Loss Of Sand Research Articles

Multidecadal analysis of beach loss at the major offshore sea turtle nesting islands in the northern Arabian Gulf

Undocumented historical losses of sea turtle nesting beaches worldwide could overestimate the successes of conservation measures and misrepresent the actual status of the sea turtle population. In addition, the suitability of many sea turtle nesting sites continues to decline even without in-depth scientific studies of the extent of losses and impacts to the population. In this study, multidecadal changes in the outlines and area of Jana and Karan islands, major sea turtle nesting sites in the Arabian Gulf, were compared using available Kodak aerographic images, USGS EROS Declassified satellite imagery, and ESRI satellite images. A decrease of 5.1% and 1.7% of the area of Jana and Karan islands, respectively, were observed between 1965 and 2017. This translated to 14,146 m2 of beach loss at Jana Is. and 16,376 m2 of beach loss at Karan Is. There was an increase of island extent for Karan Is. from 1965 to 1968 by 9098 m2 but comparing 2017 with 1968, Karan Is. lost as much as 25,474 m2 or 2.6% of the island extent in 1968. The decrease in island aerial extent was attributed to loss of beach sand. The southern tips of the island lost the most significant amount of sand. There was also thinning of beach sand along the middle and northern sections that exposed the rock outcrops underneath the beach. The process of beach changes of both islands was tracked by the satellite imagery from Landsat 1,3,5,7 and Sentinel-2 during 1972 to 2020. Other factors including the distribution of beach slope, sea level changes, as well as wind & current from both northward and eastward components were analyzed to show its impact on the beach changes. The loss of beach sand could potentially impact the quality and availability of nesting beach for sea turtles utilizing the islands as main nesting grounds. Drivers of beach loss at the offshore islands are discussed in the context of sea level rise, dust storms, extreme wave heights and island desertification.

Analysis of Stratigraphic Subsidence Caused by Sand Leakage in Tunnel Lining

According to the phenomenon of stratigraphic subsidence caused by sand leakage in tunnel engineering, the process of sand surging was compared with the process of material discharging in the silo, the sand in the flat-bottom silo and its discharge bore and sand was used to simulate the lining structure, lining cavity and the sand in the stratum behind the lining in the tunnel engineering respectively. Through the design of indoor sand leakage experiment system, sand leakage experiment was carried out in the flat-bottom silo to discussed that under the condition of constant bore diameter, the influence of different thickness-to-span ratio on sand settlement range, settlement trough, the amount of sand leakage, and the influence of different bore size on sand leakage velocity under the condition of different bore diameter, and the critical crack ratio and flow pattern of sand were analyzed. The results showed that when the diameter of the bore was constant, the influential radius of settlement was basically linear with the thickness-to-span ratio as the soil thickness increased, and the proportion of sand loss to the total sand also increased, when the diameter of bore was different, the leakage velocity increased with the increase of the bore diameter, and the function relation could be described by the quadratic curve. There was a critical state for the collapse of sand, when the ratio of the diameter of the bore to the diameter of the sand particles did not exceed this critical state, the sand would form a stable soil arch structure above the bore, preventing the further development of sand leakage; when the collapse of sand occurred, the larger the diameter of the underground cavity, the greater the depth of the erosion, the greater impact on the ground.

Predicted Responses of Beaches, Bays, and Inner-Shelf Sand Supplies to Potential Sea Level Rise (0.5-1.0 m) in Three Small Littoral Subcells in the High-Wave-Energy Northern Oregon Coast, USA

Three small subcells (Nehalem, Tillamook, and Netarts) totaling ~55 km shoreline length in the high-wave energy northern Oregon coast are evaluated for potential beach sand loss from sea level rise (SLR) of 0.5–1.0 m during the next century. The predicted erosion is based on beach sand displacement from the narrow beaches (average ~120 m width) to increased submarine accommodation spaces in the innermost-shelf (to 30 m water depth) and in the subcell estuaries (Tillamook Bay, Netarts Bay, and Nehalem Bay), following predicted near-future SLR. Beach sand sources from local rivers, paleo-shelf deposits, and/or sea cliff retreat are discriminated by distinctive heavy-mineral tracers. Modern beach sands in the study area are derived from river sand (~75 %) and paleo-shelf sand (~25 %). The supplies of paleo-shelf sand to the beaches have largely diminished in late-Holocene time. The river-enriched beach sands have been transported offshore to the inner-shelf (0–50 m water depth) to fill increasing accommodation space in the inner-shelf during latest-Holocene conditions of relative SLR (1.0 m ka-1). To evaluate the beach sand response to future SLR, representative beach profiles (n=17) and intervening beach segment distances were compiled to yield beach sand volumes above mean lower low water (MLLW) or shallower wave-cut platforms ‘bedrock’. Across-shore cross-sectional areas, as averaged for each subcell, are as follows; Cannon Beach (304 m2), Tillamook (683 m2), and Netarts (227 m2). Littoral sand displacements to the adjacent innermost-shelf (to 30 m water depth) and the marine-dominated areas of the three estuaries are based on assumed vertical sand accretion rates of 1.0 m per century and a conservative value of 0.5 m per century. The filling of such submarine accommodation spaces will displace all active-beach sand reserves in all three subcells for either the 1.0 m or 0.5 m thickness accommodation space scenarios. Large beach sand deficits, primarily from the filling of offshore accommodation spaces, could cause further retreat of soft-shorelines, including barrier spit and beach plain/dune deposits, in the Tillamook subcell (150-280 m) and in the southern half of the Netarts subcell (370-770 m). The accommodation space approach used to predict beach sand volume loss from future SLR should have broad applicability in complex littoral systems worldwide.

Tidal sand ridges on the shelf: A numerical study of their natural morphodynamic evolution and response to interventions

Tidal sand ridges are large-scale bottom features that occur on continental shelves with strong tidal currents and abundance of sand. These ridges have longshore spacings of several kilometres, heights of tens of metres, they evolve on centennial time scales and their crests are cyclonically rotated with respect to the direction of the dominant tidal currents. The coupled Delft3D-SWAN numerical model is used to study the natural morphodynamic evolution of tidal sand ridges and their response to interventions (sand extraction and construction of islands) in a setting that resembles the Belgian shelf. New aspects in this study are that a sophisticated wave model (SWAN), a shelf with a sloping bottom and state-of-the-art formulations for sediment transport (including suspended load) are considered.Starting from an initially flat bed, model results show that sand ridges develop on the shelf that have similar characteristics as those of observed tidal sand ridges. Results further show that ridges recover after sand extraction, i.e., the original sand volume of the ridge crests is recovered on decadal time scales. Deepening of the troughs provides sand for this recovery. The recovery of the ridges is weaker when pits are located further offshore and/or are deeper. Ridges recover faster when waves are included. If a sand pit is too deep (>4 m), the ridge loses sand in the first tens of years prior to its recovery on longer time scales. This initial sand loss seems to agree with the observed loss of sand volume from a tidal sand ridge on the Belgium shelf (Kwinte Bank), which has been subject to intense extractions.Model results further show that islands lose sand on decadal time scales until they eventually disappear. This sand loss is deposited on the crests and in the troughs. The presence of islands causes the surrounding ridges to break into smaller ridges that have smaller orientation angles than those of the natural case. Using different island configurations (location, geometry and number of islands, longshore distance between islands) does not lead to qualitative changes of the model results.

Thermal Decomposition Behaviour of Foundry Sand for Cast Steel in Nitrogen and Air Atmospheres

Sand casting is the most widely used casting technique, known for ages, even since ancient times. The main goal of this study was to determine the thermal decomposition behaviour of foundry sand for cast steel. We first tested the basic properties of foundry sand, including its proximate analysis, chemical composition, and particle size characteristics; we next monitored the thermal decomposition behaviour of foundry sand for cast steel via simultaneous thermal analysis. We focused on the mass loss of foundry sand for cast steel at different heating rates in nitrogen and air atmospheres. We adopted a novel method to calculate the volatile release characteristic index of foundry sand. The volatile content of foundry sand for cast steel was very low, so the volatile release characteristic index of the sand could not be strictly calculated according to this concept. We calculated the thermal decomposition kinetics parameters of foundry sand, namely, the activation energy and preexponential factor, under kinetics theory. To thoroughly test the fitting effect, we conducted a single-factor analysis of variance on the source of error. The results showed that the independent variable has a significant influence on the dependent variable and that the fitting equation we selected is feasible and effective.

Design and Performance of Permeable Groins on a Low-Energy Natural Beach

Beach erosion, ubiquitous of sandy coasts around the world, can be exacerbated or mitigated with the use of hard engineering solutions including groins. The use of groins has been discouraged in many countries despite its capability to reduce sand losses. This study aims to design a 15 m permeable groin that allows sediment bypassing. Field experiments were conducted on a low-energy, sea-breeze dominated micro-tidal beach at the northern Yucatan peninsula during both mean and extreme wave conditions. Firstly, a short-term experiment consisted in monitoring the structure performance for 24 h during typical sea breeze conditions and the subsequent beach recovery after the structure removal. Secondly, a multi-day (60 days) experiment was conducted to investigate the performance of a single- and double-groin system during both mean and local storm conditions. Beach surveys were conducted to evaluate the beach response. Shoreline variability shows sediment accretion on the east side of the structure during sea breezes, whereas during NNW storm events, the accretion occurred on the west side. Importantly, on a scale of days, sediment bypassing occurs, and hence a net accretion was measured at both sides of the structure. During this time, a second structure was deployed 30 m apart to test the performance of a double-groin system, finding a net shoreline advance at all beach transects. Thus, low-crested short-length permeable groins are found to be a suitable emergency mitigation measure against beach erosion in micro-tidal environments causing moderate shoreline change.

Polyelectrolyte complexes based on natural macromolecules for chemical sand/soil stabilization

Soil erosion is a global problem with grave social, economic and ecological consequences. To stabilize the top soil layer, various approaches have been developed, including the use of synthetic and natural water-soluble polymers capable of binding to soil particles and forming a protective layer (crust) on the topsoil. Individual water-soluble polymers give crusts which lose mechanical stability after re-watering. We describe in the article effective stabilizers of model unstructured soil, sand, “polyelectrolyte complexes” (PECs), composed of two oppositely charged ionic polymers (polyelectrolytes), cationic poly(diallyldimethylammonium chloride) (PDADMAC) and anionic potassium humates (PH). By varying the PDADMAC-to-PH ratio, the total charge of PECs and their solubility in water was adjusted. The PECs as well as PDADMAC and PH were deposited on the surface of monomineral quartz sand, with a mean diameter of particles from 0.15 up to 2.1 mm. After drying, polymer-sand crusts were formed; their mechanical strength increased upon elevating the cationic content in the polymer formulation. Re-watering caused both polyelectrolytes and PECs with a great excess of cationic or anionic groups to be removed from the crusts, which was additionally accompanied by loss of sand and decrease in the mechanical strength of the crust. The slightly positive PECs with a significant degree of mutually neutralized charges (“hydrophobized” blocks) formed the most stable crusts due to electrostatic and hydrophobic contacts with sand particles. A correlation was thus revealed between the PEC composition and the anti-erosion resistance of the polymer-sand crusts. It is shown that the use of non-stoichiometric polycomplexes makes it possible to manipulate the mechanical strength of the resulting coatings. The described approach is promising for fabrication of polymer formulations for environmental protection, conservation/rehabilitation of landfill sites, desertification control, anti-erosion treatment of agricultural land, conservation of mining dumps, treatment of road slopes, etc.

Effect of Clay on Internal Erosion of Clay‐Sand‐Gravel Mixture

In this study, a one‐dimensional seepage test apparatus was used to investigate the effect of clay on the critical hydraulic gradient, hydraulic conductivity, migration of fine particles in soil, and percentage of fine particle loss during the internal erosion of clay‐sand‐gravel mixture, compared with clean gravel. The critical hydraulic gradient and fine sand loss percentage of the clay‐sand‐gravel mixture decreased, and critical flow velocity and the hydraulic conductivity increased. Six clay‐sand‐gravel mixture samples with different clay contents were used to evaluate the effect of different clay contents on internal erosion. As the percentage of clay mass to fine particle mass increases from 0% to 25%, the critical hydraulic gradient of soil samples decreases by nearly half and the fine sand loss percentage decreases from 13.73% to 3.48%. Overall, clay has a significant effect on the development of internal erosion of clay‐sand‐gravel mixture. And attention should be paid in engineering project; clay‐sand‐gravel mixture with a small amount of clay is more likely to be damaged than clean gravel.

Elongation and Stability of a Linear Dune

AbstractCompared to barchan dunes, the morphodynamics of linear dunes that elongate on a nonerodible bed have barely been investigated by means of laboratory experiments or numerical simulations. Using a cellular automaton model, we study the elongation of a solitary linear dune from a sand source and show that it can reach a steady state. This steady state is analyzed to understand the physical processes at work along the dune. Crest reversals together with avalanche processes control the shape of transverse sections. Dune width and height decrease almost linearly with distance downstream until the minimum size for dune is reached. This is associated with a constant sand loss along the dune, which eventually compensates for the sediment influx and sets the dune length. This sand budget is discussed to distinguish an elongating linear dune from a barchan dune and to explain the complexity of linear dune fields in nature.

Polyelectrolyte Complexes of Potassium Humates and Poly(dialyldimethylammonium chloride) for Fixing Sand Soil

The preparation of electrostatic complexes between a cationic polymer, poly(diallyldimethylammonium chloride), and natural polyanions, potassium humates, is described. The polycomplexes remain stable in the aqueous solution for a long time (up to 3 months) or form precipitates that can be easily resuspended when the sample is shaken. When aqueous solutions/suspensions of polycomplexes are applied on the sand surface, polymer-sand coatings (crusts) are formed, the mechanical strength of which increases with increasing content of poly(diallyldimethylammonium chloride) in the polycomplex. The greatest resistance to water (water resistance) is exhibited by crusts with a high proportion of mutually neutralized sections of both polymers. For such crusts, sand loss during watering is in the range from 0 to 2%. The developed multicomplex formulations can be used to stabilize soil and ground against water and wind erosion.

Myrtle Beach: A history of shore protection and beach restoration

The City of Myrtle Beach (South Carolina, USA) initiated a three-phase plan for beach restoration in the 1980s: Phase 1 — small-scale beach scraping; Phase 2 — mediumscale nourishment by trucks using inland sand; and Phase 3 — large-scale nourishment by dredge using offshore sand. Phases 1 and 2 were locally funded and served as interim measures (1981-1996) until a 50-year federal project could be constructed (1997 to present). In the course of this work, the city pioneered several approaches to beach management and became a model for the state. These include: the prototype SC beach survey program; the profile volume method for determining shorelines in the presence of seawalls, which was codified in the Beach Management Act (BMA) of 1988; the first locally funded nourishment (1986-1987) and FEMA-funded postdisaster renourishment after Hurricane Hugo 1989-1990; and the first surveys of offshore deposits for nourishment. Before restoration, nearly 65% of the 9-mile (14.5 kilometer) oceanfront was armored with seawalls, bulkheads, and revetments (1981). After nourishment, erosion control structures are now buried and fronted by a vegetated storm berm, while a wider beach accommodates millions of visitors each year. Total volumes and adjusted costs of nourishment from 1986 to early 2018 are 4,997,201 cubic yards (3,820,360 m3) and ~$70.8 million ($2018), respectively. On a unit annual beach length basis, the cost of beach restoration and improvement has averaged $46.80 per one foot of shoreline per year (~$153.50/m/yr) ($2018). Oceanfront property values on a unit length of shoreline basis presently range from ~$15,000/ft (~$49,200/m) for single-family homes to ~$75,000/ft (~$250,000/m) for high-rise buildings, suggesting that beach maintenance has cost well under 0.5% of oceanfront property values per year. Sand loss rates have averaged ~0.8 cy/ft/yr (2.0 m3/m/yr), and the rate of nourishment has been more than adequate to keep up with the ~0.37 ft (0.11 m) sea level rise between 1980 and 2018.

Willingness-to-pay for coastline protection in New South Wales: Beach preservation management and decision making

Coastal erosion is a global and pervasive phenomenon that predicates a need for a strategic approach to the future management of coastal assets (both built and natural): should we invest in protective structures such as seawalls that aim to preserve specific coastal features, or allow natural coastline retreat to preserve sandy beaches and other coastal ecosystems? Determining the most suitable management approach in a specific context requires a better understanding of the full suite of economic values the population holds for coastal assets, including non-market values. In this study, we characterise New South Wales residents' willingness to pay to maintain sandy beaches (width and length) in the face of coastal erosion along the Australian state's nearly 2200 km coastline. The measurement instrument is a stated preference referendum task administered state-wide to a sample of 2014 respondents, with the payment mechanism defined as a purpose-specific incremental levy of a fixed amount over a set period of years. We use an innovative application of a Latent Class Binary Logit model to deal with “Yea-sayers” and “Nay-sayers”, as well as revealing the latent heterogeneity among sample members. We find that 65% of the population would be willing to pay some amount of levy, dependent on the policy setting. In most cases, there is no effect of degree of beach deterioration – characterised as loss of width and/or length of sandy beaches of between 5% and 100% - on respondents' willingness to pay for a management levy. This suggests that respondents who agreed to pay a management levy were motivated to preserve sandy beaches in their current state irrespective of the severity of sand loss likely to occur as a result of coastal erosion. Willingness to pay also varies according to beach type (amongst Iconic, Main, Bay and Surf beaches) – a finding that can assist with spatial prioritisation of coastal management. Not recognizing the presence of nay-sayers in the data or recognizing them but eliminating them from the estimation will result in biased WTP results and, consequently, biased policy propositions by coastal managers.

Investigation of Coastal Environment Change Using Wave Measurement Sensors and Geographical Laser Scanner

The construction of large-scale coastal structures in any coastal area may not only have direct effects on the coastal environment in that vicinity but also cause severe property damage. In order to prevent this problem, probable effects should be appreciated before any construction and the mechanism that may cause any probable damage must be accurately analyzed along with the plans to minimize damage. This study sought to analyze the cause and mechanism of damage inflicted on coasts by artificial structures through reviewing beach erosions that have occurred on beaches on the east coast of Korea after the large-scale construction of artificial structures, for which wave heights were measured in the vicinity of those structures, and the correlation between the measurements and the analysis data of waves and coastal erosion on the surrounding beach was analyzed. In addition, the correlation between coastal erosion and wave data was applied in order to understand what impact large waves have in relation to sand loss. Accordingly, a movable-bed physical model test was employed to appraise the factors that cause coastal erosion to take place.

Morphodynamic Response to Low-Crested Detached Breakwaters on a Sea Breeze-Dominated Coast

Low-crested detached breakwaters (LCDBs) have been widely employed as a mitigation measure against beach erosion. However, only a few studies have assessed their performance in sea-breeze-dominated environments. This work investigates the beach morphodynamics behind LCDBs deployed on a micro-tidal sea-breeze-dominated beach. The study area, located in the northern Yucatán peninsula, is characterized by low-energy, high-angle waves, which drive a persistent (westward) alongshore sediment transport (O(104) m3/year). High-resolution real-time kinematics global positioning system (GPS) beach surveys were conducted over a one-year period (2017–2018) to investigate the performance of LCDBs at three sites. Moreover, unmanned aerial vehicle flights were employed to evaluate far-field shoreline stability. Field observations revealed a distinct behavior in the three study sites, dependent on the breakwaters’ transmission characteristics, geometry, stability, and shoreline orientation. Impermeable LCDBs, made of sand-filled geosystems, induced significant beach accretion (erosion) in up-(down-)drift areas. On the other hand, permeable LCDBs, made of Reef Ball™ modules, induced moderate beach changes and small erosion in down-drift areas owing to higher transmission coefficients. Measurements of LCDBs’ freeboard height show that sand-filled geosystems’ breakwaters presented a significant loss of sand during the study period, which explains the unexpected beach morphodynamic response on the lee side of the structure. Observations suggest that the study area is highly sensitive to the presence of LCDBs with low transmissivity.

Analysis of Casting Defect, Tensile Strength, and Hardness of Al-Si Casting Alloy with Percentage Variation of Clay Binder Bangkalan

Casting is one of method that used in forming the work piece by melting specific metal and pouring into moulding that has been prepared. This study aimed to determine the effect of the use of Bangkalan clay as binder in sand moulding against tensile strength, hardness, and defects in Al-Si casting alloy by using gravity casting method. The method used in this study was experimental method then using descriptive analysis. Descriptive analysis included explanation of the test result of tensile strength, hardness, and the type of surface defect of Al-Si casting. Based on the research result obtained the highest shear strength in wet condition obtained on sand moulding which had the highest tensile strength, that was sand moulding with composition of 12% Bangkalan clay, and 0.5% bentonite. While the highest hardness value of Al-Si casting result obtained on specimen with variation of 12% Bangkalan clay with the value of 131.9 HV. Casting defects that appeared on the surface of all casting product variations. The defects that found were fin defects, pinhole defects, sand loss defects, and surface roughness. Based on the result above, could be concluded that variation of 9% Bangkalan clay and 0.5% bentonite as binder was the best variation.

An analytical solution for the arching effect induced by ground loss of tunneling in sand

Because the earth pressure above tunnel crown was assumed uniform and the effect of particle flow of sand and ground loss were not considered, Terzaghi method generally produces discrepancies from model tests and field observations. To overcome this deficiency, the flow of sand particles above a tunnel was investigated firstly to define the shape and size of loosening zone by following the gravity flow principles. Then, by assuming non-uniform distribution of earth pressure and incorporating the factor of ground loss, a modified Terzaghi method has been developed. It can not only determine the loosening pressure on tunnel, but also the shape and size of loosening zone corresponding to ground loss and properties of sand particles. The research results reveal that the shape of loosening zone is ellipsoidal or a part of ellipsoid affected by the eccentricity and loosening factor of sand. The height of loosening zone increases with ground loss of tunneling, resulting in the propagation of loosening zone from deep in ground to ground surface. For most shield tunnels, with ground loss ratio less than 4.0%, the loosening zone is formed only at the upper tip of the ellipse and its shape resembles to a curved arch. According to the proposed method, the height of the loosening zone for shield tunnels in sandy ground is approximately 0.1D–0.7D (D, tunnel diameter) and the earth pressure is about 35–90% of the total overburden earth pressure for typical ground loss within the range of 0.5–4.0%. Via detailed comparison with model tests and Terzaghi method, the proposed method is proved to be closer to the model tests than the Terzaghi method. For the sake of convenience in application, simplified design curves for the height of loosening zone and earth pressure were plotted against ground loss, which is of great importance for engineers to set reasonable goal of ground loss in tunneling practice.

Factors influencing the erosivity indices of raindrops in Japanese cypress plantations

Severe soil erosion has been reported in monoculture forests without understory vegetation and litter on the floor. To clarify the factors that affect raindrop erosivity in monoculture forests, we measured raindrop erosivity in Japanese cypress (Chamaecyparis obtuse Endl.) plantations using splash cups. Splash cups can possibly measure raindrop erosivity from loss of sand (LoS). We first examined the relation between raindrop erosivity and LoS under natural rainfall in an open space. LoS was strongly correlated with raindrop erosivity factors, such as the kinetic energy and momentum multiplied by the drop diameter. We then observed LoS using 12–16 splash cups in seven plots with different canopy structures in Japanese cypress plantations. LoS at each point was compared with the amount of throughfall (Tf) and canopy structure factors, such as canopy openness (Co) and distance to the closest branch (Br). The relation between Tf and LoS was similar among the plots, except in one plot where the canopy and crown-base heights were the smallest. Our results imply that Tf is a dominant factor determining raindrop erosivity when canopy and crown-base heights are more than the threshold values (15.2 m for the canopy height and 10.5 m for the crown-base height in our forests). In plot 1, LoS was correlated with not only Tf but also Br. When analyzing all the data together using generalized linear models, LoS was affected by Br besides Tf. In monoculture forests with a high canopy, Tf measurements enable us to estimate raindrop erosivity. In monoculture forests with a low canopy, Br (or the canopy height) should also be considered when estimating the erosivity of raindrops.

A Numerical Simulation Study of the Migration Law of Water-Sand Two-Phase Flow in Broken Rock Mass

When the upper parts of coal resources are exploited, the mining overburden separated strata may easily connect with the upper unconsolidated aquifers. This may cause the water-sand two-phase fluids in the aquifers to flow underground through the falling broken rock mass. It has been found that it is difficult to eliminate sand after it has entered a mine, which tends to severely restrict the restorations of mines and causes significant economic losses. This paper studied a seepage system dynamic model of water-sand two-phase fluids in broken rock mass based on related two-phase flow theories. In addition, using FORTRAN language, it established a numerical calculation program to study the migration law of water-sand two-phase fluids flowing into broken rock mass and determined the main influencing factors on the seepage characteristic parameters of water-sand two-phase fluids in broken rock mass and the amounts of sand losses.

Improving understanding of the underlying physical process of sediment wash-off from urban road surfaces

Among the urban aquatic pollutants, the most common is sediment which also acts as a transport medium for many contaminants. Hence there is an increasing interest in being able to better predict the sediment wash–off from urban surfaces. The exponential wash-off model is the most widely used method to predict the sediment wash-off. Although a number of studies proposed various modifications to the original exponential wash-off equation, these studies mostly looked into one parameter in isolation thereby ignoring the interactions between the parameters corresponding to rainfall, catchment and sediment characteristics. Hence in this study we aim (a) to investigate the effect of rainfall intensity, surface slope and initial load on wash-off load in an integrated and systematic way and (b) to subsequently improve the exponential wash-off equation focusing on the effect of the aforementioned three parameters. A series of laboratory experiments were carried out in a full-scale setup, comprising of a rainfall simulator, a 1 m2 bituminous road surface, and a continuous wash-off measuring system. Five rainfall intensities ranging from 33 to 155 mm/h, four slopes ranging from 2 to 16% and three initial loads ranging from 50 to 200 g/m2 were selected based on values obtained from the literature. Fine sediment with a size range of 300–600 µm was used for all of the tests. Each test was carried out for one hour with at least 9 wash-off samples per test collected. Mass balance checks were carried out for all the tests as a quality control measure to make sure that there is no significant loss of sand during the tests. Results show that the washed off sediment load at any given time is proportional to initial load for a given combination of rainfall intensity and surface slope. This indicates the importance of dedicated modelling of build-up so as to subsequently predict wash-off load. It was also observed that the maximum fraction that is washed off from the surface increases with both rainfall intensity and the surface slope. This observation leads to the second part of the study where the existing wash-off model is modified by introducing a capacity factor which defines this maximum fraction. This capacity factor is derived as a function of wash-off coefficient, making use of the correlation between the maximum fraction and the wash-off rate. Values of the modified wash-off coefficient are presented for all combinations of rainfall intensities and surface slopes, which can be transferred to other urban catchments with similar conditions.

Failure Mode and Effect Analysis (FMEA) Applications to Identify Iron Sand Reject and Losses in Cement Industry : A Case Study

One of the main raw materials required in the manufacture of cement is iron sand. Data from the Procurement Department on XYZ Company shows that the number of defective iron sand (reject) fluctuates every month. Iron sand is an important raw material in the cement production process, so that the amount of iron sand reject and losses got financial and non-financial impact. This study aims to determine the most dominant activity as the cause of rejection and losses of iron sands and suggest improvements that can be made by using the approach of FMEA (Failure Mode and Effect Analysis). Data collection techniques in this study was using the method of observation, interviews, and focus group discussion (FGD) as well as the assessment of the experts to identify it. Results from this study is there are four points of the most dominant cause of the defect of iron sand (mining activities, acceptance, examination and delivery). Recommendation for overcoming these problem is presented (vendor improvement).