caa a22 4500 386389209 CHVBK 20180307112108.0 cr unu---uuuuu 161130s1989 xx s 000 0 eng 10.1017/S0269727000010927 doi S0269727000010927 pii (NATIONALLICENCE)cambridge-10.1017/S0269727000010927 Hesp Patrick A. School of Earth Sciences, Macquarie University, North Ryde, N.S.W., Australia, 2109 A review of biological and geomorphological processes involved in the initiation and development of incipient foredunes [Elektronische Daten] [Patrick A. Hesp] The evolution, ecological processes, aerodynamics, and morphology of incipient or new foredunes on the upper beach is reviewed. Four types of incipient foredunes may be distinguished, namely: type 1, those initiated by shadow dune formation within zones of discrete individual pioneer annuals (e.g. Cakile spp.), and perennials (e.g. Spinifex spp.; Ammophila spp.); type 2, those initiated by dunelet or hummock formation within discrete colonies of perennial grasses and herbs; type 3, those initiated by sand deposition within laterally extensive colonies of pioneer seedlings; and type 4, those initiated by sand deposition within a laterally extensive plant rhizome cover. Type 1 dunes are dominated by high, local flow deceleration and 3-D flow separation. Shadow dunes form within and downwind of the discrete plants. If colonised by annual plants, invasion by perennial plants is necessary for survival. Later lateral plant spread and accretion produces hummocky terraces and ridges. Type 2 dunes (dunelets) are characterised by local landward flow deceleration and marginal high velocity side flows. Sand deposition results in the formation of low, discrete, semi-circular convex mounds (seedlings), or more elongate hummocks and mounds (rhizomes). Types 3 and 4 dunes are characterised by laterally extensive, often homogeneous vegetation canopies. High canopies display more rapid landward flow deceleration than low canopies, thus narrow, asymmetric ridges and longer convex ridges result respectively. High plant densities result in rapid down-canopy flow deceleration, maximum traction load retardation and the formation of narrow asymmetric ridges. Dune height decreases and dune length increases as plant densities decrease. Maximum deposition zones occur for each wind velocity range. Whether ramp, terrace or ridge morphologies are formed depends on mode of beach colonisation, plant density and distribution, sand volume, wind speed, and plant species type and morphology. A range of variables which affect foredune morphology and evolution, including plant canopy density, height and distribution, wind velocity, and various ecological environmental processes are examined. Copyright © Royal Society of Edinburgh 1989 Physics and Physical Geography nationallicence Proceedings of the Royal Society of Edinburgh. Section B. Biological Sciences Royal Society of Edinburgh Scotland Foundation 96(1989), 181-201 0269-7270 96<181 1989 96 PRB https://doi.org/10.1017/S0269727000010927 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1017/S0269727000010927 text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- Hesp Patrick A. School of Earth Sciences, Macquarie University, North Ryde, N.S.W., Australia, 2109 NATIONALLICENCE 773 0- Proceedings of the Royal Society of Edinburgh. Section B. Biological Sciences Royal Society of Edinburgh Scotland Foundation 96(1989), 181-201 0269-7270 96<181 1989 96 PRB CC0 http://creativecommons.org/publicdomain/zero/1.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-cambridge