Instream Mining Research Articles

Vertical riverbed deformations due to in-stream mining

Comparison of the longitudinal profile of a number of lowland rivers in Russia, revealed their deformation due to a half-century of sediment flux and channel morphology adjustment. This problem remains relevant both in theoretical and practical aspects, especially for rivers where long-term mining of sediments from the stream beds extends from kilometers to tens of kilometers. The removal of a large amount of alluvial material from the sediments transport and changes of the riverbed morphometric characteristics triggered the process of leveling the sediment transport capacity along the river by the scour and resulted in a lowering of the bottom and water surface. The intensity of the incision reached 3–8 centimeters, and its progradation along the river 400–700 meters per year. Retrogressive erosion is pronounced, while progressive one is less pronounced, because partially replaced by mechanical removal of alluvial material. Over the past decades the shape of the longitudinal profiles changed from convex or straight to concave with no signs of recovery, despite the mining has been quite moderate for last 30 years or completed on the explored rivers.

Higher-order turbulence statistics and multiscale characterization of morphodynamics in a riverbank section with an upstream mining pit

Channel dredging has become a common phenomenon across several fluvial systems. Pits dredged in the riverbank can influence the downstream turbulence and affect the bank slope and central channel morphodynamics. Erodible bed experiments were conducted in a laboratory flume having a riverbank cross section with three different bank slopes, i.e., 25°, 31°, and 40° with and without a mining pit. Flow over the bank slope and near the bank toe was most affected by the pit excavation at the channel upstream. Turbulence levels were amplified within the flow over the slope and near the bank toe. The logarithmic scaling range of higher-order fluctuations at the bank toe is greater for with pit case. The complex interaction of simultaneous processes like pit migration, sliding failure and bank erosion, and fluvial erosion was studied at multiple length scales and time scales. A wavelet cross correlation analysis was used to calculate the celerity of bedform migration at the bank toe along the flow. Statistical celerity of bedforms with smaller scales (up to 15 mm length scales) is significantly higher due to pit interaction. The study reveals that instream mining has notable effects on the inherent nature of higher-order turbulence statistics, especially near the bank slope and toe, as well as the multiscale morphological structures.

In-stream Mining in Alluvial River Channels: Response, Consequences and Perspectives

Abstract—On the basis of long-term field and analytical research, the response of the channels of different rivers to one of the types of mechanical impact on rivers – the in-stream mining – is considered. The nature and rates of the response of the river channels of free-flowing and regulated rivers to the in-stream mining, disturbance extent of the channel morphology and the rivers hydrological regime are revealed. The purpose of the work is to assess the possibilities of in-stream mining and allowable mine’s sizes which bases on the general principles of the theory of fluvial processes, and to minimize the negative effects of given mechanical disturbances on rivers and floodplains

A policy approach for sustainable governance of sand mining activities in NW Kashmir Himalayas

Sustainability in river bed mining is emerging as a sensible yet unexplored area of research. This study assessed the socio-economic and environmental implications of mining operations in the River Jhelum of North-Western Kashmir Himalaya. To achieve the objectives of the study, surveys, focal group discussions, and questionnaires were used. Further, the high-resolution Google Earth imagery was used to monitor the distribution of mining boats correlated with extensive field-based surveys along a stretch of 150 km of Jhelum River. Manual counting from satellite data depicted that 2976 mining boats are currently operating in river Jhelum from the stretch between Khanabal to Boniyar involving manpower of about 17856 persons. The results indicated that ∼2273662.74 metric tonnes of sand are extracted from river Jhelum annually. Socio-economic analysis revealed that sand mining serves as a source of livelihood to ∼20000 families. Surveys and visual observations at mining sites revealed that the rampant riparian zone and mushrooming of in-stream mining activities have impacted river health causing erosion of river banks, flood plains, and pollution of the river ecosystem. This study offers a policy approach for sustainable governance of sand mining activities that pledge environmental protection with minimum regulatory costs and high levels of public cooperation.

On the Morphodynamic Alterations around Bridge Piers under the Influence of Instream Mining

Sand mining in an active alluvial channel can compromise the streambed stability of the hydraulic structures nearby. This experimental study is aimed at investigating the effects of rectangular mining pit on the morphodynamics around circular tandem piers in a movable bed. A rectangular pit is excavated upstream of two circular piers embedded in the sand-bed in a tandem arrangement. The results are then compared to a case having only the piers without any mining pit. Turbulent stresses and mean velocities in the near-bed region rise significantly at the upstream region of the piers in the presence of a pit. Also, stronger flow reversal and horseshoe vortices have been detected at the base of the pier front. Due to these alterations in the nature of turbulence, erosion of channel beds upstream of the piers, increased scour depths, scour volume, and lateral erosion of the scour hole have been observed. Dynamic evolution of the local scour at various time scales has been studied using a wavelet cross-correlation method. Spatial evolution of local scour is found to be faster when a pit is excavated in the channel. Thus, mining activities near the piers can lead to significant changes in the flow-field, causing excessive scour around piers.

Effect of instream sand mining on hydraulic variables of bedload transport and channel planform: an alluvial stream in South Bengal basin, India

Sand mining adversely behaves with changing river system, especially in the bedload transport process. This study aims to find out the relationships between river water flows, sediment transport regime in bedload transport and also tries to determine how instream mining affect the sediment inflow and channel planform change. The field study has been conducted in three selected sites on Kangsabati River situated in the lower, middle and upper course. Several established equations were applied to derive the results from water flow and sediment regime. GSTAT was used to prepare coarse medium (CM) diagrams and tractive current deposits to analyze the trend of sediment throughout the river course. Sediment and bedload transport were measured using Ackers and White (J Hydraul Eng Div ASCE 99(hy11):2041–2060, 1973) and Meyer-Peter–Muller methods (IAHSR 2nd meeting, Stockholm, appendix 2. IAHR, 1948). Shear stress and critical shear stress were computed using Shields (Application of similarity principles and turbulence research to bedload movement, 1936) and DuBoys equations whereas Friend and Sinha’s method (Braiding and meandering parameters, vol 75, No 1, Geological Society, London, 1993) was used to detect irregular planform response caused by sand mining. Regression analysis denotes that mining intensity can be change the shear stress (R2 = 0.972); velocity (R2 = 0.683); grain diameter (R2 = 0.555) and sediment concentration (R2 = 0.997) on bedload transport. Mining activities can be changes of hydraulic responses as well as interruption of sediment and bedload transport throughout the channel. In context of sand mining, planform response denotes that thalweg shifting leads to massive sandchar deposition in upper course, huge channel incision causes river bank erosion in middle course and pool–riffle alteration expanded in channel and pit area in lower course.

Mining pit migration of an alluvial channel: experimental and numerical investigations

ABSTRACT Sand mining changes river morphology, which alternatively has adverse impact on hydrology, environment, and ecology of the river system. Quantitative analysis of migration speed of pit and erosion in the mining zone is necessary for both sustainable mining operation and channel bed stability. Sediment transport mechanism in a river also gets affected due to in-stream mining activities. In this research a numerical model has been developed to estimate migration of mining pit by using flux vector splitting finite difference scheme. One-dimensional shallow water hydrodynamic equations and sediment mass conservation equation of bed material for equilibrium bed load sediment transport have been used for simulation of channel bed profile. Here, the applicability of various bed load transport formulation on pit migration has been studied. The use of different bed load transport formulation shows different migration speed of mining pit and downstream erosion. The model is verified by using laboratory flume experiment data for mining pit migration of rectangular and trapezoidal pit. High-resolution experimental data of bed profile obtained from ultrasonic ranging system shows migration and downstream erosion of mining pit. Numerical model developed in this study manifests good agreement with the characteristics of propagation of mining-induced erosion for different bed load transport formulation, while quantitative agreement is achieved only for the Van Rijn approach of bed load transport equation as a closure of the governing equations. The present experimental and numerical analysis shows that channel morphology due to mining can be predicted by using one dimensional numerical model within the acceptable limit.

Variation in flow and suspended sediment transport in a montane river affected by hydropeaking and instream mining

The temporal and spatial variability of water and sediment loads of rivers is controlled by a suite of factors whose individual effects are often difficult to disentangle. While land use changes and localised human activities such as instream mining and hydropeaking alter water and sediment transfer, tributaries naturally contribute to discharge and sediment load of mainstem rivers, and so may help compensate upstream anthropogenic factors. The work presented here aimed to assess water and the sediment transfer in a river reach affected by gravel extraction and hydropeaking, set against a backdrop of changes to the supply of water and sediment from tributaries. Discharge and suspended sediment transport were monitored during two average hydrological years at three cross-sections along a 10-km reach of the upper River Cinca, in the Southern Pyrenees. Water and sediment loads differed substantially between the reaches. The upper reach showed a largely torrential discharge regime, controlled mainly by floods, and had high but variable water and sediment loads. The middle reach was influenced markedly by hydropeaking and tributary inflows, which increased its annual water yield four-fold. Suspended sediment load in this reach increased by only 25% compared to upstream, indicating that dilution predominated. In the lowermost section, while discharge remained largely unaltered, sediment load increased appreciably as a result of changes to sediment availability from instream mining and inputs from tributaries. At the reach scale, snowmelt and summer and autumn thunderstorms were responsible for most of the water yield, while flood flows determined the magnitude and transport of the sediment load. The study highlights that a combination of natural and human factors control the spatial and temporal transfer of water and sediment in river channels and that, depending on their geographic location and effect-size, can result in marked variability even over short downstream distances.

The Role of Human Activities in Streambank Stability: Lower Sakarya River (NW Turkey)

The main objective of this study is to determine historic and current human impacts on streambank stability in Lower Sakarya River. Remote sensing and Geographical Information System techniques with conjunction field works were performed to identify the impact of human alteration on streambank stability in the riverine environment of the eastern portion of Sakarya province. LULC (land use/cover) and historical streambank changes were analyzed from Landsat 1-5 Multispectral Scanner (MSS), Landsat-7 Enhanced Thematic Mapper Plus (ETM+), and Google Earth images between 1995 and 2016. As results, a significant LULC changes have been observed along the buffered zone due to population growth. Recently, change in LULC type from agricultural to urban usage has changed river equilibrium. The stream channel also became more stable and straight as man-made modifications including a hydropower (HES) dam constructed in 2010, which primarily reduced flood frequency, water velocity, stream power, shear stress on sediment particles temporarily deposited along the streambank. After the year of 2010, downstream portion of the dam had experienced narrowing and expanding mid-channel bars. Moreover, the channel has been slightly moved towards east especially along urbanized and sinuous courses. The streambank displacement ranged from 2.9 m to 36 m in the region. Instream mining activities and bridge constructions in the region also disturb active streambanks, which raise a concern about instability of streambank and potential damage to infrastructures. Such studies are extremely important for understanding basic mechanisms of streambank evolution for further river restoration practices.

Channel dynamics and geomorphic resilience in an ephemeral Mediterranean river affected by gravel mining

Gravel mining has been a widespread activity in ephemeral rivers worldwide whose long-lasting hydrogeomorphological impacts preclude effective implementation of water and environmental policies. This paper presents a GIS-based method for temporal assessment of morphosedimentary changes in relation to in-channel gravel mining in a typical ephemeral Mediterranean stream, namely the Rambla de la Viuda (eastern Spain). The aims of this work were to identify morphosedimentary changes and responses to human activities and floods, quantify river degradations and analyze factors favoring fluvial recovery for further applications in other rivers. Aerial photographs and LiDAR topography data were studied to analyze geomorphic evolution over the past 70years along a 7.5-km reach of an ephemeral gravel stream that has been mined intensively since the 1970s. To evaluate changes in the riverbed, we mapped comparable units applying morphological, hydraulic, and stability (based on vegetation density and elevation) criteria to 13 sets of aerial photographs taken from 1946 to 2012. A detailed spatiotemporal analysis of comparable units revealed a 50% reduction in the active section and a 20% increase in stable areas, compared to the conditions observed prior to gravel mining. Instream mining was first observed in 1976 aerial photograph covering already up to 50% of the 1956 riverbed area. River degradation since then was quantified by means of a LiDAR DTM and RTK-GPS measurements, which revealed a 3.5-m incision that had started simultaneously with gravel mining. Climate and land use changes were present but the effects were completely masked by changes produced by instream gravel mining. Therefore, river incision/degradation was triggered by scarcity of sediment and lack of longitudinal sedimentary connection, creating an unbalanced river system that is still adjusting to the present hydrosedimentary conditions.

The effects of season and sand mining activities on thermal regime and water quality in a large shallow tropical lake

Thermal structure and water quality in a large and shallow lake in Malaysia were studied between January 2012 and June 2013 in order to understand variations in relation to water level fluctuations and in-stream mining activities. Environmental variables, namely temperature, turbidity, dissolved oxygen, pH, electrical conductivity, chlorophyll-A and transparency, were measured using a multi-parameter probe and a Secchi disk. Measurements of environmental variables were performed at 0.1m intervals from the surface to the bottom of the lake during the dry and wet seasons. High water level and strong solar radiation increased temperature stratification. River discharges during the wet season, and unsustainable sand mining activities led to an increased turbidity exceeding 100NTU, and reduced transparency, which changed the temperature variation and subsequently altered the water quality pattern.

Accumulation and recovery capacity of heavy metals in sand mine ponds of the Otamiri River in Owerri, Nigeria

This study investigated the levels, index of accumulation and recovery capacity of heavy metals (Pb, Cd, Cu, Ni, Zn, Fe, Mn) in sand mine ponds of the Otamiri River in Owerri, Nigeria during the wet season of 2012. Water (WC) and sediment samples (SD) were collected from six sampling points, with WC 1-WC 3 and SD 1-SD 3 located within a derelict mine pond and WC 4-WC 6 and SD 4-SD 6 located within an actively mined pond. The pH was determined in situ and levels of heavy metals measured with the atomic absorption spectrophotometer. The student’s t-test, index of geoaccumulation (Igeo), accumulation factor (AF) and pond recovery capacity (PRC) were computed for the ponds. There was significant spatial heterogeneity in mean levels of the heavy metals in sediments (sig. t=0.029) at P Zn (4.932)> Cu (4.743) > Mn (4.326) > Pb (3.214) > Ni (2.483) > Cd (1.649), AF was Zn (1.513) > Cd (1.179) > Fe (1.082) > Ni (1.048) > Mn (1.042) > Cu (1.032) > Pb (0.987) and PRC was Zn (33.891) > Cd (15.165) > Fe (7.604) > Ni (4.608) > Mn (4.047) > Cu (3.052) > Pb (-1.373). Active mining led to extreme contamination of the ponds with Fe, strong to extreme contaminations with Cu, Zn and Mn, strong contamination with Pb, moderate to strong contamination with Ni and moderate contamination with Cd. However, Pb showed deficit recovery capacity and this could portend unfavourable ecological consequences on resident biota and raises public health concerns among resource dependants of the river. Strict enforcement of regulations on in-stream sand mining should be applied.

Oxbow Lakes as Indicators of River Channel Change: Leaf River, Mississippi, USA

This study uses oxbow lakes to ascertain the extent and nature of change in a river's form, focusing on the effects of post-1950s floodplain gravel extraction on the geomorphology of the Leaf River in southeastern Mississippi, USA. The river and oxbow lakes of a 5 km reach were examined for the effects of local and upstream floodplain and in-channel gravel mining. Data from 12 cross-sections suggests that the present-day river is 35% wider and 12% shallower than the cross-sectional geometry in cutoffs that pre-date 1955. Field measurements reveal that the Leaf River was relatively stable from at least 1911 to the early 1940s, but has since undergone an average of 2.65 m of degradation in the study reach. Survey data from a nearby USGS stream gage show that degradation began abruptly in the mid 1970s, most likely as a result of in-stream mining and pit avulsions on a major tributary that deprived downstream areas of bed load and created profile adjustments.

Water quality and dissolved inorganic fluxes of N, P, SO4, and K of a small catchment river in the Southwestern Coast of India

The southwestern coast of India is drained by many small rivers with lengths less than 250 km and catchment areas less than 6,500 km(2). These rivers are perennial and are also the major drinking water sources in the region. But, the fast pace of urbanization, industrialization, fertilizer intensive agricultural activities and rise in pilgrim tourism in the past four to five decades have imposed marked changes in water quality and solute fluxes of many of these rivers. The problems have aggravated further due to leaching of ionic constituents from the organic-rich (peaty) impervious sub-surface layers that are exposed due to channel incision resulting from indiscriminate instream mining for construction-grade sand and gravel. In this context, an attempt has been made here to evaluate the water quality and the net nutrient flux of one of the important rivers in the southwestern coast of India, the Manimala river which has a length of about 90 km and catchment area of 847 km(2). The river exhibits seasonal variation in most of the water quality parameters (pH, electrical conductivity, dissolved oxygen, total dissolved solids, Ca, Mg, Na, K, Fe, HCO(3), NO(2)-N, NO(3)-N, P[Formula: see text], P[Formula: see text], chloride, SO(4), and SiO(2)). Except for NO(3)-N and SiO(2), all the other parameters are generally enriched in non-monsoon (December-May) samples than that of monsoon (June-November). The flux estimation reveals that the Manimala river transports an amount of 2,308 t y(-1) of dissolved inorganic nitrogen, 87 t y(-1) dissolved inorganic phosphorus, and 9246 t y(-1) of SO(4), and 1984 t y(-1) K into the receiving coastal waters. These together constitute about 23% of the total dissolved fluxes transported by the Manimala river. Based on the study, a set of mitigation measures are also suggested to improve the overall water quality of small catchment rivers of the densely populated tropics in general and the south western coast in particular.

A review of sediment quantity issues: Examples from the River Ebro and adjacent basins (Northeastern Spain)

Sediment flows naturally through the drainage network, from source areas to deposition zones. Sedimentary disequilibrium in rivers and coastlines is related to the imbalance within the fluvial system caused mostly by dams, instream mining, and changes in land use. This phenomenon is also responsible for ecological perturbations in rivers and streams. A broad need exists to establish comprehensive management strategies (soft measures) that would go beyond site-specific engineering practices (technical measures) typically taken to solve particular problems. Long-term programs are also required to monitor sediment transport in river basins, in order to assess the magnitude and variability of sediment transfer and potential deficits. This paper shows examples of rivers with important sediment disequilibrium in the Ebro and adjacent basins. These basins, like most in the Iberian Peninsula, experience sediment discontinuity in the catchment-river-coast system. Reservoir siltation is the main quantitative issue. Land use change and especially gravel mining downstream from dams accentuate the process. We also present and discuss recent developments on water and sediment management undertaken to improve the morphosedimentary dynamics of rivers.

Environmental effects of river sand mining: a case from the river catchments of Vembanad lake, Southwest coast of India

Rivers in the southwest coast of India are under immense pressure due to various kinds of human activities among which indiscriminate extraction of construction grade sand is the most disastrous one. The situation is rather alarming in the rivers draining the Vembanad lake catchments as the area hosts one of the fast developing urban-cum-industrial centre, the Kochi city, otherwise called the Queen of Arabian Sea. The Vembanad lake catchments are drained by seven rivers whose length varies between 78 and 244 km and catchment area between 847 and 5,398 km2. On an average, 11.73 million ty−1 of sand and gravel are being extracted from the active channels and 0.414 million ty−1 of sand from the river floodplains. The quantity of instream mining is about 40 times the higher than the sand input estimated in the gauging stations. As a result of indiscriminate sand mining, the riverbed in the storage zone is getting lowered at a rate of 7–15 cm y−1 over the past two decades. This, in turn, imposes severe damages to the physical and biological environments of these river systems. The present paper deals with the environmental effects of indiscriminate sand mining from the small catchment rivers in the southwest coast of India, taking the case of the rivers draining the Vembanad lake catchments as an example.

Sediment mining in alluvial channels: physical effects and management perspectives

AbstractBased on a review of a number of documented case studies from various countries and a detailed analysis of sediment exploitation from five rivers in Italy and Poland, we discuss alluvial river response to extensive sediment mining. A sediment deficit caused by in‐stream mining typically induces upstream‐ and downstream‐progressing river incision, lateral channel instability and bed armouring. The resultant incision alters the frequency of floodplain inundation along the river courses, lowers valley‐floor water tables and frequently leads to destruction of bridges and channelization structures. Mining also results in the loss or impoverishment of aquatic and riparian habitats. In the rivers of Italy and southern Poland studied, where mining coincided with other human activities that reduce sediment delivery to the channels, deep river downcutting, changes in channel pattern and, in one case, transformation from alluvial to bedrock boundary conditions were recorded over recent decades.The type and magnitude of channel response to sediment mining depend mainly on the ratio between extraction and sediment replenishment rates. The effects of mining will be especially severe and difficult to reverse: (i) where material is extracted at a rate greatly exceeding the replenishment rate; (ii) in single‐thread rivers, that are generally associated with relatively low rates of catchment sediment supply; (iii) in channelized reaches; (iv) where rivers are underlain by a thin cover of alluvium over bedrock; and (v) where mining coincides with other human activities that reduce upstream sediment delivery. With a large number of detrimental effects of instream mining, the practice should be prohibited in most rivers except aggrading ones. Copyright © 2005 John Wiley & Sons, Ltd.

Sustainable river mining of aggregates in developing countries

Abstract Throughout the developing world, river sand and gravel is widely exploited as aggregate for construction. Sediment is often mined directly from the river channel and makes an important contribution to the national demand for aggregates. However, instream mining, if not carefully controlled, can cause significant damage to the river and its associated biota, and to the adjacent land, as well as creating conflict with other users of the river. The economic and environmental geology of river sand and gravel mining in developing countries is poorly known and there is little knowledge available to inform existing regulatory strategies. Research work on selected river systems in Jamaica and Costa Rica has generated a considerable amount of new information on resources and sediment budgets, on market and supply options, on the physical, biological and social impacts of extraction, and on best-practice legislative and mineral planning issues. A methodology has been developed for effective control of instream sand and gravel mining operations including a Code of Practice, which regulators can use for examining and reconciling the conflicting claims of sand and gravel extraction and the environment.

Imperilled rivers of Australia: Challenges for assessment and conservation

In Australia, riverine biodiversity (as judged by species diversity) is threatened by an array of anthropogenic effects common in industrialised countries (e.g. in-stream barriers, mining and sewage effluents, increased nutrient inputs, introduced species) as well as more diffuse, widespread phenomena characteristic of most of the arid and semi-arid areas of the world (e.g. salinisation and alteration of flows). Although much has been learned from specific case studies in the more populated areas, the nationally systematic efforts at quantifying these threats rely mostly on measures of river “condition” or “health” because measuring species diversity across areas as large as Australia is too expensive. However, these measures are incomplete representations of biodiversity, and some of the auditing processes compound other human values into their summaries of river condition or health. Furthermore, public perceptions of what rivers in Australia can deliver in terms of “ecosystem services” may not be feasible in many areas owing to the way that the Australian landscape has evolved. To avoid making the mistake of assuming that “good river health” automatically means “all biodiversity is conserved,” three advances are needed: appropriate conceptual frameworks of how a given river system functions, more research that clarifies the links between processes and biodiversity, and an understanding of the historical biogeography of the river biota so that we can provide a clear context for the first two items. Substantial progress has been made in developing and adapting conceptual models of river systems, research into processes is being initiated even in some remote, sparsely populated catchments, and much has been learned about the history and distribution of the flora and fauna. Key challenges remain in consolidating reliable empirical relationships between biodiversity and the surrogate variables used to measure it, estimating the rates of biodiversity change likely to accrue from climate change over the next millennium, and identifying biodiversity “hot spots” particularly for less than charismatic species.

Groundwater resources and quality variations caused by gravel mining in coastal streams

We study the effects of gravel mining on the aquifer–river system in the Baix Fluvià area (NE Spain). Field data show that instream mining has caused a decline of the water-table head of the unconfined aquifer along the Fluvià river. Further, dredging in its lowermost reaches reduces its stage and decreases its slope to zero, which facilitates mixing with sea-water, and thus salty-water intrusion from the river into the aquifer. A dimensionless solution of the Boussinesq’s equation is derived to estimate the water-table shape and the amount of groundwater lost as runoff for any given decline of the river stage. A flow and solute transport finite-element model is also used to calculate groundwater loses for the Fluvià case. We find that results of the general analytical solution are consistent with those of the numerical model, which reproduces the actual layered aquifer and a more appropriate domain geometry. Finally, the observed chloride distribution and time evolution are broadly reproduced using the numerical model. It shows that significant chloride plumes develop after the cone of depression of the nearby wells reaches the river. However, a natural clean-up takes place in the absence of pumping when the natural water gradient turns completely towards the river.