Caldicot Level - Newport Wetlands NNR EarthCache

The locations visited whilst completing this EarthCache are owned by the Natural Resources Wales (NRW – was Countryside Council for Wales (CCW) when this EarthCache was set up). Permission for this EarthCache has been given by the NRW. The initial permission was for a period of 12 months (from 1 April 2010 to 31 March 2011). This has now been indefinitely extended. However, the permission can be withdrawn at any time should problems occur. All visitors should stick to the designated footpaths. Deviation from the footpaths can be hazardous.

The hazards (from the NRW Site Hazards List for the Newport Wetlands National Nature Reserve (NNR)) include overhead power lines and pylons, underground electricity cable, visibility at entrance to Uskmouth car park, reedbed lagoons, reedbed sluices, contact with effluent in reed beds, pipeline and high voltage electricity unit on seawall, buried pipe carrying waste products, intertidal zone (large tidal range, unstable, muddy substrates dangerous currents), ditches/lagoons (deep water, steep, slippery ditch sides, submerged vegetation), water-borne diseases in ditches and other open water, tidal debris on sea wall, hidden ditches in lagoons, livestock (injury from charging – animals, especially likely in presence of dogs), sea walls and giant hogweed. Whilst this Hazards List was prepared primarily for any contractors working in the reserve they can in the main be avoided by staying on the footpaths and not flying kites.

The NRW granted permission within the following conditions: those that take part are made aware of the status of the Newport Wetlands NNR site (this had been done by the ‘Cache Description'), that due regard is made to other users on the Reserve and that participants only use designated footpaths.

It should be noted that when this EarthCache was set up, some of the aerial maps of the Newport Wetlands NNR were out of date (that is, they do not show some of the footpaths used for this EarthCache).

We recommend that you do not venture out on to any of the mud flats, salt marsh and/or sand bars. There is no need to do so to complete this cache.

3. CACHE DESCRIPTION

The intent of this EarthCache is to explore the Caldicot Level at the Newport Wetlands NNR and learn something about its geology and the impact of man.

The Caldicot Level is an area of low-lying estuarine alluvial wetland and intertidal mudflats on the north bank of the Severn Estuary. The Caldicot Level lies to the southeast of Newport between the River Usk and River Wye and consists of 17,500 acres. It is home to Newport Wetlands NNR.

The Caldicot Level and Wentloog Level (which lies to the southwest between the River Usk and River Rhymney and consists of 8,500 acres) are known collectively as the Monmouthshire Levels or Gwent Levels.

The levels are formed from tidal deposits and alluvium, which have been recurrently inundated and reclaimed from the Severn Estuary by humans since Roman times. They have distinctive patterns of settlement, enclosure and drainage systems belonging to successive periods of use, and are extremely rich archaeologically, with finds from the Mesolithic, Bronze Age and Iron Age periods. They are also an important wetland resource in their own right. Parts have been designated as Sites of Special Scientific Interest (SSSI). They are also registered as a Historic Landscape of Outstanding Historic Interest in Wales.

There have been variations in both land and sea levels in the Severn Estuary since the start of human habitation in the area. The Coldicot Levels have been reclaimed from the sea at different times during the historic period, preserving evidence of distinctive patterns of settlement, enclosure and drainage systems. Because of recurrent phases of inundation and alluviation, there is also a proven potential for extensive archaeological remains. Mesolithic and later remains have been discovered at Goldcliff, and late Mesolithic human footprints at Uskmouth.

One of the most significant finds was of a third century Romano - British boat found at Wilcrick near Magor. The Romans occupied the area from the 2nd to the 4th centuries. In 1878, a boundary stone marking the building of 33 paces of embankment by Roman soldiers was discovered at Goldcliff. Research suggests that, initially, reclamation of the natural salt marsh for farmland began at a few "island" sites within the marshes, such as at Nash and Redwick, before a sea wall was built along the whole coast.

Goldcliff Priory was established in 1113 and together with other major landowners took responsibility for further drainage work in the area. Settlements became established, linked by droveways such as the Whitewall at Magor, and land was gradually reclaimed for pasture and arable use. A large number of Anglo – Norman sites including castles, churches, court houses, manor houses, moated sites and watermills show near-continuous occupation throughout the Middle Ages.

On 30 January 1607, flood caused by either a storm surge or a tsunami resulted in the drowning of an estimated 2,000 people, with houses and villages swept away, an estimated 200 square miles of farmland inundated and livestock destroyed. This was one of the worst natural disasters recorded in Britain. Figure 1 shows the ‘Great Flood’ water level mark on Nash church.

Most of the levels have been the subject of artificial drainage schemes, and the area is criss-crossed by drainage channels, known locally as ‘reens’. Many of these are now managed by the Caldicot and Wentlooge Levels Drainage Board.

In 1531, Henry VI set up Courts of Sewers to improve drainage, but without any powers to oblige landowners to carry out work. In 1884, the Caldicot and Wentlooge Level Act established a new body, the Monmouthshire Commissioners of Sewers, with responsibility for maintaining sea walls and roads in the Levels. The long title of the Act is "An Act to provide for the commutation of the liability of Landowners in the Levels of the hundreds of Caldicot and Wentlooge in the County of Monmouth to maintain sea walls and other works to provide for the making and maintaining of roads in the said Levels and for other purposes."

This was superseded by the Caldicot and Wentlooge Levels Drainage Board in 1942.

The pattern of ditches now found on the Caldicot Level has recently been complicated by the construction of part of the Newport Wetlands NNR (in immediate vicinity of the Newport Wetlands Environmental Education and Visitor Centre (which was opened in March 2008, by TV presenter Kate Humble, and is managed by the RSPB)).

The Newport Wetlands (formerly known as Gwent Levels Wetlands Reserve) is a National Nature Reserve (NNR) and is a partnership between the NRW, Newport City Council and the Royal Society for the Protection of Birds (RSPB) – see Figure 2. Its long list of protective designations (SPA, RAMSAR, SAC and three SSSIs) reflect the importance of the Newport Wetlands NNR both in itself and for the wildlife it sustains.

Wetlands are places that are regularly inundated (in the case of the mudflats at the Newport Wetlands NNR by the rise and fall of the tidal Severn Estuary) or saturated, causing the growth of plants that are specifically adapted to living in wet conditions and the development of characteristic soil features. Consequently a wetland is usually pictured as a watery area with cattails, rushes, and waterfowl. Now think of the scientists who study wetlands, and botanists or biologists probably come to mind. Geology is seldom mentioned in the context of wetland studies, yet geology plays a critical role in understanding wetland dynamics. Three characteristics make wetlands unique -- vegetation, soils, and hydrology. The vegetation is dominated by plants adapted to wet conditions; the soils are developed in water-saturated materials; and sites are either saturated, periodically flooded, or contain permanently standing water.

Wetlands are important because they create products and perform functions for man. Our richest modern soils originally formed in wetlands that were drained for farming. Valuable resources such as coal and peat are mined from the deposits of ancient and existing wetlands. Existing wetlands perform many economically and ecologically important functions, such as storing floodwaters, removing sediment and chemicals from surface water, replenishing groundwater, maintaining low flows in streams, providing wildlife habitat and recreational opportunities, and many others.

The Newport Wetlands NNR was created as part of the compensation for the loss of the Taf/Ely Estuary SSSI mudflats of Cardiff Bay when the Cardiff Bay barrage was built – see Figure 3. Over 65 hectares of reedbeds were planted on what were the nearby power station’s pulverised fuel ash disposal areas. These reedbeds, which account for 10% of all reedbeds in Wales, now attract nationally important numbers of breeding water rail and cetti’s warbler and are the only known breeding site for bearded tit in Wales. At the other end of the Newport Wetlands NNR are saline lagoons, which have become a home to Wales’ first pairs of breeding avocets.

The Newport Wetlands NNR also includes the Crown Foreshore which includes the mudflats and salt marsh south of the reedbeds.

Newport Wetlands NNR is home to otters, water shrews, brown hares and polecats as well as a wide range of dragonflies, moths and butterflies. The pulverised fuel ash near the reedbeds provides a substrate for six species of orchid to flourish as well as scarce plants such as narrow-leaved birdsfoot trefoil, dittander and narrow-leaved everlasting pea.

To complete this EarthCache it will be necessary to explore part of the Caldicot Level by visiting the Newport Wetlands NNR. The Newport Wetlands NNR car park is open every day (except Christmas Day), 9 am to 5:30 pm (you are advised to check, in case of any change, the car park times when you arrive as the gates are locked when it is closed). The RSPB Newport Wetlands Environmental Education and Visitor Centre (which is only on a small part of the land owned by the NRW), has a coffee shop which is open from 10 am to 4 pm. There is no entrance charge.

Ample parking for this EarthCache can be found at N 51° 32.758 W 002° 57.662.

This EarthCache uses maintained paths, which are wheelchair accessible. The paths are level with some gentle slopes and a zig-zag ramp up to the raised level of some of the the reedbeds. A floating pontoon (Figure 4) can be used to form a direct route to/from the East Usk Lighthouse (Figure 5 – which was constructed in 1893) to/from the car park.

Cycling and dogs (except assistance dogs) are not allowed on the RSPB recommended ‘Visitor Route’ used to collect some the logging requirements for this cache – see Figure 6

To complete this EarthCache you need to visit the following locations and answer the question associated with each area visited. Those who use a wheelchair need only answer Questions 1, 4, 5, 6 and 7 as these are on, or very near, the wheelchair accessible RSPB recommended ‘Visitor Route’.

You should be standing near the top of the ramp. If you look towards the RSPB Newport Wetlands Environmental Education and Visitor Centre you can see a significant recent change in how the drainage of this area is managed. What is that change? In the years since this EarthCache was set up this change had blended in very well with the landscape making this a very difficult question to answer without doing some research.

Question 2. Co-ordinates N 51° 32.452 W 002° 57.341 [Open fields]

Whilst walking between the co-ordinates for Questions 1 and 2 look over the countryside to the north (on your left). You can see fields, ditches and grips which go back hundreds of years. The church with the clearly visible spire is in Nash. This land is protected from flooding by, amongst others, the sea defences which you will visit later whilst completing this EarthCache. What do you think is the consequence of this protection with regard to archaeological deposits and geology?

Note: as you approached the co-ordinates for Question 3 you should have started to follow the sea wall. At this point you should make sure that you have read the requirements for Question 7.

At the co-ordinates for Question 3 you will, if you look out towards the Severn Estuary, see a man made wooden structure. What do you think that it was used for? Also, please describe the structures appearance – is it straight, curved, are there any other timber posts near it, etc (this is to ensure that you visited the site).

Look out towards the Severn Estuary whilst walking between the co-ordinates for Questions 3 and 4. You will notice that you are, most of the time, walking past mudflats.

Mudflats are usually described as coastal wetlands that form when mud is deposited by tides or rivers. They are found in sheltered areas such as bays, bayous, lagoons and estuaries. Mudflats may be viewed geologically as exposed layers of bay mud, resulting from deposition of estuarine silts, clays and marine animal detritus. Most of the sediment within a mudflat is within the intertidal zone, and thus the flat is submerged and exposed approximately twice daily. Mudflats are important regions for wildlife, supporting a large population, although levels of biodiversity are not particularly high. They are often of particular importance to migratory birds. In the UK mudflats have been classified as a Biodiversity Action Plan priority habitat.

Within the mudflats there are ‘streams’. What do you notice about the ‘streams’ that are flowing through the mudflats? What direction are they flowing and what shape do they form? You need to be aware that what you see will be affected by the time (tides) and weather conditions before your visit. If you have difficulty in seeing the ‘streams’ include in your log the time and tide level when you visited (check out the tide tables for some help) as well as the weather conditions before your visit.

What is the telephone number on the sign at the East Usk Lighthouse? This question is only here to ensure that you completed the cache by visiting the site and not attempted it by Internet, or other, research.

If you cannot find the sign with the telephone number (it may be obscured by vegetation) look at a nearby information board. The title (in English) is ‘The Severn Estuary: A Mud Larder for Birds’. How many birds are there in the group in the bottom right hand corner of the picture?

Look out towards the Severn Estuary whilst walking between the co-ordinates for Questions 4 and 6. You will notice that the mudflats have given way to salt marsh which is located between the sea wall and the ‘river’ channel.

Just like marshes further inland, salt marshes are also wetlands. Salt marshes develop in the band between the land and sea known as the intertidal zone and serve as the transition zone between the two. They are exposed to water at different times of the day or year. Sometimes the marsh has little water, sometimes it is dry, and sometimes it is very full of water. Their salinity, or salt content, varies depending upon whether they are located right next to the sea or further upstream in the estuary or sound. The water level and salinity level determine which plants and animals make their homes there.

Salt marshes are extremely productive. Microscopic organisms like bacteria, fungi, and algae make their home in the decaying marsh grasses. These decaying plants and micro-organisms are then eaten by fish, worms, and crustaceans, furthering the cycle of decomposition. The plentiful insects provide food for birds and fish.

The vegetation of the salt marsh also provides shelter from predators, especially for young animals that use the salt marsh as a nursery.

A salt marsh usually has a number of zones:

- The Lower Marsh is often submerged under saltwater, and supports the growth of organisms adapted to high salinity and lots of moisture.

- The Upper Marsh is a drier area, where plants tolerate lower salt concentrations.

- The salt pans are small depressions that trap and hold water on a high tide.

- The highest edges of the marsh are only reached by extremely high tides, such as during a storm.

As the salt marsh is located between the sea wall and the ‘river’ channel what do you consider will be the effect of rising sea levels on the salt marsh? Also do you think that the effect is already happening here (give the reason for your answer)? What is the ‘interaction’ between the salt marsh and the sea wall?

Whilst preparing this EarthCache we came across a report that stated that in the next ‘epoch’ (which was 20 years and, at the time the report was written, the 20 years were up in 2025) the existing defences will come to the end of their serviceable life and will need to be replaced. The recommended policy was HTL (Hold The Line). It was stated that ‘HTL will manage the risk of impacts from flooding residential, commercial and industrial assets’. However, the report went on to state that ‘HTL does not guarantee funding to build or maintain current or future defences or to counter sea level rise.’

The Environment Agency now takes responsibility for the sea walls (Figure 7 shows a view along the sea wall looking west towards the East Usk Lighthouse) and the major reens' leaving the Caldicot and Wentlooge Internal Drainage Board to deal with the rest. No longer do local residents take responsibility for the protection of their land and homes, and major developers assume that central government will continually reinforce the sea defences to provide permanent protection for their investment. The inexorable rise in the sea level, emphasises the potential risks of developing land which, but for the quite fragile flood defences, would be covered by water with increasing frequency.

At the co-ordinates for Questions 3, 4, 5 and 6 measure the height of the sea wall using your GPS (you may be surprised at the ‘height’ given by the GPS). Calculate the average height of the sea wall using your own height measurements. Estimate, by looking at the flotsam left along the sea wall (this can be clearly seen whilst walking between the co-ordinates for Questions 3 to 6), the difference between your calculated sea wall height and the ‘high’ tide line. Subtract this value from your sea wall height and arrive at a ‘high’ tide height – which you will need to answer Question 7 below Figure 10.

Now make your way back to the co-ordinates of Question 1. There are several ways to go back to that point, namely: -

- If you continue to follow the sea wall the pathway will eventually loop in land and, unless you are careful not to miss a side pathway (on your right), you will end up back in the car park. This pathway is not as wheelchair friendly as the other routes. If you follow the sea wall you will see further examples of the ‘streams’ in the River Usk estuary and other items in the salt marsh).

- Alternatively you could simply follow the RSPB recommended visitor route (which is wheelchair accessible and you rejoined at the co-ordinates for Question 5). This route will take you past a number of sculptures – see Figure 8.

- Best of all, if you have younger members in your group, make you way back to the East Usk lighthouse and then follow RSPB recommended visitor route. This route takes you over the pontoon bridge and passed several of the reedbed view points – see Figure 9.

As you go away from the co-ordinates of Question 1, and using your ‘high’ tide height, estimate the maximum distance (that is, how far inland) the sea would encroach should the sea wall be breached. Send us your average sea wall height, your ‘high’ tide height and co-ordinates for the estimated extent of the inland encroachment of the sea (you may want to complete this question as you drive away from the car park). The units used for the height values should be metres or feet – do not mix metric and Imperial units. Our intent is to plot the results on a map and up load the map at some date in the future.

Please do not put the answers in your log entry, even encrypted. You do not need to wait for a reply before making your log. However, we request that you email the answers to us on the same day that you make your log. Any logs that do not fulfil all requirements will be deleted.

The following is optional and not a requirement to log your visit. Photographs from your visit are very welcome with your log. Feel free to upload any, except those that assist in answering the Questions, wildlife/plant life/landscape photographs you take during your visit to the EarthCache site.

These links open a new page (or tab) leaving the cache page also open so you can switch between them easily.

To learn more about the Newport Wetlands explore the websites of these organisations: -

Click here to go to the RSPB Newport Wetlands web site.

(Note: The RSPB web site included, at the time that this cache description was prepared, a map of the Newport Wetlands nature reserve.)

Click here to go to the Newport City Council Newport Wetlands web site.

Click here to go to the NRW/CCW Newport Wetlands web site.

Please inform us should these links stop working.