.Irlll rn:::. I nf Coastal Research 612-621 Fort Lauderdale, Florida Summer' 1996
Beach-Ridges: A Review
Matthew Taylor and Gregory W. Stone
Department of Geography and Anthropology Louisiana State University Baton Rouge, LA 70803, U.S.A. ABSTRACT _
TAYLOR, MATTHEW and STONE, G.W., 1996. Beach-Ridges: A Review. Journal 0/ Coastal Research. 121:31,612 ,tllllllll:. 621. Fort Lauderdale (Florida). ISSN 0749-020il. ~ A review of the beach-ridge literature is provided with emphasis on those composed of sand. Although confusion in eusss~_~ ?f the literature exists on differentiating beach-ridges from cheniers, both are viewed hen' as morphogenetically distinct. Several models describing the evolution of beach-ridges in diverse coastal settings have bee-n published. Review of =:.; +-- these models indicates that beach-ridges are deposited by swash during high 01' low wave-oncrgy conditions. and may also emerge through aggradation of an offshore bar. Additionally. numerous models emphasize tho role of vegetation and aeolian deposition in the stabilization, accretion, and preservation of beach-ridges. Beach-ridges generally prograde when an abundance of sediment existx and the offshore gradient is low. Sea-level changes do not determine beach-ridge growth, but can nffect the orientation and elevation of beach-ridge Sl'ts in a beach-ridge plain. Interruption, truncation, erosion of beach-ridges. and deposition of youngvr beach-ridges with a different orient.ation and shape may be caused by climate. sea-level, or sediment supply Huctuntions. Thus beach ridges arc utilized in the reconstruction of sea-level. climate, and sediment budget histories. Growth rates of beach-ridges are studied in an attempt. to elucidate rates of coastal progradation. Absolute quan tification of beach-ridge growth rates is limited by the scarcity of reliahle in situ mutt-rial for dating. Growth rates can also be erroneous due to erosion of some beach-ridges making up a lu-ach-ridgt- plain. Thl' study of beach-ridges has progressed from descriptions of their morphology and discussions on bench-ridge orijzin, to t h« use of these land forms in the interpretation of paleo-environments.
ADDITIONAL INDEX WORDS: Bcucli-ridge». chenier». sea-lone}. coastal progradation.
INTRODUCTION plains (at least two subparallel beach-ridges separated by a progradational littoral muddy unit I. Beach-ridge plains are It is the objective of this paper to provide a review of pub composed mainly of ridges without the large intervening lished research conducted on beach-ridges primarily com swales (OTVOS and P]W'E, 19791 Isee Figure 11. As defined posed of sand-size material. Although heach-ridge studies by STAPOI{ (1975), beach-ridges are "linear mound-shaped have been conducted worldwide, a thorough literature review ridges roughly parnlh-lim; the coast. Ridg« crests have ele has not yet been published (JOHNSON, 1919; ALEXANDEH, vations well above mean high tide, and the bottom of the 1969; CARTER, 19861. Beach-ridges are azonal features im adjacent troughs or swalos have elevations not far from mean plying local morphodynamic controls on progradation. Con low tide." TIll' native material comprising beach-ridges is siderable diversity of thought exists regarding modes of usually similar in composition to t.hr- adjacent beach, how beach-ridge construction (REllMAN, 1852~ JOHNSON, 1919; ever, textural differences may Ill' apparent. Bench-ridges are DAVIES, 1961; BI<;AHELLA, 1964: CUHHAY et al., 1967: PSl'TY, progradational landforms occurring in the f()reshore and con 1967; ALEXANDEH, 1969; TANNER, 1970; WH]WIT, 1970; STA sidered the product of wave and wind deposition occurring at POH, 1975; CARTEH, 1986; MASON, 19911. A significant num the upper limit of wave run up 1SAV!\[ :1':, 1959: STAPt lI\, 1975; ber of causative mechanisms have been identified, and used SI :NAMAI(A, 1975; CAKI'EI\, 19861. to elucidate genetic models. In this paper, we carefully review what may be viewed as a disparate group of models with the MODELS OF BEACH-RIDGE ORIGIN objective of identifying common linkages. It is perhaps worthy of note at the outset that confusion in The concept of bench-ridges was first introduced by Red the terminology used to denote beach-ridges and cheniers ex man 11852, 18(4) in his work on shoreline change along the ists. A beach-ridge is dissimilar morphologically and strati south and east coasts of England. This, and subsequent work graphically when compared to a chenier. A chenier is a coast carried out in the latter half of th« 19th and first half of the al ridge, which constitutes a once active beach, composed of 20th century, resulted in earlv models that persist today, al sand and shell overlying muddy, nearsbore, intertidal or though in modified forms. While tho work of Redman (18521 marsh deposits, surrounded by mud flats and marshes (0'1' helped formulate the first causal link between storms and vos and PRICE, 1979). The finer deposits of the swales be beach-ridge development, significant debate arose after the tween the chenier ridges are the dominant facies in chenier exposition of D. W. .Iohnson's text Shore Processes and Shore line Development. in 1919. JOHNSON 119191 debated the im
95131 receioed 17 Noiiember 1994: accepted in reuisioll 15 .J1I1lC 1995. portance of storm-driven waves as a mechanism for beach- A Review of Beach Ridges 613
BEACH RIDGE S LAGOON NORMAL V A• - •••• ••
BASEMENT MSL ... .. B
NORMAL LEVEL ., . c
Figu re 1. Structura l differ en ces betw een beach- ridges and che niers D
(modified from Smart, 1976). NORMAL LEVEL ridge developm ent and, as an a lte rn ative , wrote on the im portance of lower ene rgy swell waves in beach-ridge origin. F _DEPOSITION I'iR\llEROSION Both schools of thought hav e persisted since th ese early writ Figu re 2. Beach-ridge construction according to Psuty, Sediment is de ings and have played a critical role in guiding the mor e recent posi ted in the foreshore durin g "norma l" conditions and subsequent ly re literature. Thus, the development and subsequent modifica worked into beach-ridges by storms or "nortes" (modified from P SU TY , tion of both models are pr esented below. 1967 ).
Beach-Ridge Formation During High Wave-energy Events beaches (CUSHING WOODS and LEAHY, 1983, 1986; MASON , 199 1). Storm wav es were cons ide red by Rf:DMAN (1852) as the sole possibl e mechanism by whi ch shingle could be deposited Construction of Beach-Ridges During Swell Conditions to form ridges. Storm waves of different a pproa ch orienta tions could result in subsequent destructi on of ridges (RED A sign ificant body of literature concludes th at beach-ridges MAN, 1852)_Ting (1936) also stressed the importance of storm a re constructed during mod erate wave conditions and are not waves in th e construction of cobbl e beach-ridges in South storm-rela te d features. In his ea rly writings, J OHNSON(1919) West Jura , Scotland. Although PSUTY (1967) argued that the proposed th e sign ifica nce of swell condit ions to the cons tr uc Tabascan bea ch-ridge plain in th e southe rn Gulf of Mexico tive phase of beach-ridges, whereas storm wav es ini tiate d was constructed by storm waves or "norte s", he noted the a nd maintained ridge ero sion . Evidence delineating the im importance of low wave-energy events during th e s umme r portance of swell conditions first emerged from the Austra when sediment was tra ns por ted to th e nearshore a nd sub lian lit erature in the late 1950's wh ere th e finer detail s of se quently reworked into beach-ridges by larger sto rm waves beach-ridge ori gin were being debated (DAVIES, 1958a; (Figure 2). Psuty's conclusi ons were based on th e internal McKENZI E, 1958; BIRD, 1960; THOM , 1964 ; HAlLS, 1969 ; structure of th e beach -ri dges mainly at one locality: a n inl et WRIGHT, 1970; COOK and POLACH, 1973; SMART, 1976 ; bar/spit. Here landward dipping beds indicated the signifi SHORT and HESP, 1982 ). The Australian literature is some cance of overwash during the construct ive phase. Similar con wh at con fus ing regarding the terminology surrounding clus ions were reached by THOM (1964 ) in a study of prograd beach-ridges. Not un til 1984 was a distinct ion made between ing beach- ridges on Isla del Ca rme n, Mexico. dune or ae olian ridges and pr edominately marine-formed Th e ra te of bea ch-ridge pr ogr ad ation has received consid beach-ridges (HESP, 1984 ). erable attention a nd, as noted by DAVIS (1958a ), s hould be DAVIES (1958b) explained beach-ridge construct ion carefully considered within a geographical contex t, particu through a process of cut and fill, controlled by the dyn amics larly on considering where the early English wri ters (RED a nd cha racte ristics of waves and th eir resulting swash during MAN, 1853; J OHNSON, 1919 ; LEWI S, 1932; TI NG, 1936) made storm and non -sto rm events . According to DAVIES (l958b), th eir observations. These beaches , such as th e Dungeness fill occurs during periods of cons tructional swell waves form Foreland, are comp osed of pebbl es. Thus, even during sto rms, ing a berm. Cut is dominant during periods of eros ive storm it is possible th at material can be depo sited on the u pper waves (Fig. 3). Th e berm is the only constructiona l feature beach despite th e increase in backwash wh ich plays a sign if on t he beach a nd, th erefore, ma y be considered an incipient icant role in rem oving sedime nt offshore on finer-grained beach-ridge (Fig.S). Berm deposition is followed by a period beaches (CARTER, 1988 ). Pebbles, or other coa rse sedime nts of rapid vegetation coloniza t ion which results in beach-ridge on the beach, enhance percolation ra tes leading to increased aggrad ation through aeolian deposition. MCKENZIE (1958) deposition at the limit of wav e run-up . Th e veloc ity of th e refuted the berm as th e nucleus for beach-ridge development, backw ash is severely inhibited thus reducing it s ca pability to a nd stated th at if a berm wa s isolated from the effects of rem ove mater ial deposited during run-up (CARTER 1988 ). Ar wav es, it would undergo ra pid deflation by wind pri or to veg guments supporting th e formation of beach-ridges during etation coloniza ti on a nd stabiliza tion . McKenzie (1958) also high wave-energy events a ppea r convincing on coa rse clastic su ggested that the gently landward dipping slope of a berm
.Iournal of Coastal Research, Vol. 12. No. :3 , 1996 614 Taylor a nd Sto ne
TIMeI' ANNUAL PLANTS (EG.CAKILESPP.) GERMNATEONBACKSHOREAT HIGH SPRINGTIDELINE
Figure 3. The wave/wind model of beac h-ri dge formation proposed by Davies. A: Berm is deposited in times of "fill", B: aeolia n sand accumu lates to form a "beach-ridge",C: anot her berm is built seaward, D: the second ridge is forme d (modi fied from Davies, 1958 ). TiMeI: SPINIFEXSEEDINGS GERMNATE ONBACKS HOREAT HIGHSPRINGTIDELINE
T2" SHADOWDUNESFORMAROUN DPLANTS CREATING A TERRACE SPINIFEX RHIZOMOS is not extreme enough to account for th e hei ght differences BEGINSEAWARD COLON ISATION. between the crest and swale of a beach -ridge. In addition, he postulated that beach-ridges are th e product of vegetation trapping sa nd at th e toe of a foredune resu lting in ridge for mation and aggradation. THoM (1964 ) argued that vegeta tion played no signific an t T2. SEEDLINGS MATURE, INCREAS EIN DENSITY ANDAEOLIAN SANDDEPOSITION OCCURS . , role in the construction of beach-ridges in Tabasco, Mexico; FORMNGA RIDG ERHIZOMeS/ STOLONS COLONISESWALEANDBEAC H', although it enhanced th eir preservation potential. Addition T3 SPINIFEX DOMNATESGROUND COVER ~ N D AEOLIAN SANDDEPOSITION RESULTSINRIDGE ally, THoM (1964 ) proposed a n altern ative to th e DAVI ES FORMATION. - - ,~, (1958) wind/wave model, and th e aeolian/vege ta tion model of / -, , MCKENZIE (1958), a rguing that vegetation could be both a ' ~ <, " <, ""'-I, constructional and pre servational age nt. BIRD (1960), on the , --.... "... - -:::--_--==- --:: oth er ha nd , supported th e Davies model, and stated that a -;:;.:==::_- -- foredune is constructed on top of a berm. Subsequent "cut" T3: SEED INGSARESWASHDEPOS ITED ONTHEBACKSHOREANDRHIZOMOS/ STOLONS removed some of th e sediment from th e foredune to form a EXTENDSEAWARDS TERRAC EFORMS new berm in front of th e old ridge or foredu ne. The sta bili T4/5 . RIDGEBulLDS INPLACE. zation effects of vegetation were stressed by BIRD (1960 ) en han cing further growth of th e ridge, not th e swale, as th e ' ~ " " vegetation colonized th e less sa line cres t. HAILS (1969 ), in his study of the Umina-Woy Woy beach-ridge system in New South Wales, Australia, supported the model of DAVI ES - --' '' ~~~~ (1958b). He ind icated that bea ch-ridges originate as berms 14/ 5: NEW RIDGEFORMS th at are rapidly colonized by vegetation, thus enabling th e ridge to grow in size. Figure 4. Bea ch-ri dge development due to aeolian sediment transport In a review of Australi an beach-ridge literature, HESP and trapping by vegetation (mod ified from I-1ES P. 1984). (1984 ) refuted th e models of DAVIES (1958b ), BIRD(1960), and THoM (1964), and argued th at beach-ridges owe their alignmen t to vegetation forming at the upp er limit of swas h. ies of bea ch-ridge deposits by UI:ST (1957) at the head of Riga Subsequent ridge growth is accomplished by aeolian deposi Bay, Latvian SSR , a lso indi cated that beach-rid ges are tion (Fig 4). Based on work ca rr ied out in New South Wale s, formed primarily by marine processes, Australia, HESP (1984) suggested that th e internal st ru ct ure ind icates an aeolian origin for beach-rid ges, and that th ey Emergent Bar Model appear as relict foredunes. It is a pparent that inconsistencies in Australian literature regarding te rminology has cau sed Drawing on data obt ain ed along th e Parana coastal plain confus ion . More recent research on Australian beach-rid ges of Brazil, BIGARELLA (1965 ) concluded that the emergence of (HAlLS and COSTIN, 1979; BOWAN and HARVEY, 1986), has an offshore bar may play a critica l role in ridge developmen t. tended to emphasize interpretation of beach-ridge pla in evo Bigarella's work shows a strong similarity betw een th e inter lution in terms of sea-level history and sediment supply fluc nal stratification of beach-ridges a nd th e structure of long tuations . shore bars formed in the laboratory, Ther e is, however, a de Extensive work on beac h-ridges was conducted and pub gree of uncertainty about the specific conditions of dep osition. lished in th e Un ited States during the 1960's and 1970's. Re Observations of the Nayar it coas ta l plain, Mexico, by CURRA Y search and conclusions revea l that no perplexing term inology et a 1. (1967) also indicate the potential significance of long exists in th e US literature, a beach-rid ge is consi dered pri sh ore ba r eme rge nce (Figure 5). Th e emergent bar requires marily marine in origin with occasional dune decoration low wave-energy conditions for enlargement and emergence (SAVAG fc, 1959; CURRAYet al., 1967; PSUTY , 1967; MISSIMER, above sea-level. Storm s following immediately after bar 1973; TANNEH, 1970, 1973, 1974, 1987, 1988; TAN NER an d emergence would result in removal of th e sedim ent offshore. STAPOR , 1971, 1972; TAN NER and HOCKETT, 1973; STAPOR, CURRAY et a l. 11967) base this model on the observation that 1971, 1973, 1975; VO N DREHLE, 1973; STAPOR a nd TAN NER, "the average spacing of beach-ridges in the strand plain is 1975, 1977; CHAKl, 1974; FRAS ER and HESTER, 1977). Stud- similar to the dist ance between the submerged bar and the
Journal of Coastal Research, Vol. 12, No. :3, 1996 AReview of Beach Ridge s 615
mechanism of th ese features rem ains un certain (VON DREIl I.E 19731. As can be readil y glea ned from the pr evious discussion, a widely acce pte d model on the origin of beach-ridges does not exist. A basic understanding of beach-ridge form ation and th e surrounding parameters is necessary in order to compre he nd their importance in aiding interpreta tions of depositional en vironmen t such as sea-level, climatic conditions, wave height, sediment source, and sediment transport directions.
PARAMETERS DETERMINING BEACH-RIDGE CONSTRUCTION
J OH NSON ( 919) recognized th e basic parameter s influenc ing beac h-ridge construction. Beach-ridges will be prograded "whe neve r longshore currents of any type bring to th e beach more debris than the waves ther e operating can rem ove" (J OHNSON, 1919 ). J ohn son stated, as is see n in much of the later lite rature (D;-WlES, 1958; BOWMAN et al; 1989), that a Figure 5. Emergent bar model of beach-ridge formation re lia nt on low wave-energy conditions for emer gence above sea-level (modified from sha llow offshore bottom is also necessary to a id the formation CURRAY el al., 1967 ). of shoa ling wa ves which bring th e sediment onshore. Thi s process, JOHNSON (1919) obse rve d, would continue until the offshore profile steepened as the slope equ ilibrated with the existing waves. Moreover, dimension s of beach-ridges, were present bea ch-ridge." Unfortunately, data supporting this controlled by th e size of wave s and rate of sediment supply; findin g in the form of internal bedd ing in eithe r beach-ridges more ra pid sedimentation resulting in smaller beach-ridges or bars, were not reported. (JOHNSO N 1919). Formation and destruction of beach-ridges in the Neth erlands was studied by DOEGLAS (1955 ). He con Beach-Ridge Construction by Swash sidered th at th e direction of the wind was important in con tr ollin g th e sea-level near th e coas t, whi ch in turn influ enced Individual beach-ridge construction in Tab asco was consid currents in th e land and seaward directi on. MCKENZI E 09 58J ered by TANNER and STAPOR (1971) to be the product of point ed to the abunda nce of sediment provided by a fall in swas h. TAN NER and STAPOR (1971) demonstrated th at th e sea-level as an important parameter in beach-ridge form a internal stru ctur e of these beach-ridges, contrary to th e ob tion. He stressed beach-ridge formation is not relia nt on sea serva tions of PSUTY (1967), are low angle, seaward dipping, level fluctu ations, but on abundant sand supply a nd empha planar beds with little aeo lian sands, indicating swas h con sized vegetation as a vital parameter in beach-rid ge building struction. Additionall y, STAPOR and TANNER (1971) refuted and sta biliza tion . a one or two storm constructional scena rio for the ridges be DAVI ES 0958a) correlated storm waves with a "cutting" cau se the internal bedding is highly complicated, indicating process due to enhanced backwash capabilities. He discussed slow growth periods for each ridge. Th eir work suggested the the importanc e of a low gradient inner she lf, an abundance following: 1) beach-ridges are built by processes in the swash of sediment and protection from un refr act ed waves as th e zone; 2) storm waves play no role in beach-ridge developm ent; basic prerequisites for beach-ridge initi ation. NOSSIN (]964), 3) beach-ridges ar e deposited slowly, i.e. not during one high in his work on beach-ridges in Malaysia, conclud ed th at ba wave-energy event; 4) sea-level fluctuations are an imp ortant th ymetry of th e inn er sh elf, th e st rength and direction of parameter in controllin g th e orientation and morphology of wave s a nd curr ents, supply and nature of sedime nt are cru beach-ridge plains, not changes in energy condition; and 5) cial in influ en cing beach-ridge construction. In a study of th e longshore or offshore delivery of sand is responsible for con Urnina-Woy Woy beach -rid ge sys tem, NSW Australia, HAlLS structin g beach-ridges , each process res ulting in different (1969) emphasized tid al ran ge, seasonal changes in the beac h rid ge sha pe and orientation. TANNER and STAPOR (1972) offshore profile , th e configura tion of the adja cent bedrock sta ted th at under constant wa ve conditions, a sm all berm will coast line, and a n a bunda nt supply of sand as vital parame be deposi ted at th e upper limit of swash. If cons tructive ters in beac h-ridge construction. WRIGH T (197 0) investigated waves prevail , seaward progradation and increases in eleva how sediment availability affected the pattern of beach-ridge tion result in beach-ridge development. Formed in th is fash development flank ing the Shoalhaven River delta, NSW, ion, beach- ridges demonstrate predomin a ntly seaward dip Australia, and conclude d th at beach-ridge construction was ping beds. controlled by two variabl es: 1) wave regime governed the geo Abnormally wide beach-r idges of Pleistocene age hav e been graphic orientation of the beach-ridges; a nd 2) proximity to observed in Florida by V ON DREHLE ( 973). Alth ough inter the rive r mouth confluences governed the type and size of nal structures include seaward dipp ing beds similar to th e sed iment supplied to the beach-ridges. Analysis of beach modern rid ges in other parts of Florida, the depositi onal ridge dep osits on the Ca ribbean coast of Costa Rica by NIEU-
J ourn al of Coastal Rese ar ch. Vol. 12, No.3. 1996 616 Taylor and Stone
WENHUYSE and KROONENI3ERG (1994 ) revealed th at periodic beach-ridge progradation is related to sediment supplied by MODEl volcanic eru ptions. During such eruptions, rivers dr aining ...." DEFLATIONSURFACE the Costa Rican Central Cord iller a transport a n abundan ce of sediment to th e coast which is then deposited as beach ~-/ ~~~~~TlO N ridges. , .,f~~:;~ / ~ Elev ati onal change of indi vidual beach-ridges has been vig orously debated, particularly in Australia. THOM (1964) pro cosrr s R ~~:~~ BAR - "\ - _ posed the seawa rd decrease in height of beach-ridges ob BAR BOUNDING ORIGINAL BEACH - - - SURFACES SURFACE served by DAVI ES (196]) may be related to a steady decrease MODE II in availability of sediment and not a fall in sea-level. This SURFACES AVALANCHE AVALANCHE SHELL LAG SWASH contradicts observations made by other authors (JOHNSON, SLOPESHELL B ED D~ LAMNATION ACCUr,ULATlON,_ _ _~_ 1919; D AVIES, 1958; Stap or, 1988), who claimed a reduction in sedime nt supply produces larger ridges as longer periods ~---~~~-- ~ ~~: ; :::;;r.:::==~ ~~"'--~'" - , .~ -- :...;::/~/ /-= --===- are allowed for individual beach-ridge construction. Perhap s CRODUNESS· BEDDING "1- -::":.-- 7~/ --=====- one of the more convincing arguments was forwarded by TAN RIPPLE I LANDWARD NER and STAPOR (1972 ) who viewed wave run-up and beach SEODING RUNNEL SPILLOVER D1PPINGOVERTOP ~~~~~ci LOBE LAMNAE slope as being critical in th e initiation of sediment deposition near th e maximum extent of uprush . Increased wave-energy Figu re 6. Differences between Type 1 an d Type 2 beach-ridges shown levels and tidal ran ge enhance beach-ridge cons truction, th e by tr ansverse section, Magilli gan Foreland. Nor thern Ireland (modified cessation of which will only occur during a phase of reduced from CAHTI'H, 1986). sediment supply (TAN NER a nd STAPOR, 1972). In a later pa per , STAPOI{ (1975) argued that th e eleva tional cha nge within geogr aphically juxtap osed beach-ridge sets, may well reflect (STONE, 1991; STONE an d STAPOR, th is volume). Thi s is ev a sea-level adjustm ent along th e northeast Gulf of Mexico ident through th e truncation an d aeolian capping of th e sea coast. During a regression, new sed imen t sources are made ward-most rid ges. What is appa ren t, although not yet fully available to a lowered wave base. As a tra nsgression begins , documented along thi s coas t, is th at the system has crossed thi s new sediment, deposited near th e beach during the re a sediment-supply thresh old from abundance to scarcity . gression, is reworked int o beach-ridges. During th e abunda nce phase, beach-rid ge progradation oc Studies of MagiJli gan Foreland, Northern Ireland, by CAR cur red through a predomina nt supply of sediment from the TER (1986), demonstrated th at two typ es of beach-ridges are shelf. During th e scarcity phase a reduction in supply from cons tru cted. Type 1 is formed by gradual accretion an d coa the she lfis evident through the cessation of beach-ridge plain lescing of swas h bars by shore norm al sedimen t t ra nspor t; growth. However, th e beach system did not experi ence wide bea ch-ridges constructed in this manner exhibit sea ward dip spread, pronounced erosio n, but rath er its morphology was ping laminae. Typ e 2 involved longshore sedime nt tra ns port tra nsformed by aeo lian deposition into: 1) accretion of the in which beach-ridges form "from the elongation and welding primary dune; an d 2) aeolia n ca pping of beach-ridges by sand of nearshore bars as they pass into adj acen t wave domains." tran sported from rapidly deflating swales, The relationship Landward dipping beds are characteristic of the se beach between sediment scar city, reduction in beach- ridge plain rid ges (Fig . 6). CARTER (\986) suggested that regardless of progr ada tion, a nd th e initia tion of dune-ridge building is also type, beach-ridges are for med under certain condi tions- es reported by UL'ST (1957) from beach rid ges in th e Latvian pecially on prograd ing coasts where sedimen t influx into th e SSR. littoral zone is high . Abundant sediment accumulates in off It is evident in th e North American literature th at a gen shore bedforms whi ch can th en "feed" beach-ridges through eral consensu s exists on the more significant factors influ ons hore transport by waves. encing beach-ridge cons tr uction: abunda nt sediment supply Sim ilar conclusions have been reached elsewhe re wher e in th e nearshore; lower wave-en ergy regimes-although beach-rid ge plains are located in areas where an abundant storm waves ma y not always be destructive; an d fluctu ations lit toral sediment-supply exists. Along th e nor theas t Gulf of in sea -level. It is clearly a ppa rent, however, that while much Mexico, intermittent beach-ridge plain s owe their location to of our kno wledge evolved from the work of W.F. Tanner and a marked decrease in inner shelf slope along th e northwest students at Florida St ate Univer sity, we ar e perh aps bia sed Florida an d Alabama coasts (STON E, 1991; STONE et aI., towa rds a genera lly cons tr uctive. low wave-energy regime 1992; STONE a nd STAPOR, thi s volume). A regional increase and micro-tidal se tti ng of th e Gulf of Mexico. Nevertheless, in wa ve-energy along this coast results in the availability of the Gulf of Mexico is a particularly appropria te set tin g for inn er shelf material for onshore tra ns port from dista nces up elucidating beach-ridge morph odynamics because of th e high to 4km offshore (STONE, 1991). Differential beach-ridge plain preservation potential of beac h-ridge plai ns. particularl y elevations ind icate comp lex sea-level sta nds-sediment avail along th e northeast an d southern Gul f coastlines. a bility relation ships during the Late Holocene (STAPOH, 1975). Howev er, it is apparent that alt hough th e shoreline GROWTH RATES OF BEACH-RIDGES has ma intained sta bility over at lea st th e las t 150 or so yea rs, Growth ra tes of beach-ridges although documented (DA the supply of sediment to the littoral zone has decrea sed vires, 1958a; CURRAY et aI., 1967; CAInE R, 1986), are highl y
.Iournal of Coastal Resear ch. Vol. 12. No. 3, 1996 AReview of Beach Ridges 617 variable. Gen erally, high rates of sediment influx are reflect ed in smaller ridge dimensions, whereas large beach-ridges ind icate periods of reduced sediment availability (JO HNsON, 1919; DAVIES, 1958a l. DAV IES (1958a) emphasized that ra pid dep osition res ulted in low and closely sp aced ridges wit h very regular profiles, whereas slower deposition res ulted in char acteristi cally longer ridges with wider swales and an irregu lar profile. Many studies of beach-ridge gro wth aid ed by C-14 dating have bee n complet ed . CURRAY et a1. (]967 ) used this method to illustrate vari ations in pr ogr ada tional rates of bea ch-ridge Figure 7. Truncating bea ch-ridges in Ba ldwin County, Alab ama. which sets with in the Nayarit beach-ridge plai n. Th is, they sug display differi ng orien ta tions and eleva tions, interpreted by Stapor (1975) gested, indicates fluctuations in the sediment supply, indi as indicative of fluctu ations in sea- level (modified from S TAPOR, 1975). cating that bea ch-ridge building varied between 12 to 16 yea rs for eac h rid ge. Based on radiometric dating, MISSIMER ( 973) calculated a ridge grow th rate of between 8-15 yea rs per ridge a long Sanibel Isla nd, Florida. TANNI<:R and STAPOR beach-ridges. Th e authors in te rpreted the evolution of the (971) and STAPOR 0975,1988, 1991) indicated t ha t beac h-ridge Nay arit stra nd plain in te rms of climatic cha nge, estimating plains undergo complex histories of intermi ttent gr owth re cool/stormier weathe r periods and periods of hotter/cal mer flected by the different orientations of beach-ridge sets. No weather . Beach-ridges on the east side of Hu dson Bay , ac abso lute tim e for individua l beac h-ridge formation is pr o cording to FAIRBRIDGE and HILLAJRE-MARCEL (1977), have posed by STAPOR (988), but he discu ssed, as did JOHNSON a 45 :!:: 5 year cyclicity. Th e relative uniformi ty of this isos (1919 ) and DAVIES (1958), that differ ences in bea ch-ridge tatically-emerged bea ch-ridge plain is a consequence of th e morphology indicate differ ent rates of progradation. Double Hale solar magnetic cycle which influences a 45 year Rates of bea ch-ridge plain progradation can be obta ined interval between major storm cycles in the a rea. usi ng archaeological dating in areas where a well defined HAILS (969) pr oposed that the Umi na -Woy Woy beach lit hic or ceramic chronology exists (STAPO R, 1975; DE rid ge plain, Broken Bay, New South Wales, re flects construc PRATTER and HOWARD, 1977 ). Thi s technique is particularly tion du ring a fall in sea-level in the Holocene. However, usefu l when geologic ma terial for dating is sca rce.Radio car HAlLS and COSTIN (979) presented conclusive evidence from bon dates from habitation sites on a beach-ridge plain south t he pebble beach -ri dges in the Upper Sp encer Cull', South of the Sa vannah River , Geor gia, were use d by DePratter and Australia, that high se a-level a nd wave energies existed in Howard to defi ne progradation of to-km for thi s section of th e Pleistocene and early Holocen e epochs. The orienta tion th e coast over the last 4500 years. and sedimentological com position of these ridges suggest that th ey wer e built under conditions that a re not operative today BEACH-RID GES AS INDICATORS O.F (HAILS and COSTIN, 1979 1. Strong argu ments are presented DEPOSITIONAL-ENVIRONMENTS (STAPO R, 1975, 1988, 1991; TANNE R, 1988; an d STAPOR and Beach-ridges can provide records of past wave regimes, cli TANNER, 1977) against fluctuating wave-en ergy levels as the mate conditions , sediment supply, sediment source, and sea agent forcin g truncation and erosion of beach-ridge sets. STA level change (CURRAYet. al., 1967; STAPOR. 1975; FAIRBRlD paR (]975) sta ted that the continued later a l continuity and GE and H rLLAIH E-MARCEL, 1977 ). J OIINSON (]9 19) distinct differ ence in ele va tions of beach-ridges of known ag es recogn ized that beac h-ridges have va lue as indi cators of re l refle ct fluctuations in sea -leve l with energy conditions re ative sea-level change and proposed tha t beach- ridges becom maining fair ly cons ta nt (Fig 7). The orie ntation of beach-ridg ing progressively higher inland. may indicate isostatic eme r es can as sist in reconstru cting paleo-littoral drift processes gen ce. Bea ch-ridges decreasing in elevation landward. ind i (STAPO R, 1973 1975; TANNER, 1974, 1987 ; STONE, 199 1; cate land submergence. Individual beach-ridge elevations , STONE and STAPOH, thi s volume) . DAV IES (1958a ) st ressed, do not reflect sea-level change be TAN NER(1974, 1987 ) concluded th at ind ivid ual beach-ridge cause elev ation is govern ed by wav e he ight a nd duration of sha pe a nd orientation is a n indica tor of littoral-drift process the construction perio d. DAVIES (1961 ) stated that wher e es and sources of sedimen t. Beach-ridge plain shape may also beac h-ridges reflect changes in sea -level, the evidence will be indicate fluctuations in sediment supply. Sh orter seaward obvious , such as an over all tilt of th e beac h-rid ge plai n. ridges ma y represent a general decrease in sedimen t supply. PSUTY(967) indi cated t ha t the Tabascan beach-rid ge plai n Longer seawa rd ridges ma y be indi cative of a general in demonst rates through truncation and differing orientation of cre ase in sediment supply to th e bea ch-ridge plai n. TANNER each rid ge set, an interruption in th e sequence of deposition. (1974, 1987) su ggested th at parallel or near parallel beach This view is also held by STAf'OR(]975, 1988!, TANNER (1988), rid ges are indicative of shore-nor ma l transport and deposi and CURRAYet a l. (]967 ). CUHHAYet al. (]967) suggested th at tion. Addit ionally, TAN NEH (1974) ind icated th at as beach erosion and tr uncation of older beac h-ridge se ts was a func rid ge taper increases, especially in cases of bi-directional ta tion of climat ic cooling which cau sed a chan ge in wind direc per, th e importance of shore-parallel littoral-drift increases. tion, wave regim e, longs hore drift and thus orientation of Beach-ridge curvature, concav e or convex, according to TAN-
Jou rn al of Coastal Research , Vol. 12. No.3. 1996 618 Taylo r and St one
PRE-HOLOCENE DEPOSITS lI11@~l i~~vi'Wt?i.~~-'~- '-~(,'-iW1!;:m-':: ,;.-.i*tb /S-i*"?,.~. ::,;;R"t&S ~·~';;Pi;';(;j1 ~ ~:.; ~ ".P.R @. -!1.~.,. , L. JE5.EN ~. ~~""Itt"'jj>>'a.SHOALS ~~'. ::: PROGRADATION.!~::=-!~.•" ,.•"."'." "'••. ...E••. .+.EfP.O.. ' I.,T ".•'.' .•..... •'....•...'..:...••...... •."'.,'
S-SHELFMIGRATION OF IN THE HOLOCEN E ;;~ ONSHORE --~""; , • SUBAQUEOUS SAND MASSES DUE TO RATE OF BEACH r --- ~D~ ~T_n~Ns PoRT ~ A RAPID RISE INSEA-LEVEl RELATIVE RID GE SSHOAL - - - -- SHOAL ======~ ______SEA LEVEL CONCAVE (SOURCE) - -- - ...... ' - -- _REFRACTE D(SOU RCE) ______=[: ______SEAWARD I WAVES 1 IN C1DENTW~V~S-- - - RISE 2 -- - - INcIDENTwAvEs-- -
STABLE SEA LEVEL DIMINUTION IN SHOAL SIZE AND REDUCTION IN SEDIMENT TRANSPORTED ONSHORE
FALL IN RELATIVE PRE -HOLOCENE DEPOSITS SEA LEVEL AND REJUVENATION iJIII_ ~ --J~{:::j~il:;~~G~~= N OF INNER SHELF : SEDIMENT INCREASING INNERSHEl F SLOPE ~ - ~t ONSHORE TRANSPORT ~ CESSATIONINBEAC HRIDGE PROGRADATION HOLO CENe " ,;, .,~ l if.,IJj:1L _ - ~ - SOURCE FOR HIG H-PROFILE FOR EOUNE DEVELOPMENT BEACH . \ ~ .....,),,\~ ""'I: TRANSPORT AEOLIAN CAPPING OF BEACHRIDGENUCLEUS RIDGES SHOAL /SO URCE) REFRACTED CONVEX -- - - "" - -Ai': - - - WAVES ONSHORE SEAWARD ------r ------======t ======4 INCIDENT WAVES 3 INCIDENT WAVES
Figure 8,A conceptual model for th e developm ent of concav e and convex sea ward beach-ridge deposits along a low gra dient inner shelf
NER (974), is an indication of features such as headlands, tween beach-ridge sets of disti nctive elevations within a shoa ls, or capes, which affect wave refraction, beac h-ridge plain, Low ku rtosis values (near the Gau ssian K Alt hough the critical links between sea -level and bea ch = 3) are foun d on th e topographically higher ridge sets in ridge development are still deba ted (et' STAPo R, 1975; CAR dicating higher wave-energy, Higher ku rtosis values are rep TER, 1988 ), it is evid ent tha t a reduction in the ra te of sea resentative of topographically lower beach-r idge sets an d re level rise during the mid Holocene per mitted ons hore tr ans duced wave-energy, Cha nges in kurtosis valu es acro ss set port processes to dominate th e littoral system along low-gra boun daries wit h distinctive elev ations indicates a cha nge in dient inn er sh elves, Drawing from th e work OfSTAPOH (1975) wa ve-energy. Variation in wa ve-en er gy levels, TANNER and STONE (19!H) , it is a pparent that cha nges in the geom (1992bl concluded, do not represent fluctu ations in gene ral et ry of beach-ridges along the N,E. Gu lf of Mexico coast can sto rm ines s, bu t are indicative of cha nges in water-level. Rise be partially expla ined by va riations in sea- leve l stands. An in sea-leve l provides a subs tantial increase in wave energy abun dance of sediment on th e inne r shelf in the form of sub along the coast as les s energy is lost from sh oaling waves aqueous shoals may have provided a source of sediment for before breaking, direct tran sport ons hore (Fig, 8), Subsequent seaward pr o MASON (1991) proposed th at beach-ridge complexes are a grada tion of beac h-ridge plai ns would have decreased during "proxy record of climatic fluctuations" and that "differences a period of sea- level stability during which th e inner-sh elf in storm frequency an d intensity explain variations in the slope began increasing. The cessation of sediment supply sedimentation regim e". Additionally, MASON (1993 ) demon from offshore would result in th e development of highe r-pro strated from many exa mples around th e world how archae file foredu nes , transgressing the seaward margin of th e ologica l da ta from coastal settlements can be ut ilized with beac h-ridge plai n, A subsequent fall in sea would be required care to aid in the dating of coastal progradati on of beach to rejuve na te the offshore source of sediment, res ulting in rid ges an d cheniers . Beach-ridges can also be used to help geometric switches from concave seaward to convex beach correlate cultural depo sits in or on beach-ridge plains (MA ridge plai ns (Fig , 8). SON, 1993). CUSHING WOODS and HEALY (1983, 1986) regard TAN NER 0991, 1992a,b, 1993) and TAN NER et al. (1989 ), beach-ridges as significant aid s in underst anding paleo-ge suggested th at useful in formation for reconstru ction of the ography as th e ridges record shoreline position th rough tim e, Gulf of Mexico sea-level curve may be obtained from granu CUSHING WOODS an d HEALY (1986) correlated geographical lometric analysis of beach-ridge sediments. TANN ER (1991) ly separated sets of beach-ridges along the Baja California sta ted that wave-energy den sity in the surf zone is an inverse Norte Coast of Mexico to dem onstrate that the sh orelines function of ku rtosis on ne arly straight beaches. Kurt osis val may have prograded at similar time per iods. MOSELY et al. ue s have been shown by TANNER (1991, 1992bl to vary be- (1 991 ) argued th at beac h-ri dges have imp ortant cultural im-
J ournal of Coastal Research. Vol. 12. No, 3, 1996 A Review of Beach Ridges 619
18 8 STEEPNESS 7 (H'o/T') 6 5 o 0.005 4 o 0.02 3 • 0.06 /:, 0.10 2 o 0.25 " 0.40 R / H'o 1.0 9 8 7 6 5 4
3
2
0.1 1/1/2 1/1 1/2 1/10 1/30 SLOPE
Figu re 9. The relationship between relative wave run-up ( R/H ), beach slope. and deep water wave steepness a nd heig ht (modified from S AVAGE, 1959). plications along the arid Andean Coast and a re ind ica tive of wh ere H, = deep wa ter wav e height, L, = deep water wave "abnormally stressful conditio ns ." The ridges are a conse len gt h, tan [3 = submarine slope, d = me dian or me an di quen ce of major' tect onic eve nts which loosen terrestrial sed ameter of bea ch material , C = constant with a value of 3. imen t. Transport to the coast of th e previou sly re leas ed sed From this equation Su namar a indicated that be ach-ridges iment may occur duri ng later El Nino Southern Oscillation will occur with higher pr obab ility at places having a gentler (ENSO) events whe n abnormally high ra infal l is exp erienced submarine slope, or larger materia l size, othe r factors re in this arid envi ronm ent. These beach-ridges may thus record maining constant. a history of EN SO eve nts during the late Holocen e, a nd coul d Beach-ridge formation mode ls in the lab oratory are simple be significant for EN SO eve nt pre diction. whe n compared to beach-ridge forma tion processes in nature. SAVAG EC1959) stressed th at mod els of beach-ridge constru c BEACH-RIDGE STUDIES IN THE LABORATORY tion do not exactly emulate natur al processes, bu t th ey do embody th e basic pri nciples involved in beach-ridge construc Lim ited work has been conducted on beach-ridge formation ti on and lead to a better understanding of beach-ridge for in the laboratory. In one of the earlies t laboratory studies, mation in nature. SAVAGE (1959) , deter mined the re lationship between re lative wav e ru n-up (RJH), beach slo pe, and wav e steepness in a wave tank . As shown in Figure 9, Savage (1959 ) demon strat CONCLUSIONS ed that run-up increases with decreasin g slope for a given 1) Th e study of beach-ridges ha s progr essed from sim ple wave steepness prior to a rap id decline. In situations where descriptions of their stru cture to utilizing these coastal land the slope achieved by the foresho re of the beach-ridg e does forms to aid in th e in ter pr etatio n of past sea-levels and cli not reach the slope max imum (Fig. 9), the height of beach ma te. ridge s would be governed by the maximum slope of the fore 2) Current models exp laining beac h-ridge evolution suggest shore and run- up. that beach-ridges are formed by swash during high or low SUNAtvlARA (975) concluded that the interaction of swa sh wave-energy conditions, the emergence of offshore bars, or an d bea ch materi al determine beach-ridge construction. This throu gh a comb ination of wav e and win d depositi on. Desp ite mech anism is difficult to observe in nature and in the labo the diversity of model s, explicable given th e azon al nature of ratory due to the complexity of phen omen a in the swash zone. beach-ridges, most model s re quire an abundance of se diment Swash is governed by deep wa te r waves and submarine slope , and a low offsho re gradient as ne cessa ry param eters in so these two factors along with beach materia l must be con beach-ridge plain evolution. sidered in the calculation of an em pirical formula to explai n 3) Absolute rates of individual beach-ridge buildin g are beach-ridge construct ion (SUNAMARA 1975 ), considered "estimates" unti l da ti ng methods improve. Rela H,/Lo = Cttan [3)-0 27 (d/LoY,,;7 0) tive rates of beach-ridge progradation , however, are often in-
-Iourn al of Coastal Resear ch, Vol. 12. No, 3, 1996 620 Taylor and Stone dicated by change in beach-ridge dimensions: Smaller, closely l'rgy Dissipation During tho Late Holocene: Royal Soc. of South spaced ridges indicate rapid progradation; ridges of larger di Australia. v.103. p.169-17:3. HES!', P.A.. 1984, Forcdunc Formation in Southeast Australia. in mensions and greater spacing point towards relatively slower Thom, B.G., cd .. Coastal geomorphology in Australia. Academic rates of growth. Press, Sydney, p. 69-97. 4) Geometry, orientation and elevation of beach-ridge sets HESTEH, N.C., and FI{A~EI1. G.S.. 1973, Sedimentology of a Beach and plains are good indicators of past sea-levels, morphodyn ridge Complex and its Significance in Land Usr- Planning: Illinois Stat" Geol. Surv.. Environmental Geology Notes, #63, 41pp. amic and climatic conditions. JOHNSON, D.W., 1919, Shore Processes and Shoreline Deivloprncnt, Wiley. New York. ,JoIINSON. D.W .. 19611, Shore Ridges and Their Significance. in: LITERATURE CITED Shore Processes and Shoreline Dccclopment, Hafner. New York. LJ.:WIS, W.V .. 19:32, The Formation of the Dungem-s» Foreland: Geo AI.EXANm:H. C.S., 1969, Beach-ridges in Nort.neustcrn Tanzania: graphical .Iournal. v.BO. p.:lO>l-:324. Geographical Review, v.LIX, p.104-122. MASON, O.K. 1991. A Gooarchaeological Methodolo/,'Y for Studying BICAHELLA.•J.J., 1965, Sand-ridge Structures from Parana Coastal Prograding Coastal Sequences: Beach-Ridge Geomorphology in Plain: Marine Geology, v.S, p.2fi9-278. Kotzebue Sound. Alaska, in: Paleoshorcline» and Prcliistorv; ,J(>IIN BIIUl, E.F.C.. 1960, The Formation of Sand Beach-ridges: Australian SON. L.C .. and STHllaIT, M.. (l'ds). CRC Pre',". Boca Raton. Flor Journal of Science, v.22, p.349-350. ida, pp CHHI~T1AN~F:N, BOWMAN, D., C., and MOI{DECKAI, M.. 1989, Late MA~oN. O.K, 199:3, The gpoarchaeology of beach-ridges and chen Holocene Coastal Evolution in the Hanstholm-Hjardemaal Re;,'ion. iors: studies of coastal evolution using archaeological data: Jour NW Denmark. Morphology, Sediments and dating: Geografkisk nal of Coastal Research. v.9( 11, p.12G-146. Tidsskrift. v.89, p.49-57. MI.'iSIMI·:I<. T.M.. 197:3. Depositionu! History of Sanibel l sland. Flor BOWAN, G., and HARVEY. N .. 1986. Geomorphic Evolution of a ida: Coastal Research Notes. v.:1111I, 1'.1:3-14. Beach-ridge Complex, LeFevre Peninsular, South Australia: .Iour MISSIMEI{, T.M .. IY7:1. Growth Rates of Bouch-ridge« on Sanibel Is nal of Coastal Research, v.2(3J. p. :345-:362 lnnd.Florida: Trans. Gulf. Coast. Assoc. Gl'OI. SOl'. v.2:3. p.:38:3-:38B. BI'SEN. KL., 1979, History and Sedimentary Analysis of the Parallel McKENZIE, P., 1>l;'8. TIll' Devclnpmcnt of Beach Sand Ridges: Th Beach-ridges at Hammond Bay, Michigan: Consra] Research. Australian -Iournal of Sci"nl'l" v.20. p.21:1-214. v.51 II, p.5-6. MOC'I':U:Y, IYI.E .. 19>11. Spurt- Shutth- lm.un-rv of Rpcpnt Catustroph CAliTEH. R. W.G., 1986, Thl' Morphodynamics of Bench-ridge For ic Changp Along the Arid Ande.m Coast. in: Polcnshorvlinc« and mation: Magilligan. Northern Ireland: Marine Geology. v.7:l, Prchistorv. ,IOIINC'ON, L.C., and STI
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a Symposium Offered at Florida State University, 1977: Tallahas curve and river delta history, Trans. Gulf. Coast. Assoc. Geol. Soc., see, Florida. Coastal Rosearch and Department of Geology. 315p. -.xi.r. p.583-589. STAPOR, F.W .. MATH":ws. T.O .. and LINFW{l)-KEAI{NS, F.E .. 1988, TANNER,W.F., 1992a. 3000 years of sea-level change. Bulletin of the Episodic Barrier Island Growth in southwest Florida: A Response American Meteorological Society, v.7.'3I.'3I. p.297-303. to Fluctuating Holocene Sea-level": Miami Geological Society TANNEI(, W.F., 1992b. Late Holocene sea-level changes from grain Memoir :3. p.149-202. size data: evidence from the Gulf of Mexico. The Holocene, v.2, STONE. G.W., 1991, Differential Sediment Supply and the Cellular p.249-254. Nature of Longshore Sediment Transport Along Coastal North TANNE\{. W.F.. 1993. An SOOO-year record of sea-level change from west Florida and Southeast Alabama Since the Late Holocene. grain-size parameters: data from beach-ridges in Denmark. The PhD Dissertation, The University of Maryland. 365 p. Holocene, v.31.'3). p.220-231. STONE. G.W., STAP()f{, F.W .. MAY, J.P.. and MOlU;AN, .J.P., 1992, TANNER. W.F.,and STAPO\{, F.W.JR., 1971. Tabasco Beach-ridge Multiple Sediment Sources and a Cellular. Non-integrated. Long Plain: an Eroding Coast: Trans, Gulf. Coast. Assoc. Geo!. Soc., shore drift system: Northwest Florida and Southeast Alabama v.21, p.2.'31-2:32- Coast. USA. Marine Geology, v.l05, p.141-154. TANNER, W.F.. and STAPOl{, F.W., 1972. Precise Control of Run-up STONE and STAPOI{. this volume. A Sediment Transport Model for in Beach-ridge Construction: Z. Goemorph. v.16(4), p.393-399. the Northeast Gulf Coast, Morgan Point. Alabama, to Apalacbi TANNEH, W.F., and HO(']
.Journal of Coastal Research, Vol. 12, No. :3. 1996