Gabion Application 2 - Revetments
Sandy beach sites suffering periodic moderate to severe erosion where backshore assets are at risk, Well placed gabions provide reasonable fixed defences, Useful for estuary bank protection.
It is useful solution where armour rock is considered inappropriate or too costly. Various forms available. Can be buried by sand and vegetation. Permeable face absorbs wave energy and encourages upper beach stability.
Wire Mesh Gabion Baskets are filled with cobbles or crushed rock. They are filled insitu, often with locally available material and therefore have a relatively low capital cost. Because they are flexible and porous they can absorb some wave and wind energy, thereby reducing the scour problems associated with impermeable sea defences such as concrete seawalls. Gabions can be placed as sloping “mattresses” or as near vertical cubic baskets. The latter are intended for bank or cliff stabilisation and are not normally suitable for use in shoreline situations.
Gabions provide a short term alternative to rock armour structures in areas where large rocks are not available at an acceptable cost, or where long term protection is not appropriate.
The purpose of a gabion revetment is to provide short term (5-10 years) protection from backshore erosion by absorbing wave energy along the dune face. Their application is restricted to the upper part of sandy beaches, since they are not sufficiently durable to withstand regular direct wave action. They should not be installed on shingle beaches because wear and tear will rapidly cause damage to the baskets. As they are porous structures they will tend to trap wind blown sand and allow the growth of vegetation under favourable conditions. This only applies to sloping structures: steep walls of cubic baskets will not attract sand or allow dune vegetation regrowth.
Gabions used in lower energy or estuary situations can use PVC coated wire. Under more active conditions the coating is soon cracked, becoming relatively useless in preventing corrosion. In general galvanised wire of a larger diameter will provide better service than finer non-galvanised wire with a PVC coating.
Regular basket maintenance is required to maximise the life of gabions. Severely damaged baskets should be refilled and closed with new mesh panels. Replacement mesh should be laid over the entire structure if abrasion or corrosion is widespread. Under exposed conditions a maximum life of 10 years should be anticipated, after which time a replacement structure may be required.
Hangxuan provide a wide range of specification wire mesh gabion baskets and mattresses, welcome enquiry.