

After recently completing the river works at Little Waltham meadows, the Essex Biodiversity project have been working on a new river project; this time at Bocking Blackwater local nature reserve in Braintree.

This river project is slightly different to the one just completed outside of Chelmsford, not only is it on a different river, the river Pant. This project focuses on using soft engineering to improve this stretch of river.

One of the key issues facing this section of river is silt input and erosion, silt is one of the key sources of pollution and input of phosphates, it also reduces the oxygen content of the water which is not great for fish.

The relatively bare and species-poor banks do not have the necessary vegetation to support a wide range of insects, breeding birds and other aquatic-dependent animals which are a key function of our rivers. The remaining issues around the lack of vegetation relate back to pollution, reed and other aquatic vegetation are great, natural ways to clean our rivers; they do this by fixing nitrogen and phosphate in their root systems and forcing them down through the mud and soil where they are locked away.

To do this, we will be installing over 500 metres of pre-planted coir rolls, 200 metres of coir pallets and 60 metres of willow spilling over a stretch of river approximately 1.5km long.

Bocking Blackwater | Essex Rivers Hub

The idea of the pre-planted coir rolls and pallets is to help to establish and bring in floristic diversity. Once the plants have established themselves and bedded themselves into the riverbank these rolls and pallets then rot away. The remaining roots and plants then help to tie the bank together reduce the silt inputs and help to remove the pollution and provide the additional habitat for riverine species. A typical assemblage consists of reed, flag iris, purple loosestrife and water mint; all are excellent sources of pollen for invertebrates and are typically found in lowland eastern waters.

Whilst there may be some disruption during the works, access to the area that we are working in will be restricted and is the nature of these engineering projects the site may look a little raw post works (we will be reseeding with a meadow mix before we have moved on). Hopefully in the medium term, this will leave a much better for interesting and diverse river habitat for the local community to enjoy.

The aim was the start this works on the 19thof January; however, works has been delayed until the end of February due to the heavy rain over the festive and New Year period. Updates on this programme will be posted on this website, with hopefully further news once the project is underway.

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The topics below represent the pressures that many waterbodies in the Combined Essex catchment face. They have been divided into six main categories, but it is quite often that these categories can overlap as pressures relate to each other.

Diffuse pollution occurs as water moves across the land or through the ground and picks pollutants. These pollutants can come from a variety of places, including urban and field run off. The pollutants that enter the river can range from sediment to toxins to excess nutrients, meaning that diffuse pollution can cause a whole range of different issues. The variety in these pressure groups means that it is something that can be quite difficult to tackle. It requires groups of people, business and stakeholders to work together in order to solve this problem.

Fish should be able to travel up and down a river freely, allowing them to move and breed in the most suitable habitats for them. It is important that fish populations do not become isolated, as this makes them more susceptible to disease and puts pressure on their survival. Unfortunately, there are often many barriers along rivers that prevent fish from being able to migrate up and down stream. Where barriers have been identified, they will be seen as a ‘pressure’ on a waterbody. Thankfully, there are many solutions now that can be put in place to aid fish passage, even over large barriers.

The flow in a river can vary greatly throughout the year as rainfall and run off can have an effect. This is a natural process. It is when flow is impacted by non-natural processes that it can cause problems. Sometimes, water can be intercepted or removed from a system; this will reduce the flow, therefore changing the habitat conditions. Some species are happy in high energy rivers. This means that when flow is reduced, these species will no longer survive. The opposite of this can occur when excess water is entering a river, for example through increased runoff. Low energy systems then become high energy and displace the species that live there.

A species that is not meant to be found in a particular area is known as an invasive species. Invasive species can be from a different habitat or a different country altogether. Most of the invasive species that we find on our rivers have come from other countries – plants that people have imported for their gardens or animals that have been released for food or by animal rights activists. Control of invasive species requires a lot of time and effort. We are fortunate that we do have a range of methods to manage most of the invasive species that cause havoc on our rivers, but there are still some which we are still struggling to control.

Many of our rivers have been heavily modified over the years as rivers have been used for a wide range of purposes. Physical modification is one of the biggest factors that causes our rivers to be unhealthy. The issues that it can cause range from reducing habitat, preventing migration of mobile species, and even have an effect on the water quality. Where structures and modifications are no longer in use or necessary, they should be removed to allow the river to regain its natural state. Unfortunately, this action is not always taken which means that many of our rivers are over straightened and contain redundant structures. It is possible to return a lot of our rivers to their natural state, through one off projects, but in other cases it is not possible as the river has been changed to protect assets or manage flooding. It is recognised that some modifications cannot be removed without having severe negative impacts both socially and economically.

This is pollution that comes from a single identifiable source. The pollution entering the river could include a whole range of pollutants. Some point source pollution is known about and licences, for example sewage treatment works. Other sources are not licensed, and therefore work needs to be done with landowners to fix the problems that are allowing the pollution to enter the river. Point source pollution is more easily controlled than diffuse pollution as it often only takes one management approach to solve the issue.