River Sand Mining Research Articles

RIVERS OF RAJASTHAN: A CARTOGRAPHIC PRESENTATION AND ASSESSMENT OF THEIR CONDITION

Abstract: Based on the interpretation of all the Survey of India topographical sheets of Rajasthan on 1:50,000 scale and Google Earth Images, basin wise a total of 455 rivers are identified and mapped and flow charts are prepared. Basin wise water resources development & planning documents are consulted to find out their characteristics, problems and potentials. Chambal, Mahi and Luni basins have good network of rivers. A large number of small rivers/nallah originating from low hills and uplands, are lost in sandy/alluvial plains. Overall unwarranted human activities are sole responsible for deterioration of river condition. Encroachment over river bed for agriculture and habitation is common where river passes through alluvium or sandy plain. This happened particularly in Sabi, Banganga, Shekhawati and Ruparail basins. Here large stretches of river have lost their existence. Other menace are: river sand mining; discharge of sewage and industrial effluents; dumping mining waste and slurry of marble, sandstone and granite processing units. Large scale mining activities have blocked natural drainage system and reduced free flow of rainwater in rivers. Suggestions are given to improve the river condition and increase water yield.

Effect of sea sand in the behaviour of fresh concrete partially replaced with M-sand

The research paper aims to address the environmental challenges caused by uncontrolled river sand mining in various regions of the country. Indiscriminate mining has led to multiple issues, necessitating restrictions on river sand extraction, but these restrictions have also affected the building industry's stability. As a solution, exploring cost-effective alternative materials for cement production becomes essential to promote resource utilization and efficiency in the construction sector. The study focuses on using excavated marine sand as a fine aggregate to develop enduring and resilient concrete. Partial replacement of river sand and manufactured sand (MS) with dredged sea sand (DSS) is conducted to understand the benefits of the proposed concrete in terms of strength and durability compared to traditional concrete made of river sand (RS). This investigation is significant in the current scenario to assess the potential of DSS as a building material. The methodology employed includes grading analysis, assessment of flexural and compressive strength, evaluation of water absorption, alkalinity testing, rapid chloride penetration test, bond strength examination, and sorptivity assessment. The research aims to determine the behavior of fresh concrete with sea sand as a partial replacement for traditional sands, ultimately contributing to more eco-friendly and resource-efficient construction practices. The gradation has been done in three different proportions say 10, 20, and 30%. The results indicate that for all the mixes the compressive strength of the cylinder shows an average value of 0.83 times the strength of the cubes, while the flexural strength value (K√fck) shows an average of 0.69 times the strength of the cubes for all the mixes. RCPT and Water Absorption results show an average value of 1775 and 3.96 respectively which is within the limit specified. The addition of MS improves the alkalinity of concrete and the result was in accordance with ASTM D 4262. The bond strength increases with an increase in the replacement of sea sand and sorptivity decreases with an increase in the replacement of sea sand. This is indeed a study of the strength of concrete and toughness using MS as a partial replacement for dredged sand. The analysis shows that a 30% replacement of dredged sea sand with MS does not impact the overall strength of concrete, ensuring satisfactory strength and durability.

Impact of upstream reservoirs on geomorphic evolution in the middle and lower reaches of the Yangtze River

AbstractIntensive human activities in river basins have substantial effects on fluvial hydrological and morphological processes and developmental trends. In this study, we assessed the evolutionary characteristics and developmental trends of the fluvial morphological system of the Three Gorges Dam (TGD) downstream to understand the impacts of human activities on the fluvial hydrological–morphological system of the region. The results indicated that the Three Gorges Project (TGP) and other upstream cascade reservoirs promoted sediment retention, which in turn aggravated the trend of declining sediment load and cumulative scouring over a long distance in the channels downstream of the TGD. Approximately 84% of scouring occurred in the low‐water channels, along with thalweg scouring and riverbank collapse. Notably, extended operation of the TGP and other upstream cascade reservoirs has resulted in gradual changes in the downstream riverbeds. Specifically, we found that the most intensive scouring zone shifted downstream from the near‐dam Yichang–Chenglingji reach (0–408 km) to the Chenglingji–Hankou reach. The scouring–silting distribution in swales has also changed: the scouring of deep swales and silting on floodplains prior to the TGP have been replaced by the scouring of both deep swales and floodplains. The scouring intensity of riverbeds in the Yichang–Hukou reach (954 km) was slightly higher than that forecasted prior to the TGP; the scouring intensities increased significantly during 2013–2021, which could be attributed to the TGP and other upstream cascade reservoirs; river sand mining and waterway dredging are secondary factors. We conclude that, owing to the effects of sediment retention by cascade reservoirs in the upper reaches of the Yangtze River (or Changjiang River), the cumulative scouring intensities of riverbeds in the middle and lower reaches of the Yangtze River will continue to increase in future decades.

The impact of river sand mining on remobilization of lead and cadmium in sediments – A case study of the Jialing River

Due to the fast pace of urbanization worldwide, industrial sand mining activities have imposed great pressure on the environment, and consequently, these activities have led to serious environmental problems in aquatic ecosystems. However, the current understanding of the effect of sand mining on heavy metal remobilization in river sediments remains incomplete. The present study employed sediment quality guidelines (SQGs) and the sequential extraction (SE) and diffusive gradients in thin films (DGT) techniques to comprehensively investigate the effect of sand mining on the remobilization process of heavy metals in the aquatic system of the Jialing River. The SQGs results indicated that stations (S1 to S4) with sand mining disturbance exhibited Pb and Cd accumulation in surface sediments. Both Ctotal-Pb (61.78–122.04 mg·kg−1) and Ctotal-Cd (0.85–3.96 mg·kg−1) were higher than CSQGI (60 mg·kg−1 for Pb and 0.5 mg·kg−1 for Cd) and TEC (35.8 mg·kg−1 for Pb and 0.99 mg·kg−1 for Cd) limitation in most of sand mining stations. Pb and Cd were mainly bounded in the acid-soluble/exchangeable fraction (F1) and oxidizable fraction (F3) of the surface sediments. At the four stations with sand mining disturbance, about 5–10 folds of DGT-labile Pb and Cd were released in deep sediments (−9 to −12 cm), and Pb and Cd exhibited a transport trend from the sediments into the overlying water, while the above phenomenon was not observed at the two stations without sand mining activities. Correlation analysis revealed that DGT-labile Pb and Cd were suitably correlated with the F1 and F3 fractions, indicating that the acid-soluble/exchangeable and oxidizable fractions were the main sources leading to Pb and Cd remobilization in the sediments. A potential mechanism explanation may be that (1) intense sediment stirring could result in remobilization of the weakly bound fraction, which is related to the contribution of the F1 fraction, and (2) Cd/Pb experienced a corelease process with sulfur due to O2 introduction (elevation of the dissolved oxygen level) attributed to sediment evacuation, which is related to the contribution of the F3 fraction. The above results suggested that sand mining in the Jialing River should be paid high attention to prevent heavy metal pollution in aquatic ecosystem.

Assessment of Opinion and Awareness of the Construction Industry on Suitability of M Sand as a Replacement to River Sand

Fine aggregates are an essential raw material required for concrete production. Majority of the fine aggregate demand is supplied through natural river sand. However, river sand mining is not sustainable in the long run and impacts the environment severely. A more sustainable and cost-effective replacement to river sand should be adopted quickly. Manufactured sand or M sand is a promising alternative to river sand. The suitability of M sand as a replacement to river sand and the opinions and perspective of the construction industry were assessed by doing a comprehensive literature review and collecting data from industry professionals through a questionnaire. The questionnaire was assessed under their categories such as performance, economy, environmental and general. Respondents were also asked to grade their presumed knowledge on each category being assessed, in order to evaluate the validity of individual opinions. The results indicated that the opinion of construction industry professional’s regarding M sand on economic and environmental aspects are similar to the findings of the literature. However, the professionals opinions regarding performance aspects of M sand was mostly mixed and contradicts with literature findings. Professionals who rated their knowledge highest had different opinions about M sand indicating the presence of severe misconceptions and inadequate knowledge within the industry. To overcome this, industry professional’s knowledge on M sand should be raised by providing accurate information about M sand and its benefits. Furthermore, the industry professional’s opinions acknowledged that M sand is being currently underused within the industry. They were confident that in future, M sand use would increase drastically.

The environmental impacts of river sand mining.

The demand for construction-grade sand is growing at a tremendous rate and the world is expected to run out of this resource by 2050. Construction-grade sand, hereafter referred to as 'sand', can be found in (former) aquatic environments, such as rivers and is a provisioning ecosystem service. Even under controlled circumstances, the practice of extracting the sand from the riverbed and -banks impacts the environment. Unfortunately, many countries lack sand mining regulation policies and in combination with a high demand, this results in indiscriminate and illegal mining. To create effective policies for sustainable extraction of river sand, there is a need for both qualitative and quantitative data on the effects of river sand mining. This paper brings together the effects of river sand mining on the physical, biological, chemical, and anthropogenic environment through a systematic literature review. The effects found are widespread and often cumulative. In the physical environment, the primary effects are riverbed widening and lowering. In the biological environment, the overarching effect is a reduced biodiversity and stretches from the aquatic and shoreline flora and fauna to the whole floodplain area. The effects on the chemical environment are a reduced water, air and soil quality through pollution. The effects on the anthropogenic environment comprise of damaged infrastructure, bad working circumstances for workers, limited access to water and agricultural losses. The findings of this research emphasize the complexity and cascading nature of the effects of river sand mining, as well as the severity and urgency of the problem. Based on the effects found and the four environments, a set of guidelines are proposed at the end of this paper to be used for global agenda making regarding sustainable sand extraction. Future research should prioritise quantifying the observed effects and developing science-based policies for sustainable mining.

Investigating Shoreline Migration due to Sand Mining in Some Communities of Yenagoa Local Government Area using GIS and Remote Sensing

This study investigates the impact of sand mining activities on some host communities within Yenagoa. The mining activities are considered to include the whole chain, from the dredging (mechanical or manual) to the end user (reclamation, filling, or construction). Impacts are assessed under categories ranging from environmental to infrastructural and ground damage. The methods of study include physical onsite observations and quick field assessments of soil type in areas directly connected with the river sand mining activities, and use of GIS and remote sensing techniques. Results show a direct link between the sand mining activities and damages to infrastructure, the natural environment, and shoreline migration. There is a steady increase in bare-land (i.e., land cover removal) and river expansion with increasing mining sites and dumpsites from 1990 to 2021.

Human impacts on riverbed morphology and hydrology in the lower reaches of the West River, China

AbstractNatural and anthropogenic factors have led to a series of fluvial sedimentation and hydrological changes in the lower West River, China. To evaluate the influence of human activities on the channel's morphology and examine the hydrological responses, we analyzed channel adjustments and changes of low water levels in the main river channel between Wuzhou and Zhaoqing that occurred over the recent decades. Due to a remarkable decrease in the suspended sediment concentration, the suspended sediment outputs during this period were larger than the sediment inputs for 27 consecutive years from 1987 to 2013. Therefore, the riverbed became a sediment source, with a high scouring of riverbed material. Between 2004 and 2014, the channel capacity of the lower reaches increased by 302.02 × 106 m3, and the average riverbed elevation decreased by 2.21 m, approximately 11.8% of which was caused by bed sediment loss induced by natural scour through sediment depletion; the remainder was caused by waterway engineering and sand mining, accounting for 0.8 and 87.4%, respectively. Approximately 91.3% of 1,312 river cross‐sections exhibited downcutting, indicating significant adjustment of the riverbed. This resulted in a substantial decline in the low water level in the 44‐km upstream section above Ducheng, which is located at the end of the tidal limit during dry seasons. However, this change was not noticeable in the section below Ducheng owing to the small water surface gradient and tidal influence. These findings reveal that human activities are a major driving force in the evolution of large rivers and the complexity of the hydrological responses to riverbed downcutting in a tidal reach, providing useful information for future river sand mining management and navigable engineering design of the lower West River and other rivers.

ASSESSMENT OF SEDIMENT REPLENISHMENT VOLUME IN LANGAT RIVER SYSTEM

The river sand mining activity has taken place in a sand-bed river system in Selangor, Malaysia for decades even before the legalisation was initiated in 2008. This study focuses on the determination of optimum sand extraction for low-flow and high-flow seasons. The sand replenishment rate was used as the benchmark in determining the threshold level of the extractable rate in the Langat River, Selangor system. The total sediment load was computed using Yang (1973) equation due to the high percentage of agreement between the predicted sediment load and measured sediment load. Almost 41.6% of the predicted data fall within the allowable discrepancy ratio test between the predicted value and measured value. The comparison of sand replenishment rate in high and low flow seasons proved that the river system has quicker capabilities in sand replenishment rate at the extraction point during the high-flow season compared to the latter by 83%. The quantifiable volume of the extractable sand rate is proposed specifically during low-flow months (May to September) whereby the slower replenishment rate is critical and riskier. The optimal sand mining volume during the low-flow months is calculated by reducing 10% from the total replenishment volume and the recommended optimum extraction load has been delivered by the number of 25 tons lorries for easier observation by the contractor and authority’s body. The monthly optimum extraction in Langat River during low-flow months is calculated at a minimum of 437 trucks to a maximum of 20,114 trucks per month.

Effect of Coal Bottom Ash as Partial Sand Replacement for Lightweight Aggregate Concrete

Environmental degradation due to disposal of waste namely coal bottom ash waste from thermal power plant, clinker waste of palm oil mill and river sand mining activity for concrete production need to be resolved. Palm oil clinker lightweight concrete with zero granite aggregate that been produced in effort to reduce dependency of natural stone consumption has been further explored its potential in this research. Thus, the present research investigates the compressive strength, water absorption and acid resistance of lightweight aggregate concrete containing coal bottom ash as partial sand replacement. Five types of concrete mixes were produced using 0%, 10%, 20%, 30% and 40% coal bottom ash as fine aggregate replacement. After curing process, specimens were immersed in acid hydrochloric solution before subjected to compressive strength testing. Findings show that all specimen experience strength reduction after exposed to acidic environment. On overall, the use of coal bottom ash influences the durability performance of lightweight aggregate concrete.

Investigation on joint mining of Rare earth elements and zircons from the Yangtze River, China

Rare earth elements(REEs) have attracted much attention in recent years. China is the leading supplier of REEs, thanks to its vast mineral reserves and technological innovation since the 1960s. In the same period, China’s sand used in construction has also increased year by year. The integrated application of the full utilization of sand for construction and exploration and mining engineering of REEs have been the subject of many recent studies. This paper compares the main erosion areas of the Changjiang River. And the abundance of zircon, a byproduct of heavy rare earth elements in different regions. Yichang station is considered as a possible mining site. According to the characteristics of mechanical separation process and hydrometallurgy, a comprehensive system of river sand mining and REEs extraction was designed. This system is well established in zircon mining(LCA). However, the REEs extraction of river sand is affected by mineral composition, which requires a large number of experiments to optimize the process. This area needs further research.

Assessment of government supervision on the loss of sea sand resource in China

Illegal mining activities on offshore sands have recently increased dramatically in China owing to the strong demand of the construction industry and restriction of river sand mining. By studying the loss mechanism of marine sand resources, this study proposes a simplified linear programming model to quantitatively analyse the control effects related to resource loss and law enforcement costs. To accurately simulate the effectiveness of law enforcement activity, a set of variables is designed in the model to describe the severity of illegal mining and enforcement skills of the officers. Subsequently, based on different settings of law enforcement capability, the model can not only make reasonable projections for sand losses but also provide a minimum cost solution for marine sand control for government agencies. Finally, various regulatory measurements and suggestions are discussed to improve the effectiveness of the government’s regularisation and cost optimisation for law enforcement.

Reply to comment on, “Sediment budget and morphological change in the Red River Delta under increasing human interferences” by N.D. Ve, D. Fan, B.V. Vuong and T.D. Lan [Marine Geology 431 (2021), 106,379

Anh (2021) asserts that the sediment budget model by Ve et al. (2021) of the subaqueous Red River Delta (RRD) is inaccurate because of some fundamental flaws in the DEM analysis and budget estimation. In fact, bathymetric data from the two earliest charts have been validated with data from a survey carried out over a short time span (1927–1930) and a linear semi-variogram model used to do the kriging interpolation. Different grid cell sizes have a negligible effect on the DEM analysis, and the effect of relative sea-level rise has been ruled out by normalization of bathymetrical data from sequential charts to a common tidal datum. Furthermore, the estimation of the amount of deposited sediment on tidal flats is correct, although a typo of sediment volume unfortunately yielded a wrong value. We can thus confirm that the data in the sediment budget model of Ve et al. (2021) are reliable.The sediment budget model can be improved by full consideration of sediment from source to sink processes as suggested by Anh (2021). We therefore refine the model by considering river bedload and sand mining in the RRD in the sediment input item, and separate the subtidal RRD into three subzones to calculate their average depositional/erosional sediment volume and mass. In the revisited model, a total of 54.7 Mt./yr is inferred to be deposited in the subaqueous RRD from the intertidal flats to the delta-front slope, of which 75.3% and 24.7% are conceivably sourced by the Red River and eroded from the prodelta and offshore shelf, respectively. However, the controlling mechanism of secular erosion at the prodelta and offshore shelf is so far not well known, and this will need to be investigated in the future.

CONSTRUCTION AND DEMOLITION WASTE MANAGEMENT LEGISLATION AND FRAMEWORK IN INDIA - A MINI REVIEW WITH BEST PRACTICES IN C & D WASTE MANAGEMENT

The construction industry in Indian cities has grown rapidly in recent decades due to population growth, industrialization and the introduction of new infrastructure projects, which has led to a tremendous growth in the construction industry.A key demand as a result of the growth of the Indian construction sector is expected to be the supply gap in terms of construction materials such as sand, limestone, and aggregate. The Supreme Court has had a major impact on the construction industry due to the ban on river sand and stone mining. It is designed to find an alternative source of natural raw materials.An alternative source in the field of aggregate construction recycled by C&D Waste could replace a significant amount of natural aggregates that run abroad in countries such as the United States, France, Denmark, Germany and Japan. Has been While various methods of waste have been suggested in the literature, the quantification of waste produced in India is insufficient.This inadequacy is due to lack of proper classification control procedures, lack of joint C&D waste estimation procedures, and knowledge of C&D waste processing among generators, collectors, operators, regulators, and the general public. The C&D Waste Management Rules 2016 to address the responsibilities of all stakeholders for the systematic collection, storage, transport, treatment / processing, and disposal of C&D bins in India was introduced. This comprehensive study seeks to analyze current legislation and challenges, and proposes an informational framework for systematic collection, storage, treatment / processing, and C&D waste disposal.This article examines the current methods of C&D waste in India. It also studies the institutional, regulatory and legislative framework in India in the field of construction and demolition waste management.

A DPSIR Assessment on Ecosystem Services Challenges in the Mekong Delta, Vietnam: Coping with the Impacts of Sand Mining

River sand mining has been a concerning problem for the southern Asian developing nations. The rampant growth of urbanisation in developing countries has led to an extensive need for and consumption of sand. The Mekong River and its delta are an essential part of southern Vietnam, and also a global biodiversity hub that is currently being exhausted by intensive sand mining. The understanding of the cause–effect of the sand mining over the Mekong delta region and river, from a systems-thinking perspective, is lacking, not only with Vietnam but also with other countries along the Mekong River. The DPSIR framework (Driver–Pressure–State–Impact–Response) is a useful tool to assess and describe the cause–effect within an ecosystem to aid in a better systems-thinking approach for stakeholders, policy makers, and governance managers to draft response measures. This study used the DPSIR framework to assess the different effects of sand mining on the ecosystem services and human well-being in the Mekong River and delta region of Vietnam. Rapid population growth, urbanisation, and infrastructure development needs remain as primary drivers for the sand consumption. The DPSIR study showed a holistic view of several interlinked pressures and state changes in Vietnam’s Mekong, along with some potential responses, to form systematic, sustainable approaches for mitigating and adapting the impacts caused by extensive river sand mining.

Predicting the Toxicities of Ternary Mixtures of two Metals and Sodium Dodecyl Sulfate to Serratia marcescens (SerEW01) from Otamiri River Water

Background: Otamiri river server as a source of water for domestic activities, urban farming, recreation, aquatic foods in Owerri and environs. It also receives untreated domestic, industrial and agricultural waste water and run offs from the municipality. Seepages from solid wastes dumps at the river banks and sand mining activity going on in the river could also constitute environmental hazards
 Aims: This study aims at evaluating the interactive effects of the ternary mixtures of sodium dodecyl sulfate (SDS) and some divalent metals on preponderant bacterium (Serratia marcescens (SerEW01)) from the river.
 Study Design: Fixed ratio ray design was used for the study, with inhibition of dehydrogenase activity as end point.
 Place and Duration of Study: Owerri, Imo State, Nigeria, June – December, 2019.
 Methodology: The bacterium was earlier isolated as the preponderant bacterium isolate from the river water. Fixed ratio ternary mixtures (Equieffect concentration (EEC50) and arbitrary concentration (ABCR) ratios), SDS + Pb + Zn, SDS + Cd +Zn, SDS + Pb +Ni, SDS + Ni + Cd, SDS + Co + Pb and SDS + Co + Cd were designed to evaluate the combined toxicities of these toxicants. Toxicities predicted by concentration addition (CA) and independent action (IA) models were compared with the experimentally observed toxicities.
 Results: The EC50S observed ranged from 0.046 ± 0.003 mM (Zn) to 2.329 ± 0.092 mM (SDS). The EC50S of the toxicants were statistically different from each other (P<0.05). The order of increasing toxicities were SDS >Pb >Ni > Co > Cd(II) >Zn. Concentration-dependent toxicities with progressive inhibition of the dehydrogenase activity as the concentration increased were observed.. In all ternary mixtures, both the experimentally derived, CA and IA-predicted EC50S were statistically different from each other. Both models predicted lower toxicities compared to the experimental data. The Toxic Index and Model Deviation Ratio indicated synergistic interaction of SDS and metal ions against S. marcescens (SerEW01)
 Conclusion: This study could constitute base line information towards assessing the possible environmental hazards associated with co-contamination of the environment by SDS and divalent heavy metals, more so when both pollutants are common aquatic pollutants.

Economic and environmental impacts of sand mining activities at sadang river Pinrang Regency, South Sulawesi

Sand is a material needed for various purposes such as construction materials and backfill materials so that the need for sand continues to increase. The economic potential in the form of generating income for both workers and companies has triggered increased sand mining activities in the Sadang River in Pinrang Regency. The research took place between September and November 2019 which aimed to determine the economic potential and encironmental impact of the Sadang River sand mining in Pinrang Regency. The research area covers three districts included in the Sadang River sand mining area of Pinrang Regency namely Patampanua, Duampanua and Cempa Districts. A field survey was conducted to find out the amount of production volume, production costs, mining and transportation activities. The results showed that the Sadang River sand mining has considerable economic potential. In addition to direct economic benefits, it also provides indirect economic benefits for the community around the mining area. If the river sand mining has been deemed damaging to the environment and disrupting the function of the river, then the activities at Sadang River shows the opposite, namely that the Sadang River sand mining can help restore the hydrological function of the Sadang River to prevent siltation of the Sadang River due to sedimentation so as not to cause overflow and floods that can damage residents’ settlements and agricultural land in three districts.

Impact of sand mining on the changes of morphological and physical dynamics in Sa’dang River, Pinrang District, Indonesia

The research aimed to investigate the morphological changes and physical dynamics conditions of the Sa’dang River associated with river sand mining activities. The research is expected to benefit the efforts of the management of sand mining in this area and enrich knowledge about the issues of river sand mining. The study was conducted in Sa’dang River sand mining area, which includes villages of Pincara, Massewwae and Mangki of Pinrang District in South Sulawesi Province, Indonesia. A field survey was conducted in October to December 2019 to see the condition of the river along with the mining activities that were taking place. Field data analysis was combined with google earth imagery data for 2006, 2014, 2017 and 2019 using ArcGIS 10.5 software to see changes in river morphology, formation and extent of point bar and channel bar, as well as changes in the area of river water bodies and non-water river bodies. The results showed that the changes in morphology and physical dynamics conditions of the Sa’dang River showed their own pattern. If sediment deposits forming point bars or channel bars were reduced, the area of river water bodies tended to increase. Or in other words, the width of the river is inversely proportional to the increase in the area of the river water body if the area of sediment deposits that form the point bar and channel bar tends to decrease.

Evaluation of infilling and replenishment of river sand mining pits

Rivers are one of the main sources to supply sand and gravel for construction projects. Depending on river morphology and hydraulic characteristics, its sediment transport capacity, and mining operation method, the extraction of river bed materials may affect its ecosystem through bank and bed erosion. To advance the mechanisms of river pit infilling, the effects of various parameters (i.e., the distance between pits, the pit plan shape, the pit depth, sediment size, and approaching flow velocity) on pit infilling volume are investigated in this research. The results of this research show that infilling volume of upstream pit is insignificantly affected by the distance between the pits, and it is completely refilled for different distances. However, the infilling volume of downstream pit decreases by increasing the distance between the pits. In addition, by reducing the ratio of pit length to its width (pit shape extension in spanwise direction), the pits can be excavated in a shorter distance from each other; when this ratio decreases by 15%, the infilling volume increases up to 30%. Subsequently, as a cost-effective option, the pit distance can be reduced up to 50% in these conditions. According to the obtained results, although the sediment size has negligible effect on infilling volume in the studied range, the infilling volume increases up to 20% by an increase of 8% in the approaching flow velocity. Increasing the ratio of pit length to its width (pit shape extension in streamwise direction) highlights the effectiveness of smaller depths, so that the infilling volume increases up to 20% by a decrease of 20% in the pit depth. In this regard, it is recommended that the pit depth be restricted to 70% of the channel flow depth to have a complete pit refilling.

Meriç Nehri Yatak İçi Kum Alımının Jeomorfolojik Değerlendirmesi

In-channel sand excavation has been implemented on the River Meriç flowing through Turkey for the last 15 years to prevent or mitigate floods and to generate income. Sand removal was carried out by digging in-riverbed sand deposits in the 12 km section of the river running alongside the city of Edirne. This study aimed to investigate the geomorphological effects of in-channel sand excavation on the River Meriç in the Edirne province and to evaluate the results. The 12 km section of the River Meriç in the Edirne province was examined between 2008 and 2019. The braided channel pattern of this part of the river was mapped for a one-year period. Annual variation characteristics were determined using GIS and RS. Flow observations and change characteristics in the river channel morphology were then correlated. Changing the natural river channel form and channel cross-sectional characteristics of the river has led to changes in river erosion and deposition. It is predicted that these changes will play a triggering role in causing unexpected fluvial geomorphology problems. We suggest that the expected economic input for river sand mining should be re-evaluated from the perspective of cost-benefit analysis.