Title: Management of Vegetation on Raised Embankments
Author: S Runham
Author: F Kirkham
Author: A Sherwood
Author: Environment Agency
Document Type: Monograph
Annotation: Environment Agency Project ID:EAPRJOUT_511, Representation ID: 174, Object ID: 1850
Abstract:
The Environment Agency has a commitment to the management of vegetation on both fluvial and tidal embankments. The Agency aims to ensure that the management regimes implemented are operationally, financially and environmentally sound. The Environment Agency maintains 36,000 km of main river defences nationally and 800 km of sea defences, protecting over two million people and over 850,000 properties from flooding. The protection is provided by earth embankments in the main. The overall project aims are to identify the significance of vegetation type and growing environment on the effectiveness of vegetation management on raised embankments in both fluvial and tidal situations. From 8 to 40 plant species have been identified on raised embankments on individual sites. Most embankments were seeded with a ‘standard mix’ which was considered by managers to be perennial ryegrass and clover, but in fact there have been several broadly similar standard mixes used in EA regions for many years. The uniformity of the vegetation on the embankment has become ameliorated with time. Only 3 out of 25 embankment sections observed had fewer than 10 species. Six embankment sections had over 30 species recorded. There are wide variations in the methods used to manage the vegetation. These ranged from apparently no maintenance (in a nature reserve) to very frequent maintenance (up to 5 mowing cuts per year). The most common was four to five mowings per year. This achieved the standards of the flood defence requirement (100 per cent green cover, a tightly knit root network for bank stability, ease of visual inspection for rapid anticipation of problems to the flood defence). From the project, it was ascertained that the same high standard of maintenance could be achieved from fewer mowings but that this depended on the natural fertility of the soil used to construct the embankment and on seed mix used. It was noted that grazing was used as the vegetation control method in many locations visited. Although this is not favoured by all managers nationally there did not appear to be any compromise to the standards of service required. This method of control was beneficial in terms of biodiversity of plants on the embankment. The management affected greatly the changes in species composition with time. On sites where the species composition was considered ‘species rich,’ or ‘interesting’ it was concluded that past management had influenced this. Many floodbanks were used by the public (even where public access was denied). This caused excess wear and tear at the top of the bank with poor vegetation cover and some signs of soil erosion and lowering of the bank. The use of,different seed mixes (or turfed grass) on the top and sides of the floodbank was not observed in the study, but could be considered for future evaluation.
Publisher: Environment Agency
Subject Keywords: Embankments; Flood control; Vegetation; Brackishwater environment; Marine environment; Freshwater ecology
Extent: 89
Permalink: http://www.environmentdata.org/archive/ealit:4468
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