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DIY Dune System
When it comes to low cost, self-sustainability, a pleasing appearance and the provision of a valuable habitat, marram dunes cannot be beaten as a form of sea-defence. They have been instituted and used with great success for well over one thousand years. Examples of these can be seen all around the sandy coasts of Europe. The methodology is simple and straightforward, and can be enacted with a minimum of labour and material costs.
The first requirement is a supply of brushwood and/or hedge cuttings. In the days before intensive agriculture hedgerows abounded. They were hand pruned rather than mechanically flailed. Thus a plentiful supply of the base material needed was freely available. Whilst not so plentiful today, some more environmental farmers can supply, or, one can resort to seeking supplies from garden refuse.
Fig.1. The first step is to implant the brushwood into the beach sand in as long a line as possible, at the top of the tide reach. The seaweed surfed to that point will be arrested to gather at the base of the implanted barrier, whilst the dry the wind blown sand will be slowed down sufficiently by the semi-permeable barrier to drop to settle in and behind the twigs.
Fig.2. The next stage is to plant marram grass some 25 cm deep into the sand hill that you (or rather natural forces) have created, leaving the green blades just above ground. Some marram liberated from other hills may have washed up at the base, or, one can carefully dig out small amounts from existing dunes without fear of damage to them. Be sure to go deep enough to ensure the root structure is optimised.
Within a few weeks, even a few days under the right conditions, a stable sand hill as seen in Fig, 2 will have been captured by the twigs, part covering them and gathering behind them ready for the next stage of construction.
Fig.3. Soon you will have a bigger and better dune created with the appearance of Fig.4, increasing rapidly with time to eventually create the high banks we still see some of today along our less damaged coastlines.
Fig.4. The marram will produce its own water supply by the run down of the dew collected by the condensation of damp air coming off the warmer sea each night, rapidly reaching the root system in the porous sand.
It may be necessary to implant more twigs to assist the sand capture, or, you can gently lift those existing by pulling them up slightly. If you are dune building on a popular beach it may prove necessary to protect the dune from people pressure by placing chestnut fencing around it. Not only do children delight in digging into the dune base, but clambering over it too. Even walking on marram three or four times can crush and destroy the root system, so allowing the dehydrated fronds to be blown out by the wind, soon followed by the demise of the dune itself. Marked established pathways may be needed to route people away from the sensitive area.
Sadly, beach draw down by the sand stripping created by offshore demand may mean a higher tide mark bringing in high waves to erode the base of the dune, so leading to undermining and total collapse. Only protection by rock piling can prevent this, although a fronting using large stones can assist the stability to a large degree.
