Gravel Mining Activity Impact on Riverbed Erosion and Bridge Foundation Stability

Geomorphological processes pose a risk that deserves attention and planning to avoid that, especially in the section near to east of Tuz bridge. This section of the valley facing a dramatic increase in gravel excavation and sorting of aggregates, consequence led to a change in the pattern of river branches flow from an anabranching river to a single-channel river, which led to a concentration of river discharge during floods. On 9th December 2018, Tuz Bridge was failed due to a heavy rainstorm three days preceding the failure event. The current study aims to conduct a field survey of all the human activities in the study area to assess river changes from remote sensing data the amount of runoff and river peak discharge based on rainfall data using SCS-CN method. In this study, ArcGIS, ArcGIS Earth, Google Earth, and WMS software are incorporated in the data analysis. The revealed results indicate the severe modification of valley morphology and converting the river pattern to flow during flood within a single channel with flow speed exceeded the critical velocity to induce vertical erosion of gravel and sands under the foundations of the bridge and causing the displacement and settlement of the bridge. The study recommends the local administration prevent gravel mining from the river valley at the upstream area of the bridge

STUDY OF PRODUCTIVITY ANALYSIS OF DIGGING LOADING IN GRAVEL MINING IN PT. GALUH CEMPAKA DISTRICTS CEMPAKA CITY BANJARBARU SOUTH KALIMANTAN PROVINCE

Galuh Cempaka Ltd. is a Gravel Mining Company with an area of 2,994 Ha. The mining system was surface mine or open pit. There are several things which should move in dig and load activities, such as mechanical soil, productivity, and compatibility of loading and conveying equipment are important factors in gravel mining activities. It influences on how far to know the effective work hour and the productivity. The purpose of this research was to determine work efficiency in Galuh Cempaka Ltd, and calculate the productivity of each equipment and the Match Factor value of the loading and conveying equipment in mining activity. From the observation and data processing, it obtained 1 unit of excavator Komatsu PC 400LC, wasingplan as far as 1.5 km. The effective work time was obtained work efficiency of 0.82 and after it was conducted the efficiency become 0.83 and it was reduced the obstacles from excavator CAT 320D. Before digging toll productivity got optimizing from CAT 320D in gravel excavation, it got 94.2 tons/hour and after it got optimizing from CAT 320D excavator in gravel excavation, it obtained 99.6 tons/hours and the IVECO 380 dump truck for gravel loading was 125.55 tons /hour. It obtained Match Factor Overburden (08) < 1. it means it is less than 1. So, there was waiting time for transportation equipment which had not arrived yet. Match Factor Gravel (1.2) > 1 means more than 1. So, there was a waiting time for transportation because the digging tool was filled.

Mapping Land-Use/Land-Cover Change in a Critical Biodiversity Area of South Africa

Land-use/land-cover (LULC) changes have implications for the long-term outlook of environmental processes, especially in the face of factors such as climate change. These changes can have serious consequences for humans. In this study, remote sensing and geographic information system methods were used to investigate LULC changes in a critical biodiversity area (CBA) in the northern sections of Limpopo Province in South Africa from 1990 to 2018 using data obtained from the South African National Land Cover project. In 1990, the dominant land cover comprised thickets and dense bush, followed by woodland and built-up areas, covering proportions of 40, 24 and 18% of the total land-cover area, respectively. Bare and forest areas were the least dominant classes during this time. In 2018, the dominant land cover was woodland, followed by built-up areas, comprising 71 and 20% of the total area, respectively. Subsistence agriculture is a land-cover class with a relatively higher area compared to water bodies, wetlands and other classes. Between 1990 and 2018, significant changes in land-cover were noted for thickets and dense bush, woodland, water bodies, subsistence agriculture and built-up areas. Woodland increased by over 1000 hectares (ha) per year, while thickets decreased by over 900 ha per year. Interviews were conducted with local residents to determine what they thought were the drivers behind the observed changes. According to these interviews, the drivers included deforestation, agricultural activities in wetlands, sand and gravel mining, among others. The study’s outcomes are critical for future land-use planning exercises and the long-term conservation of this CBA, an area rich in biodiversity and a strategic water source for the communities.

Short-term seasonal changes of the Dzita beach of Ghana using geographic information system and photogrammetry

Coastal erosion has become an issue globally. As the sea level continues to rise due to global warming, projections are that erosion would increase. To address the issue sustainably, relevant scientific information such as sediment transport and shoreline dynamics is required at local scales. Over the years, erosion at the eastern coast of Ghana has been mainly evaluated using low-resolution imagery due to the challenges in retrieving high-resolution data in the nearshore region. An unmanned aerial vehicle (UAV) approach was used to assess beach evolution on a seasonal and short-term basis between May 2018 and December 2019. Using the UAV approach, shoreline changes, sediment volume changes, and profile elevation parameters were extracted for the Dzita beach of Ghana. Shoreline changes indicated the dominance of erosion during the first and third phases (May 2018 to December 2018 and June 2019 to December 2019, respectively) at a rate of −7.23 ± 0.23 and −4.85 ± 0.23 m/yr, whereas the second phase showed accretion of +8.44 ± 0.23 m/yr. Beach profiles from the first, second, and third phases had steep and gentle slopes, respectively. From these observations, it was recommended that soft engineering approaches such as beach nourishment should be implemented to protect the shoreline and strict prevention of nearshore sand mining and gravel mining. It is also possible that the beach could go through a cycle of changes. Further studies using this same approach should be done as well as probing into other parameters such as nearshore bathymetry to have a better understanding of beach dynamics as envisaged.

Decadal sediment dynamics of a perturbed fluvial system: the case of the man-made Marecchia River canyon, Northern Apennines

&lt;p&gt;River canyons are transient geomorphic systems shaped by river incision into bedrock and coupled by instability of the adjacent valley walls. Investigating the evolution of river canyons is typically challenging due to the geologic time scales involved. In this context, the Marecchia River, which hosts in its intermediate portion a 6-km canyon, developed since the early 1950&amp;#8217;s following intense gravel mining, may be instructive. Indeed, this setting offers the opportunity to: (i) document canyon development through highly erodible pelitic rocks; and (ii) evaluate relevant upstream and downstream effects on fluvial morphodynamics. To these ends, we subdivide the 50-km stretch of the Marecchia River main stem into 22 homogeneous reaches and evaluate decadal geomorphic changes through analysis of LiDAR-derived digital elevation models (i.e., 2009 and 2019) in conjunction with planimetric changes of active channel width delineated on orthophoto-mosaics (i.e., 2009, 2012, 2014, 2017, 2019). The estimation of patterns and rates of fluvial erosion into bedrock and its geomorphic effects are essential for understanding landscape evolution and for applying sustainable sediment management plans.&lt;/p&gt;&lt;p&gt;In terms of volumetric changes, the entire river stretch recorded a decadal degradation of 2,516,150 m&lt;sup&gt;3&lt;/sup&gt; (57%) and 1,884,700 m&lt;sup&gt;3&lt;/sup&gt; of aggradation (43%), with a corresponding net volume loss of -631,450 m&lt;sup&gt;3&lt;/sup&gt;. Highest specific volumes of aggradation were observed in a homogeneous reach located in the lower part of the study segment (0.5 m&lt;sup&gt;3&lt;/sup&gt;/m&lt;sup&gt;2&lt;/sup&gt;), while highest values of degradation were observed in the upper reach of the canyon (-2.3 m&lt;sup&gt;3&lt;/sup&gt;/m&lt;sup&gt;2&lt;/sup&gt;). During the 2009-2019 period, knickpoint headward migration within the canyon has progressed for approximately 500 m, producing an average bedrock incision of about 10 m. As documented by area and volume changes, both rates of fluvial incision and canyon widening, as modulated by landslide activity and valley wall collapses, are highest in proximity of the main knickpoint and tend to decrease progressively downstream. By March 2019, when the second LiDAR survey was conducted, the main knickpoint had reached the foundations of a major check dam, which eventually collapsed two months later. Upstream of the canyon, channel reaches displayed narrowing dynamics with an alternation of degradation and aggradation processes. In terms of total volumetric changes, these reaches presented an indirect correlation with confinement, with the most confined reaches acting as sediment transfer zones. In contrast, the segment downstream of the canyon displayed widening dynamics (+ 11 m on average) together with an increase of aggradation processes. Due to the pelitic nature of the hosting bedrock, despite the high geomorphic change observed, most of the material supplied by the canyon walls gets transported in suspension, contributing very little to the estimated budget of the Marecchia River's distalmost reaches. In this way, we argue that most part of the aggradation observed in this segment was originated upstream, bypassing the canyon.&lt;/p&gt;

Ecological and environmental factors affecting the foraging activity of the White-bellied Heron Ardea insignis (Hume, 1878) in Bhutan

Summary White-bellied Heron Ardea insignis (WBH) is critically endangered, but we lack data on many aspects of its basic ecology and threats to the species are not clearly understood. The goal of this study was to analyse WBH foraging microhabitat selection, foraging behaviour, and prey preferences in two river basins (Punatsangchhu and Mangdechhu) in Bhutan which are likely home to one of the largest remaining populations of WBH. We also explored the relationship between the relative abundance of the WBH and prey biomass catch per unit effort within four foraging river microhabitats (pool, pond, riffle and run). Prey species were sampled in 13 different 100-m thalweg lengths of the rivers using cast nets and electrofishing gear. Riffles and pools were the most commonly used microhabitats; relative abundance was the highest in riffles. The relative abundance of WBH and prey biomass catch per unit effort (CPUE) also showed a weak but significant positive correlation (rs = 0.22). The highest biomass CPUE was observed in riffles while the lowest was found in the ponds. From the 97 prey items caught by the WBH, 95% of the prey were fish. The WBH mainly exploited three genera of fish (Garra, Salmo, and Schizothorax) of which Schizothorax (64%) was the most frequently consumed. This study provides evidence in support of further protection of critical riverine habitat and fish resources for this heron. Regular monitoring of sand and gravel mining, curbing illegal fishing, habitat restoration/mitigation, and developing sustainable alternatives for local people should be urgently implemented by the government and other relevant agencies. Further study is also required for understanding the seasonal variation and abundance of its prey species in their prime habitats along the Punatsangchhu and Mangdechhu basins.

Dynamic changes in the lower Gállego River (Ebro Basin, NE Spain) and their relationship with anthropic activities and the quaternary substrate

The lower Gállego River has been strongly degraded since the 1960s due to human activity (gravel mining, dump accumulation, channeling works), which has produced a deep channel incision. Although these human-driven processes are usually reported in fluvial bibliography, in this case, more complex results are observable. For instance, regarding the depth and incision rates, we observed no relationship between the most anthropically impacted areas and the sections with the deepest incisions; moreover, the deepening process continues 40 years after the human interventions ceased. The reason for this maladjustment is the role played by the exhumation of the underlying Pleistocene substrate, affected by the synsedimentary processes of karstification. The appearance of paleodolines filled with fine sediments on the incision bottom and sides is the main factor conditioning the continuity and magnitude of the process. Besides, these paleodepressions direct the river dynamics and course, thus favoring its widening when they appear and causing the development of a new riverbed (Qt13) while the 1960s floodplain (Qt12) is becoming an old terrace located between 5 and 11 m above the new alluvial bottom. There are no previous records about this kind of consequences in the regional fluvial dynamics.