![]() ![]() Generally speaking, it is believed that under the same conditions, the maximum scour depth of inclined breakwater is less than that of the vertical breakwater the milder the slope, the weaker the wave reflection, and the smaller the scour depth. There is no accepted method to assess the influence of each factor on the scour depth we can only carry out the qualitative analysis. ![]() The scour in front of inclined breakwater is influenced by slope, wave factors, and sediment grain size factors. Where H max is the wave height at the ventral point of wave. It is the aim of this chapter to present and discuss the findings. A range of management techniques have been trialled in south-east England with the potential to benefit declining bumblebees. ![]() The altered mowing of Essex and Suffolk sea walls contributes to the delivery of the United Kingdom government's National Pollinator Strategy, launched in 2014. Rotational (different sections cut each year) and late (annual cut delayed until autumn) cutting are the main pollinator sensitive management regimes undertaken on the south-east coast ( Table 1). 9% of county coastline) in Suffolk ( Table 1). 28% of county coastline) is managed by the Environment Agency (EA), the United Kingdom government's statutory flood defence agency, with pollinator conservation in mind in addition to 23 km (c. Over 132 km of sea wall grassland in Essex (c. sylvarum are likely to continue to decline unless suitable flower-rich foraging habitats, including sea walls, are sympathetically managed ( Dicks et al., 2010). ![]() Rare and endangered bumblebee species such as B. This mowing removes much of the available bumblebee forage resources in one event ( Benton, 2000). Trefoils such as narrow-leaved bird’s-foot trefoil ( Lotus glaber) and clovers such as sea clover ( Trifolium squamosum) are also likely to be particularly favoured where they occur.Ĭoncern has been expressed by some naturalists that sea wall mowing regimes have not been favourable to the conservation of rare insects such as bumblebees, especially where entire sea walls were mown to a short sward height (< 10 cm) in midsummer (July and August). muscorum is probably reliant on a relatively restricted range of flowers found on sea walls, including a number of tall herb species such as black horehound ( Ballota nigra) and spear thistle ( Cirsium vulgare) that can persist in the tall swards of false oat-grass ( Arrhenatherum elatius) and sea couch ( Elytrigia atherica). This species may be restricted to extensive areas of flower-rich grassland in the heart of coastal grazing marsh where it forages on clover and other legumes while complementing these resources with thistles ( Cirsium spp.), brambles ( Rubus fruticosus agg.) and bird’s-foot trefoils ( Lotus spp.) on sea walls. The nest is built at ground level and usually covered by moss, dry grass or leaf litter collected by the bees. muscorum usually emerge between March and May to search for a nest site. muscorum is now primarily a coastal species in the English parts of its range where it is largely restricted to coastal grazing marsh ( Gardiner and Benton, 2011). Brown-banded carder-bee Bombus humilis, credit Tim Gardiner. ![]()
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