Flood protection and erosion prevention. Where do we go from here?

Flood protection and erosion prevention. Where do we go from here?
The severe storms and widespread flooding of winter and early spring 2014 have highlighted the vulnerability of our coastal and low lying communities and the importance of making sure appropriate flood protection and erosion prevention measures are in place.

Break-out panel
XYZ of Landscape & Amenity Product Update reflects on the recent storms and floods which caused so much disruption and asks "what resources can industry provide to help prevent it happening again?"

It is widely recognised that the building and maintenance of adequate protective embankments and erosion prevention measures are crucial priorities if a repeat of the recent devastation to coastal and flood-plain communities is to be prevented.

Engineers and manufacturers have their work cut out to address these challenges and one company at the sharp end of erosion protection and watercourse management is Oxford based Maccaferri.

Best known for the ubiquitous wire mesh Gabion Basket system, the company has developed hugely and is now a world leader in innovative environmental engineering solutions with expertise in erosion control and river training, retaining walls and soil reinforcement, coastal protection, and other related disciplines.

Over recent years the company has provided creative and cost efficient solutions to a variety of water related engineering challenges. Here we take a look at a handful of examples.

Rutland Water
At Rutland Water, the largest reservoir by surface area in England, engineers installed the company's Enkamat A20 erosion prevention matting on the waterside embankment slopes to prevent water scour caused by wind-blown waves.

Enkamat is a high performance, three-dimensional matting made of polyamide monofilaments pre-filled with bitumen bound mineral filter of dense stone chippings. At 22mm thick and with a weight of 20kg/sqm, Enkamat A20's composition and solid mass provides an immediate erosion protection. Its open, woven texture also allows vegetation to grow through its structure, resulting in a naturally vegetated slope within a few months.

The system has been widely used on river or canal banks, lakes and reservoirs throughout Europe and is designed to be resistant to the wave action caused by small ships and pleasure craft passing by.


Boscastle

At the pretty sea-side Devon village of Boscastle, the scene of devastating flash flood in 2004, Engineers Halcrow used over 7000 sq metres of Maccaferri wire mesh, Reno Mattress units and Mac Mat R geomats in planned remedial work to reinforce and protect embankments of the River Valency, which runs through the village to the sea.


Reno Mattresses are large flat wire cages, similar to gabions, lined with filter fabric and filled with site won fill material. At Boscastle, they were overlain with Mac Matt R, a three dimensional mesh reinforced geomat.
Together they create a hard, durable embankment protection system capable of withstanding extreme flow velocities and impact from water-born debris.

Embankment reinforcement
Simplicity, durability and speed of construction have made stone filled Gabions the default material for embankments stabilisation and erosion protection. Their physical mass and open, free draining composition gives them enormous structural strength and resistance to hydrostatic pressure. Here, pre-filled Gabions are placed below and above the waterline to reinforce riverside banking close to an historic stone-arch bridge.


Beach protection
ACBM's or Articulated Concrete Block Mattresses sit at the heavy end of coastal erosion protection measures. At up to 8.30 tonnes in weight, each ACBM consist of a mattress of individual concrete blocks which are secured together with high strength steel cables. When installed they help stabilise and reinforce intertidal zones and mitigate against the scouring effects of wave action.

Coastal containment

MacTubes are giant geotextile tubes designed for building coastal and river structures for erosion protection, containment and dewatering of wet slurries and the reusing of dredged material.


As a "soft" armoured structure, they offer minimal impact to the environment while providing a cost effective alternative to "hard" structures.

MacTubes are designed for use as: revetments - to protect against erosion of shoreline adjacent to existing buildings; as beach protective groins or breakwaters; as dykes - to form a containment area in which to pump dredge spoils; as dune cores and as artificial reefs, installed offshore to replace natural barriers.


Green reinforcement
Where soft erosion protection is required for vulnerable channel banks, Maccaferri provides pre-bundled Coir Logs which can installed at the water-line where they prevent wave action from damaging river or lake banks. They are designed to rapidly re-vegetate and can be supplied pre-planted with established riparian species for instant bank vegetation. The plants quickly trap sediment and soils in suspension in the channel flow, refilling eroded pockets in the existing banking.

Coir Logs contain densely packed coir fibres within either a polymer mesh 'sausage' or within a woven coir mesh, to produce an entirely natural coir log. These bio-degrade over a period of years to leave a stabilised bank of plant biomass.


Emergency hydraulic protection
Hand place sand bags are probably the most recognised and basic tool in emergency flood prevention for homes and commercial properties. At a much larger scale MacBags are non-woven polypropylene geotextile enclosures made in a range of sizes and designed to enable machines to lift the pre-filled bag for into position.

Software
To help engineers model and assess how changes to channel profile and surface characteristics affect crucial flow patterns in rivers, streams and other watercourses, Maccaferri also has a free software package available. The "Macra 1" software package is simple and straightforward to operate and allows users to calculate flow depths in rivers and watercourses and see how altering the channel profile or modifying surface characteristics, such as by adding vegetation or applying protective measures, can affect watercourse performance, instantaneously.

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