Detecting temporal shoreline changes and erosion/accretion rates,using remote sensing,and their associated sediment characteristics along the coast of North Sinai,Egypt

The variation during 15 years in the shoreline along the North Sinai coast has been determined by analysing TM and ETM true colour Landsat images from 1986 to 2001. The analyses identified erosion and accretion patterns along the coast. The shoreline has advanced west of El Bardawil inlet1, El Bardawil inlet2, and El Arish Harbour, where the wave-induced littoral transport has been halted by jetty construction and beach growth rates are 20,681, 69,855 and 20,160 m²/year, respectively. On the downdrift side of the constructed jetties to the east, the shoreline is retreating and beaches erode at rates of −71,710, −69,968, and −11,760 m²/year, respectively. Sedimentological analyses of beach sediment samples have indicated selective transport of heavy minerals according to their densities and grain sizes. A general correspondence has been found between variation in grain size, sorting and heavy-mineral content of beach sand and the patterns of shoreline changes.     

Morphodynamics of a mesotidal rocky beach: Palmeras beach,Gorgona Island National Natural Park,Colombia

The response of a rocky beach to different possible combinations of hydrodynamic conditions (tides, waves, oceanic currents) has been little studied. In this work, the morphodynamic response to different hydrodynamic forcing is evaluated from sedimentological and geomorphological analysis in seasonal and medium term (19 years) scale in Palmeras beach, located in the southwest of Gorgona Island National Natural Park (NNP), a mesotidal rocky island on the Colombian Pacific continental shelf. Palmeras is an important nesting area of two types of marine turtles, with no anthropogenic stress. In the last years, coastal erosion has reduced the beach width, restricting the safe areas for nesting and conservation of these species. Until now, the sinks, sources, reservoirs, rates, and paths of sediments were unknown, as well as their hydrodynamic forcing. The beach seasonal variability, from October 2010 to August 2012, was analyzed based on biweekly or monthly measurements of five beach profiles distributed every 200 m along the 1.2 km of beach length. The main paths for sediment transport were defined from the modeling of wave currents with the SMC model (Coastal Modeling System), as well as the oceanic currents, simulated for the dry and wet seasons of 2011 using the ELCOM model (Estuary and Lake COmputer Model). Extreme morphologic variations over a time span of 19 years were analyzed with the Hsu and Evans beach static equilibrium parabolic model, from one wave diffraction point which dominates the general beach plan shape. The beach lost 672 m³/m during the measuring period, and erosional processes were intensified during the wet season. The beach trends responded directly to a wave mean energy flux change, resulting in an increase of up to 14 m in the width northward and loss of sediments in the beach southward. This study showed that to obtain the integral morphodynamic behavior of a rocky beach it is necessary to combine information of hydrodynamic, sedimentology and geomorphology in different time scales.     

Berm development on a monsoon-influenced microtidal beach

The mechanisms of berm development along a microtidal-high energy beach is examined. Such a beach with medium-sized sand and monsoon wave-controlled profile at Valiathura, south-west coast of India, is selected for this study. The waves which very rarely fall below 1 m, often exceed 4 m during the monsoon period of May to October. The erosion-accretion pattern of the beach shows a cyclicity and the berm development is mainly due to the onshore migration and welding of longshore bars on to the beach following the monsoon rough season. The stages of berm development in the present microtidal beach are more or less similar to the model presented by Hine for a mesotidal case, except for the following intermediate additional stages. The longshore bar develops due to the erosion of beach when the wave steepness was above 0·04, gets flattened when it falls below 0·04, and then reforms nearer to the shoreline as a swash bar. This reformed bar gets divided and the inner bar gets welded on to the beach, followed by the outer bar developing the berm. During the onshore migration of the longshore bar and berm development the beach face becomes partially reflective with the surf scaling parameter, ε_b between 2·5 and 33. The inshore is dissipative with the inshore surf scaling parameter, ε_s?33. The offshore side of the longshore bar is partially reflective with its surf scaling parameter, ε_bar between 2·5 and 33. The breakers are spilling or plunging. Vertical growth of the berm is mainly due to the changes in swash-limit caused by the variations in wave steepness, breaker height and type. Vertical growth stops when the beach-face attains equilibrium with the grain size-wave energy relationship, and a wave steepness below 0·02 helps to sustain this state.     

Assessment of soil moisture influence on CO2 flux: a laboratory experiment

Accurate measurements to assess the influence of soil moisture on CO₂ flux requires the absolute estimates of soil CO₂ flux. Thus, it was constructed a calibration system where CO₂ with fixed concentration flowed through the different porous material. Previous to measurement, in order to verify the performance and reliability of a closed dynamic chamber, different discontinuous air-mixing rates and times were tested. The CO₂ flux was estimated through sequential lectures and the best fit for flux measurements was obtained taking short readings every 3 min, during a total time of 12 min (R ² = 0.99). The best mixing rate was attained for 250 mL min⁻¹, allowing 25 s of mixing previous to CO₂ extraction for an infrared gas analyzer. The deviation of the measured values for dry sand from the reference CO₂ flux (0.097 and 0.071 g m⁻² min⁻¹) was 5 and 7%. On dry sandy loam soil (SLS) the deviation was 2%. The measured fluxes decreased 73 and 22% with content moisture of 20 and 10% (sand), and 78% with content moisture of 31% (SLS). This work allowed to estimate how much the measured emission rates deviate from the true ones for the specified chamber and sampling conditions.     

Erosion and accretion rates and their associated sediment characters along Ras El Bar coast,northeast Nile Delta,Egypt

Beach profile data, covering the coast of Ras El Bar, northeast Nile Delta, collected during the years from 1990 to 2002 combined with landsat images for the area and sedimentological investigation have been used to identify beach and nearshore seafloor sediment changes. Along the coast of Ras El Bar, two accretion sectors and one of erosion have been recognized. The first accretion sector is located west of Damietta harbour, where the harbour jetties have halted the littoral transport, while the second one is behind a system of detached breakwaters protecting Ras El Bar resort. Both the two sectors are characterized by growing shoreline with maximum rates ∼15 and 10 m/year, respectively. Also, they have maximum nearshore seafloor accretion rates of ∼18 and 22 cm/year, respectively. The erosion sector is located east of Damietta port and has a maximum rate of shoreline retreat ∼−10 m/year. Erosion of its nearshore seafloor is indicated recording a maximum rate of ∼−20 cm/year. The rate of net sediment volume change in the area indicates shifting of the accretion sector (II) westward, responding to installation of the new breakwaters unit. The two accretion sectors are characterized by dominance of moderately sorted fine sands in their shore area which change seaward into less sorting very fine sands. Beach sands of the eroded sector are poorly sorted medium grain size. The dominant constituents of heavy mineral species in beach and sea-bottom sands are the characteristic assemblages of the Nile deposits. The sands of the eroded zone are relatively enriched in monazite, zircon, tourmaline, garnet, and rutile.     

Coarse‐sand beach ridges at Cowley Beach,north‐eastern Australia: Their formative processes and potential as records of tropical cyclone history

Storm surges generated by tropical cyclones have been considered a primary process for building coarse‐sand beach ridges along the north‐eastern Queensland coast, Australia. This interpretation has led to the development of palaeotempestology based on the beach ridges. To better identify the sedimentary processes responsible for these ridges, a high‐resolution chronostratigraphic analysis of a series of ridges was carried out at Cowley Beach, Queensland, a meso‐tidal beach system with a >3 m tide range. Optically stimulated luminescence ages indicate that 10 ridges accreted seaward over the last 2500 to 2700 years. The ridge crests sit +3·5 to 5·1 m above Australian Height Datum (ca mean sea‐level). A ground‐penetrating radar profile shows two distinct radar facies, both of which are dissected by truncation surfaces. Hummocky structures in the upper facies indicate that the nucleus of the beach ridge forms as a berm at +2·5 m Australian Height Datum, equivalent to the fair‐weather swash limit during high tide. The lower facies comprises a sequence of seaward‐dipping reflections. Beach progradation thus occurs via fair‐weather‐wave accretion of sand, with erosion by storm waves resulting in a sporadic sedimentary record. The ridge deposits above the fair‐weather swash limit are primarily composed of coarse and medium sands with pumice gravels and are largely emplaced during surge events. Inundation of the ridges is more likely to occur in relation to a cyclone passing during high tide. The ridges may also include an aeolian component as cyclonic winds can transport beach sand inland, especially during low tide, and some layers above +2·5 m Australian Height Datum are finer than aeolian ripples found on the backshore. Coarse‐sand ridges at Cowley Beach are thus products of fair‐weather swash and cyclone inundation modulated by tides. Knowledge of this composite depositional process can better inform the development of robust palaeoenvironmental reconstructions from the ridges.     

Evaluation of criteria for predicting erosion and accretion on an estuarine sand beach, Delaware Bay, Jew Jersey

Predicting erosion and accretion of sand beaches in estuaries is important to managing shoreline development and identifying potential relationships between biological productivity and beach change. Wave, sediment and profile data, gathered over twenty-nine days on an estuarine sand beach in Delaware Bay, New Jersey, were used to evaluate the performance of four criteria that predict beach erosion and accretion due to wave-induced cross-shore sediment movement (Dean 1973; Sunamura and Horikawa 1974; Hattori and Kawamata 1980; Kraus et al. 1991). Each criterion defines a relation, between a wave and sediment parameter, and includes a coefficient that discriminates beach erosion and accretion events. Relations, based on small-scale laboratory and field data, were evaluated for predicting erosion or accretion at the study site. Significant wave heights at the study site, monitored near high water, ranged from 0.08 to 0.52 m with periods of 2.4 to 12.8 s. Median grain sizes of sediments on the beach foreshore, gathered at low water, ranged from 0.33 to 0.73 mm. All four criteria showed a clustering of erosion and accretion events. Relations derived from small-scale laboratory data were better predictors of erosion on the profile at the field site than those derived from field data gathered on exposed ocean environments. The planar profile and dominance of incident waves of low height and short period are similar to laboratory conditions characterized by initial planar beach slopes and monochromatic waves. Decreasing the value of the empirical coefficient to account for the differences in the magnitude of wave energy and grain size increases the performance of the criteria tested to predict erosion of the profile.     

Cross-shore distribution of longshore sediment transport rates on a barred non-tidal beach

This study was conducted to relate the cross-shore distribution of longshore sediment transport and grain size characteristics to cross-shore and longshore current velocities on a sandy low-energy beach in a non-tidal embayment of the Baltic Sea. Simultaneous measurements of current velocities and amount of sand caught in streamer traps were made on 31 sampling runs on 6 d in April 1999 at three fixed sites including the swash zone on the upper foreshore, the lower foreshore, and the crest of the most landward of four bars. Spilling waves broke frequently on the bar but rarely on the lower foreshore, even during onshore wind speeds up to 11.0 m s⁻¹. Waves always broke as plunging waves at the step at the base of the upper foreshore and were converted directly into swash. The greatest longshore current velocities in the swash occurred when wind speeds and water levels were greatest, but wind direction was nearly directly onshore. Longshore velocities were greater in the swash zone than at other sites except when relatively strong winds blew nearly parallel to the shoreline, causing a pronounced wind-induced current at the other two sites. Calculated longshore shear stress and rate of sediment trapped were highly correlated on the bar (r=0.90), less highly correlated in the swash zone, and least highly correlated (r=0.66) on the lower foreshore. Mean trapping rates in the swash were 14.6 times greater than on the lower foreshore and 7.2 times greater than on the bar. Greater trapping rates in the swash are attributed to the greater turbulence mobilizing sediments in the uprush and backwash. Little of the finer-grained sediment on the offshore sites was reworked under low energy conditions. The study reveals the dominance of swash transport on steep, reflective, low-energy beaches where wave energy dissipation takes place over small distances on the upper foreshore.     

Experimental control of beach face dynamics by watertable pumping

The dynamic sediment budget on the intertidal face of sandy surf beaches is influenced by interaction of swash/backwash flows with the beach watertable. Watertable height variations are coupled to tides and pass into the beach as a slow wave of diminishing amplitude and increasing lag. High-frequency pulses from the onshore wave train also propagate into the beach. The height at which the watertable outcrops on the beach face is affected by antecedent tide and wave history and influences balance of sand deposition and entrainment during swash and backwash. Experimental lowering of the watertable by pumping an array of wells induces sand deposition. Energy expended in pumping is less than 0.3% of the onshore flux in the wave train.     

Short-term morphological change and sediment dynamics in the intertidal zone of a macrotidal beach

This paper describes the morphological and sedimentological evolution of a macrotidal beach over a 20 day period under varying hydrodynamic conditions (significant breaker heights of 0·3–2 m and tidal ranges of 2–5 m). During the field campaign, an intertidal bar developed around the mid‐tide level, migrated onshore, welded to the upper beach and was then flattened under energetic wave conditions. The bar had a wave breakpoint origin and its formation was triggered by a reduction in tidal range, causing more stationary water‐level conditions, rather than an increase in wave height. Most of the onshore bar migration took place while the bar was positioned in the inner to mid‐surf zone position, such that the bar moved away from the breakpoint and exhibited ‘divergent’ behaviour. The depth of disturbance over individual tidal cycles was 10–20% of the breaker height. Such values are more typical of steep reflective beaches, than gently sloping, dissipative beaches, and are considered to reflect the maximum height of wave‐generated ripples. The grain size distribution of surficial sediments did not vary consistently across the beach profile and temporal changes in the sedimentology were mostly unrelated to the morphological response. The lack of clear links between beach morphology and sedimentology may be in part due to shortcomings in the sampling methodology, which ignored the vertical variability in the sediment size characteristics across the active layer.     

Characteristics of an open coast tidal flat: Example from Daman,west coast of India

This study highlights lithofacies and biofacies characteristics of the open coast tidal flat near Daman on the eastern flank of Gulf of Khambhat. Sedimentological and biological observation record six facies within the tidal flat area including older beach, beach face, sand flat, mud flat/mixed flat, sand bar and beach rock. Distinct sedimentary structures, foraminiferal assemblage and bioturbation intensity characterize each facies. A wide variety of wave and current generated sedimentary features characterize the sand flat facies. Semiconsolidated sands of older beach running parallel the coastline at a level higher than the present beach face possibly records the latest sea level highstand. The beach rock reflects early cementation of sands in tropical environments. Foraminifera are widely distributed in sand flats, mixed flats and mud flats and grouped into two biofacies — Ammonia-Elphidium-Quinqueloculina biofacies (sand flat and mixed flat) and Trochammina-Miliammina biofacies (mud flats). The beach face and sand bar facies contain forminifera reworked from sand flat and mud/mixed flat. Seasonal variation in depositional style is marked by deposition of fresh mud deposited over large areas of the intertidal flat during monsoon time, most of which is washed away by waves and current actions well before the onset of the next monsoon.     

Changes in beach water table elevation during neap and spring tides on a sandy estuarine beach, Delaware Bay, New Jersey

A field investigation of temporal and spatial changes in wind and wave characteristics, runup and beach water table elevation was conducted on the foreshore of an estuarine beach in Delaware Bay during neap (April 9, 1995) and spring (April 16, 1995) tides under low wave-energy conditions. The beach has a relatively steep, sandy foreshore and semi-diurnal tides with a mean range of 1.6 m and a mean spring range of 1.9 m. Data from a pressure transducer placed on the low tide terrace reveal a rate of rise and fall of the water level on April 16 of 0.09 mm s⁻¹ resulting in a steeper tidal curve than the neap tide on April 9. Data from three pressure transducers placed in wells in the intertidal foreshore reveal that the landward slope of the water table during the rising neap tide was lower than the slope during spring tide, and there was a slower rate of fall of the beach water table relative to the fall of the tide. Wave heights were lower on April 9 (significant height from 17.1 min records <0.16 m). The water table elevation was 0.08 m higher than the water in the bay at the time of high water, when maximum runup elevation was 0.29 m above high water and maximum runup width was 2.0 m. The elevation of the water table was 0.13 m higher than the maximum elevation of water level in the bay 74 min after high water, when wave height was 0.12 m and wave period was 2.7 s. The use of mean bay water level at high tide will underpredict the elevation of the water table in the beach, and demarcation of biological sampling stations across the intertidal profile based on mean tide conditions will not accurately reflect the water content of the sandy beach matrix.     

Hurricanes 2004: An overview of their characteristics and coastal change

Four hurricanes battered the state of Florida during 2004, the most affecting any state since Texas endured four in 1884. Each of the storms changed the coast differently. Average shoreline change within the right front quadrant of hurricane force winds varied from 1 m of shoreline advance to 20 m of retreat, whereas average sand volume change varied from 11 to 66 m³ m⁻¹ of net loss (erosion). These changes did not scale simply with hurricane intensity as described by the Saffir-Simpson Hurricane Scale. The strongest storm of the season, category 4 Hurricane Charley, had the least shoreline retreat. This was likely because of other factors like the storm's rapid forward speed and small size that generated a lower storm surge than expected. Two of the storms, Hurricanes Frances and Jeanne, affected nearly the same area on the Florida east coast just 3 wk apart. The first storm, Frances, although weaker than the second, caused greater shoreline retreat and sand volume erosion. As a consequence, Hurricane Frances may have stripped away protective beach and exposed dunes to direct wave attack during Jeanne, although there was significant dune erosion during both storms. The maximum shoreline change for all four hurricanes occurred during Ivan on the coasts of eastern Alabama and the Florida Panhandle. The net volume change across a barrier island within the Ivan impact zone approached zero because of massive overwash that approximately balanced erosion of the beach. These data from the 2004 hurricane season will prove useful in developing new ways to scale and predict coastal-change effects during hurricanes.     

Spatial and temporal variations of sediment size on a mixed sand and gravel beach

Mixed sand and gravel beaches have been the subject of comparatively few studies in the UK. This paper describes the sediment distribution before, during and after a programme of beach nourishment along a section of mixed sand and gravel beach forming part of the Pevensey Bay Coastal Defences, in East Sussex, UK. The beach was recharged in September 2002, and beach profiles were measured along three cross-shore transects from August 2002 to February 2003. Sediment samples were taken along the transects between August and November 2002, and a total of 147 sediment samples were analysed, 40 before nourishment and 107 after nourishment. The majority of the sediment samples were strongly bimodal, with mean sizes varying between a minimum of 0.18 mm (2.48 ?) for the sand fraction and a maximum of 27 mm (− 4.74 ?) for the gravel. The recharge material was also bimodal but contained more fine sediment than the natural beach material, particularly on the upper beach. The recharge sediment had grain sizes and sorting similar to some of the natural material but lower bimodality parameters than any of the natural sediment. The sediment distributions after recharge contained significantly more fine sediment, particularly on the upper beach. Over time, the beach profile lowered and fine sediment appeared to be selectively transported seawards from the beachface.     

Analysis of the spatial and temporal changes in soil CO<Subscript>2</Subscript> flux in alpine meadow of Qilian Mountain

Field experiments on the CO₂ flux of alpine meadow soil in the Qilian Mountain were conducted along the elevation gradient during the growing season of 2004 and 2005. The soil CO₂ flux was measured using the Li-6400-09 soil respiration chamber attached to the Li-6400 portable photosynthesis system. The effects of water and heat and roots on the soil CO₂ flux were statistically analyzed. The results show that soil CO₂ flux along the elevation gradient gradually decreases. The soil CO₂ flux was low at night, with lowest value occurring between 0200 and 0600 hours, started to rise rapidly during 0700–0830 hours, and then descend during 1600–1830 hours. The peak CO₂ efflux appears during 1100–1600 hours. The diurnal average of soil CO₂ efflux was between 0.56 ± 0.32 and 2.53 ± 0.76 μmol m⁻² s⁻¹. Seasonally, soil CO₂ fluxes are relatively high in summer and autumn and low in spring and winter. The soil CO₂ efflux, from the highest to the lowest in the ranking order, occurred in July and August (4.736 μmol m⁻² s⁻¹), June and September, and May and October, respectively. The soil CO₂ efflux during the growing season is positively correlated with soil temperature, root biomass and soil water content.     

Natural radioactivity measurements in beach sand along southern coast of Orissa,eastern India

The beach placer deposits in the southern coastal Orissa, India may have significant levels of radiation due to the presence of Th and U bearing minerals such as monazite and zircon. In this study, Gopalpur and Rushikulya beach regions were selected to study the ambient radiation environment. The average activity concentrations of radioactive elements such as ²³²Th, ²³⁸U and ⁴⁰K of beach sand samples were measured by γ-ray spectrometry using a HPGe detector, and found to be much higher than the internationally accepted values. The cross plots of eTh/eU and eTh/K inferred that the sand samples of Gopalpur and Rushikulya beach placer deposit were deposited in leached uranium and an oxidising environment. The absorbed γ dose rate levels of the study areas are similar to other monazite sand-bearing HBRAs of southern and southwestern coastal regions of India and of world. Different radiation hazard indices were estimated for the present study area and were found to be much higher than the internationally accepted values. Hence, Gopalpur and Rushikulya beach placer region can be considered as a high background radiation area and a potential zone for radiogenic heavy mineral exploration.     

Wind action and sand movement near Holkham Bay,North Norfolk Coast,England

In Holkham Bay, North Norfolk Coast, England, a wide beach and coastal dunes have formed as a result of wave action and wind activity. This article describes the experiments and field observations that were carried out to explore the nature of wind activity that is presently affecting the morphology of the beach and dunes.The experiments and field observations indicate: (1) Sand is blown off the beach surface very soon after it is exposed during the low tide if the wind velocity is above 3.0 m/sec. (2) Winds from the south, east, and west in Holkham Bay are offshore winds and do not exert much influence on dune formation in the area. (3) The dominant winds (those that exert most marked effect on the beach and dunes) are the northerly, northeasterly and the northwesterly winds. (4) The average annual accretion rate of sand by the wind on the beach is about 3,600 m³. (5) Knowing the annual accretion rate and the volume of aeolian dunes, it is possible to determine their relative ages.     

Natural and anthropogenic influences in the northeastern coast of the Nile delta,Egypt

Landsat enhanced thematic mapper imagery (ETM) of 2002 and aerial photography of 1955, combined with published charts and field observations were used to interpret coastal changes in the zone between Kitchener drain and Damietta spit in the northeastern Nile delta, previously recognized as a vulnerable zone to the effects of any sea level rise resulting from global warming. The interpretation resulted in recognition of several changes in nine identified geomorphological land types: beach and coastal flat, coastal dunes, agricultural deltaic land, sabkhas, fish farms, Manzala lagoon, saltpans, marshes and urban centers. Reclamation of vast areas of the coastal dunes and of Manzala lagoon added about 420 km2 to the agricultural deltaic land. About 48 km2 of backshore flats, marshes, salt pans and Manzala lagoon have been converted to productive fish farms. The main urban centers have expanded; nearly 12.1 km² have been added to their areas, and new urban centers (Damietta harbor and the New Damietta city) with total area reach of ~35.3 km² have been constructed at the expense of vast areas of Manzala lagoon, coastal dunes, and backshore flats. As a consequence of human activities, the size of Manzala lagoon has been reduced to more than 65%. Shoreline changes have been determined from beach profile survey (1990–2000), and comparison of 1955 aerial photographs and ETM satellite image of 2002 reveal alongshore patterns of erosion versus accretion. The short-term rate of shoreline retreat (1990–2000) has increased in the downdrift side of Damietta harbor (≃14 m/year), whereas areas of accretion exist within the embayment of Gamasa and in the shadow of Ras El Bar detached breakwaters system, with a maximum shoreline advance of ~15 m/year. A sandy spit, 12 km long, has developed southeast of Damietta promontory. These erosion/accretion patterns denote the natural processes of wave-induced longshore currents and sediment transport, in addition, the impact of man-made coastal protection structures.     

Effect of source width and tidal elevation changes on aeolian transport on an estuarine beach

Data from a moderate energy, meso-tidal beach on the east side of Delaware Bay, New Jersey, USA, revealed the significance of both beach width as a source for aeolian transport and the effect of tidal rise on source width. Wind speeds averaged over 17·1 min, recorded 6 m above the crest of a 0·5 m high dune, ranged from 11·6 to 12·7 m s^?1 during the experiment. The highest observed rate of transport on the beach was 0·0085 kg m^?1 s^?1, monitored at rising low tide when the average wind speed was 11·6 m s^?1 across 0·35 mm diameter surface sediments. The wind direction was oblique to the shoreline, creating a source width of 34 m. The reduction in the width of the beach as a source for aeolian transport during rising tide was approximately arithmetic, whereas the reduction in volume of sediment trapped was exponential. Aeolian transport effectively ceased when source width was less than 8 m. Wind conditions, moisture content of the surface sediments and presence of binding salts did not appear to vary dramatically, and no coarse grained lag deposit formed on the surface of the beach. The decrease in rate of sediment trapped through time in the tidal cycle is attributed to differences in source width. Sediment deposited in the litter behind the active beach by strong winds during the rising tide was eroded during the high water period by the high waves and storm surge generated by these winds, and net losses of sediment were observed despite initial aeolian accretion.     

Application of wave transformation models for estimation of morphological changes at Vellar estuary,southeast coast of India

Assessment of the wave climate at near coast is vital for estimation of morphological changes, such as growth of sand spit and associated siltation of tidal inlets. Vellar (bar-built) estuary is one of the prominent estuaries along the southeast coast of India, located at 11°30′N and 79°46′E, less studied in terms of its morphological features. The inlet of Vellar is exposed to high energetic waves, inducing large sediment transport rates and shoreline changes. Local wave characteristics are not accurately defined and the available wave information at near coast is limited (point based observations). In the present study, three decoupled numerical models are employed to derive the monthly nearshore wave climate at Vellar by transforming waves from deep water to nearshore. These models are independently validated with buoy observations in deep water and wave gauge data at nearshore. Based on the nearshore wave data, littoral drift along the coast was estimated and compared with the spit growth at Vellar inlet. The estimated average littoral drift along this coast from February to October is 1.93 × 10⁶ m³ toward north and from November to January it is 1.52 × 10⁶ m³ toward south, resulting in a net northerly drift. Results indicated that increase in the wave energy during the period of July to September is responsible for the maximum growth of the sand spit observed in the field.