Landform Changes Research Articles

Impact analysis of cyclonic effects and landform change in part of Indian Sundarban using remote sensing and Google Earth Engine

Impact analysis of cyclonic effects and landform change in part of Indian Sundarban using remote sensing and Google Earth Engine

The Impact of River Landform Changes Caused by Geohazards on the Economic Development of Ecotourism in Sabah, Malaysia

The impact of river landform changes caused by geohazards on the economic development of ecotourism in Sabah, Malaysia is a highly significant and crucial topic that necessitates extensive analysis, comprehension, and thorough understanding in order to comprehend the multifaceted consequences and ramifications. It is imperative to explore and scrutinize the intricate interplay between the alterations in river landforms induced by geohazards, such as natural disasters and environmental upheavals, and their profound influence on the economic growth and prosperity of the burgeoning ecotourism sector in Sabah, Malaysia. This comprehensive investigation holds immense value in unraveling the intricate dynamics and intricacies inherent in this intricate and complex relationship. By delving deep into the intricate mechanisms and multifarious aspects that underlie the interdependence of geohazards-induced river landform transformations and the economic development of ecotourism in Sabah, Malaysia, researchers and stakeholders alike can gain invaluable insights that can pave the way towards well-informed decision-making, sustainable growth, and effective management strategies. Consequently, the expansion of knowledge and understanding in this pivotal domain can potentially lead to the formulation and implementation of robust measures, policies, and initiatives that can mitigate the adverse effects of geohazards on river landforms, foster the resilience and adaptability of the ecotourism industry, and ultimately cultivate a harmonious balance between economic progress and environmental conservation in Sabah, Malaysia.

Comparative Study of the Coastal Geomorphology of Kajirbhati Sand-Spit Using Google Earth Pro Images (2005, 2011, 2023) and Landsat Satellite Data (2009, 2016, 2023): An Approach Towards the Impact of the Casuarina Plantation

Coastal geomorphology undergoes constant transformation due to a combination of coastal and fluvial processes and human intervention. Remote sensing and GIS tools are invaluable in identifying and studying these changes. Due to the dynamic interaction between land and sea, the coastline requires careful monitoring to detect hotspots and understand the spatial and temporal impacts of climate change on the coastal environment. Remote sensing data offers a comprehensive means of studying coastal landform changes. In a recent study, the focus was to analyze the impact of the Casuarina plantation on the coastal geomorphology of Kajirbhati spit. This involved studying various depositional features such as sand bars, sand spits, dunes, and beaches. The study utilized Google Earth Pro images from 2005, 2011, and 2023 to digitize 13 classes each year, enabling the identification of changing geomorphic classes. These include agriculture, swash zones, dunes on sand spits, berm lines, Casuarina and coconut plantations, estuary, mangroves, mudflats, open land, sea, settlement, and vegetation. The results revealed dramatic changes in land use and land cover classes from 2005 to 2023. In the years from 2011 to 2023, the area of sandspit covered by Casuarina plants expanded rapidly. To analyze the changes, Landsat 5, 8, and 9 data were used to check the intensity of NDVI (Normalized Difference Vegetation Index) in 2009, 2016, and 2023. NDVI is a critical factor in this research. The mean NDVI values for 2009, 2016, and 2023 were -0.002, 0.02, and 0.04 respectively. The changes in higher NDVI values from 2009 to 2023 were -0.10, 0.27, and 0.28, while the lower values were -0.10, -0.10, and -0.07 for the same years. The correlation calculation between the mean NDVI values and the years indicates a strong positive correlation with an R-value of 0.99. Casuarina plants play a crucial role in protecting the coast from strong winds and dynamic sea waves. They help protect mudflats, mangroves, settlements, and estuary land use and cover classes along the coast of Kajirbhati.

Delineating the climate change impacts on urban environment along with heat stress in the Indian tropical city

India experiences significant levels of temperature variance as a result of urbanization, deforestation, and industrial growth, all of which contribute to a progressive increase in heat island effects. Significant landform change has occurred in Bhubaneswar City, Odisha, in recent decades as a result of major plant loss and temperature unpredictability. Thus, during the summer and winter months, an examination of the long-term heat island impacts is essential for Bhubaneswar. The evolution of landforms and heat island impacts in Bhubaneswar are evaluated using Landsat images from 1991 to 2021 datasets and correlation analysis of heat islands and geospatial variables. Between 1991 and 2021 with a 10-year gap, the landforms studied showed an increase in built-up land (38.009 km2), a decrease in vegetation (13.875 km2), bare ground (16.306 km2), and water bodies (7.828 km2). The annual temperature variance in Bhubaneswar was 0.124 °C (summer), and 0.293 °C (winter). Surface temperatures varied by about 3.71 °C (summer) and 8.80 °C (winter). During the study years, heat islands increased from 2.89 to 4.27 (summer) and 2.30 to 3.87 (winter). In Bhubaneswar, there was an increase in ecological variation of 0.092 (summer), and 0.071 (winter). There is a statistically significant negative correlation between the R2 values and the temperature and the built-up indices. Using this dataset, administrative and development authorities can choose which measures to take to counteract the effects of variations in thermal variation. Finding out how man-made land use structures, industrial zones, and other areas contribute to the built-up area a direct consequence of heat islands was the aim of this study.

Methodology for Performing Bathymetric and Photogrammetric Measurements Using UAV and USV Vehicles in the Coastal Zone

The coastal zone is constantly exposed to marine erosion, rising water levels, waves, tides, sea currents, and debris transport. As a result, there are dynamic changes in the coastal zone topography, which may have negative effects on the aquatic environment and humans. Therefore, in order to monitor the changes in landform taking place in the coastal zone, periodic bathymetric and photogrammetric measurements should be carried out in an appropriate manner. The aim of this review is to develop a methodology for performing bathymetric and photogrammetric measurements using an Unmanned Aerial Vehicle (UAV) and an Unmanned Surface Vehicle (USV) in a coastal zone. This publication shows how topographic and bathymetric monitoring should be carried out in this type of zone in order to obtain high-quality data that will be used to develop a Digital Terrain Model (DTM). The methodology for performing photogrammetric surveys with the use of a drone in the coastal zone should consist of four stages: the selection of a UAV, the development of a photogrammetric flight plan, the determination of the georeferencing method for aerial photos, and the specification as to whether there are meteorological conditions in the studied area that enable the implementation of an aerial mission through the use of a UAV. Alternatively, the methodology for performing bathymetric measurements using a USV in the coastal zone should consist of three stages: the selection of a USV, the development of a hydrographic survey plan, and the determination of the measurement conditions in the studied area and whether they enable measurements to be carried out with the use of a USV. As can be seen, the methodology for performing bathymetric and photogrammetric measurements using UAV and USV vehicles in the coastal zone is a complex process and depends on many interacting factors. The correct conduct of the research will affect the accuracy of the obtained measurement results, the basis of which a DTM of the coastal zone is developed. Due to dynamic changes in the coastal zone topography, it is recommended that bathymetric measurements and photogrammetric measurements with the use of UAV and USV vehicles should be carried out simultaneously on the same day, before or after the vegetation period, to enable the accurate measurement of the shallow waterbody depth.

Urban sprawl, urban form, and urban land use pattern: examining urban planning response to the causes and effects of urban sprawl in Kumasi, Ghana

ABSTRACT Unplanned urbanization continues to threaten the sustainability of cities in the global south. This study seeks to assess the urban planning response to the effects of sprawl on the urban form and land use pattern of Kumasi. The study relied on geospatial techniques to determine changes in land use patterns, landforms, and sprawl. A qualitative research approach was used to examine urban planning response to the causes and effects of urban sprawl in Kumasi. The results of this study show that the higher the urbanization rate, the more the built-up area increases, causing a significant loss of natural assets such as farmlands. In terms of shape, the research showed that the Greater Kumasi Metropolis has shifted from the historically monocentric city structure to a polycentric city. The city currently has multiple centers or subcentres for commercial, cultural, and social activities. In spite of all the threats posed by urban sprawl on the metropolis, there no clear policy intervention put in place to address the adverse effects of sprawl in the Greater Kumasi Metropolis. The researchers recommend that city authorities should adopt the compact city approach to control the high rate of sprawl to promote densification.

Identification of Marine Landforms as a Form of Coastal Area Management in Pangandaran District

Changes in marine landforms in coastal areas are relatively rapid and need to be analyzed to determine environmental management policies. Complex marine landforms are found in the coastal areas of Pangandaran Regency and have strong pressure to fulfill community activities, not only for local communities but also for outside communities. Basically, community activities are adapted to regional environmental conditions. The aim is to optimize the potential of natural resources and minimize environmental degradation, but in reality, this has not been fully implemented. The method used in this research is a descriptive method using a field survey approach. Marine landforms resulting from the accretion process in the Pangandaran coastal area are spit landforms, aeolian-marine sedimentation in the form of coastal dunes, fluvio-marine sedimentation in the form of estuaries and alates, organic-marine landforms and white sand beaches associated with reefs. The landforms resulting from erosion are Cliffs, notches, wave-cut platforms, stacks, and stumps. The impact of landforms resulting from sedimentation in the Pangandaran coastal area is mainly spit landforms that cover river mouths and the occurrence of flooding, puddles, and even accumulation of organic waste, landforms resulting from erosion, the impact of which is the decline of the coastline accompanied by avalanches of material towards the sea, especially on beaches that have non-resistant rocks such as sedimentary rocks and alluvial deposits. Management of the Pangandaran coastal environmental area must be carried out in an integrated manner, land buritan (hinterland), which has steep slopes and resistant rock, is designated as limited production land, and the development of the spit at the river mouth is made into a jetty, and the beach has beach cups waves with rip currents and water bathymetry. -10 meters above sea level, a wave-protecting wall must be built, and the coastal border area must be used as vegetative-based conservation land.Keywords: Marine landforms, Coastal Management, Pangandaran

Sedimentation record of a complete glacial-interglacial cycle: Down-slope deposits, contourites and plumites of the North Sea trough mouth fan

Trough mouth fans (TMFs) are major submarine depocentres that form in front of ice streams advancing onto the continental shelf, and they provide extensive records of past glaciations and ice-sheet dynamics. However, early research about TMFs was conducted using primarily 2D seismic data, which limits the insights on the deposit's geometries and internal structures and more recent studies using 3D data have focused on the general depositional history of TMFs. Here, we assess the spatial and temporal changes of the glacio-marine landforms and deposits throughout the last glacial-interglacial cycle (Marine Isotope Stage (MIS) 6 to 1, ∼130 ka to present) recorded in a >550 m thick progradational sequence. We use 3D reflection seismic data with significant vertical resolution (up to 2 m) imaging over 14000 km2 from the uppermost North Sea Fan (NSF) to document the seismic stratigraphy and sedimentary processes, by combining horizon picking and geomorphological analyses. The studied interval comprises five mappable units, four on the slope and one on the shelf, spanning from the modern seabed down to the top of the Tampen Slide (∼130 ka). Five different channel types (here included slide scars), as well as contourite and plumite packages are described based on their seismic facies, morphology, geometry, and stratigraphical position. We propose that contour currents are responsible for sediment delivery after the Tampen Slide deposition during the interglacial period before the onset of the Last Glacial Maximum, when high meltwater influx from the shelf produced turbidites. Sedimentation became debris-flow-dominated towards the end of the period of shelf-edge glaciation. The deglacial interval is characterized by the deposition of plumites on the slope. On the shelf, subglacial tills are deposited during both glacial and deglacial periods. We calculate an average sedimentation rate of <1 m/kyr during the interglacial (MIS 5-3), and around 50–65 m/kyr during the glacial and deglacial periods (MIS2-early MIS1). Thus, we document a change of two orders of magnitude in sedimentation rate during a glacial cycle on the slope of a glaciated margin.

Research Report of the Creative Inspiration of Oil Painting Landscape in Northwest China

The landscape has regional characteristics, rich landform changes and distinct seasons, which provides a good inspiration for artistic creation. This study collects and collates landscape materials through field investigation; the system analysis method is used to study the creative drawing process and artistic characteristics of oil painting landscape in Northwest China. Summarize the importance and flexibility of creative inspiration. The study found that creative inspiration is flexible and diverse, fleeting, and requires the artist’s keen insight to capture. This study provides theoretical support for further research on the inspiration of oil painting character creation.

Application of non-contact video quantitative measurement method in reservoir bank landslide monitoring

The geological structure of the reservoir bank landslide is complex and intricate. After deformation and damage, it causes river blockage, surges, and loss of people’s lives and property, posing a huge threat. At present, in academia and engineering applications, a large number of techniques such as inclinometers, rain gauges, and surface GNSS deformation monitoring are still used for monitoring landslides on reservoir banks. This type of monitoring method has the problem of “point to surface” which can easily lead to missed detection and reporting in some areas, some disaster points are close to water and steep, difficult to reach, and equipment installation is difficult. This work designs and implements a non-contact video quantitative monitoring system for surface deformation of geological disaster. By constructing a deep learning neural network, deformation area recognition and displacement quantitative calculation are achieved; By obtaining continuous images for a long time, draw the surface displacement-time curve, and output the surface deformation data and landform changes of the disaster. Meanwhile, this work explores the impact of different lighting conditions on the recognition results of target areas. This work can provide non-contact monitoring methods and dynamic warning support for large-scale monitoring of geological disasters.

Impact of large wood on sediment (dis)connectivity in a meandering river

Large wood (LW) can exert strong influence on sediment storage patterns in fluvial systems. However its specific impact on sediment routing is largely dependent on the stability of individual LW pieces or LW jams. We used sediment (dis)connectivity principles to quantify the impact of LW on sediment erosion and storage along a meandering river reach. Decadal spatiotemporal changes of LW and fluvial landforms are appraised along a 3.65 km long reach of the Odra River (Czechia). Detailed orthophotos at two-year intervals from 2012 to 2022 are analysed alongside field inventories. During this study period, there was a single flood event with a 5–10-year recurrence interval, and three smaller flow events with a recurrence interval of up to 2 years. We assessed the sediment deposition, bank protection, and erosion effects of LW, finding that the impact of LW on decelerating sediment fluxes was more pronounced. Specifically, LW-related deposition varied between 13.6 m2 and 36.7 m2 per 100 m of channel length during the individual two-year periods. In contrast, we detected only 0.5 m2 to 7.8 m2 per 100 m of channel length of newly eroded material during the same periods. Additionally, 6.3 % to 7.8 % of the lengths of the outer meander bends were protected by persistent LW elements against erosion during these two-year periods. Finally, we developed a three-stage conceptual model depicting the impact of LW on sediment (dis)connectivity in a meandering river at different relative timescales. Our model accounts for the dependence of interactions between LW and fluvial sediments based on the LW stability and frequency-magnitude of the hydrogeomorphic processes. In general, our observations suggest that the presence of stable LW in meandering rivers primarily leads to the deceleration of the lateral and longitudinal dimensions of sediment (dis)connectivity.

Applicability of the Surplus Map to Small Landform Changes on River Bank and Its Surroundings: Case Study of the Kinu River

Applicability of the Surplus Map to Small Landform Changes on River Bank and Its Surroundings: Case Study of the Kinu River

Spatio-temporal analysis of geomorphic recovery along an altered ephemeral stream using automated image processing

Ephemeral rivers in the Mediterranean region have been exposed to significant human disturbance over the last century. Recently, there has been a growing interest in restoring their morpho-sedimentary condition, backed by the European Water Framework Directive. Previous research has highlighted the severe geomorphic impacts of sediment extraction, such as reduced channel width and riverbed incision, but the recovery of these channels during annual flows remains poorly understood. This study presents a methodological framework to investigate geomorphologic recovery (signs of landform change) and constraints in the Rambla de Cervera (eastern Spain) from 2018 to 2021. Aerial imagery, LiDAR topography, and field surveys were used for stream segmentation, fluvial landform classification, temporal landform change, and comparison with flow characteristics from a 2D hydraulic model. The study identified three groups of segments with different channel types and recovery mechanisms. Upstream (G1), unconfined valley settings showed minor changes, indicating morphological stability. Middle segments in confined valleys (G2) showed greater alluvial channel recovery and vegetation encroachment in response to flood/no-flood periods. Downstream segments (G3), incised on cemented gravel, were highly responsive to floods but lacked landform stability due to high energy conditions. The findings suggest that channel recovery during annual floods is slow and occurs mainly downstream in degraded areas (G3). Increased sediment flux from upstream and additional sediment storage in new forms are required to recover these channels. This analysis underscores the challenge of interpreting short-term morpho-dynamic changes for long-term river recovery, but provides insight into the morpho-sedimentary conditions required to accelerate recovery of ephemeral streams.

How does landslide debris grain size control sediment transport and dynamics?

The grain size of sediment delivered to a river by hillslope processes is an important factor which could impact fluvial erosion, sediment transport, and associated geomorphic changes. Grain size distribution (GSD) is increasingly recognised as an important factor for the impact of landslides on sediment pulses and long-term erosion rates. Therefore a better comprehension of grain size control on landslide-generated sediment transport and dynamics will help with understanding post-seismic fluvial processes and landscape evolution. In this study, we modelled the recovery of the Hongxi River basin affected by the Wenchuan earthquake under different landslide GSD scenarios. The CAESAR-Lisflood (CL) model was first modified to enable the spatial input of sediment GSD, which allows the model to distinguish the grain size composition of landslide sediment and the background sediment sourced from other areas. Using the modified CL model, we simulated three different landslide GSD scenarios (Original, Coarser, Finer) by altering the original landslide sediment GSD observed from a post-earthquake basin. In particular, we analysed the fate of landslide-generated sediment using a new sediment tracing function embedded in CL. This enabled us to evaluate the role of landslide GSD variation on the spatio-temporal heterogeneity of sediment transport. Our results show that the GSD of landslide material exerts a clear control on both sediment yield and channel deposition, the sediment transport of landslides disconnected to the fluvial system is more sensitive to grain size variation, while the GSD of landslides connected to the fluvial system has less impact on sediment dynamics. The duration of landslide disturbances on basin sediment dynamics can largely be dependent on the period of time (e.g., 20 years in this study basin) taken for grain coarsening (the grain size is increasing upward), which is dominated by the evacuation of fine sediments. The modelling results and findings highlight the importance of grain size distribution of landslide material and provide information to support basin sediment management and environmental risk mitigation.

Changes in Coastal Landforms from the Poonaryn Peninsula to the Malwathu Oya (Aruvi Aru) Estuary, Northwestern Coastal Zone (NWCZ) of Sri Lanka

Changing coastal landforms are constantly occurring due to wind, waves, sea currents, tidal fluctuations, and human interference. This paper makes a special effort to ensure the correct usage, management and utilization of these landforms, which will benefit society through economic growth. A variety of peculiar coastal landforms have formed between the Poonaryn Peninsula (9°36'10.23"N, 80°03'16.74"E) and Malwathu Oya (Aruvi Aru) estuary (8°46'30.22"N and 79°56'12.85"E), which are approximately 120 km long coastal stretch. The Poonaryn Peninsula extends from Pallikuda Beach to Kalladi Yutha Kovil (9°35'53"N, 80°3'10"E). The peninsula stretches northwest to southeast, covering dunes with a maximum elevation of 17 meters. The selected study location is favourable for the coastal environment, and the coastal environment can be defined as the area lying at the interface between land and Mannar Bay, Palk Bay and a part of the Jaffna Lagoon. This area includes non-barrier delta estuaries with seasonal rivers and bar-built perennial delta estuaries. The zone of shallow water within which waves can move sediment and the area landward of this zone, including beaches, low coastal dunes and vegetation cover, are affected to some degree by the direct or indirect effects of waves, tides, winds and currents. The coastal environment itself may extend inland for many meters or kilometers. These processes make it possible to identify several coastal habitats, such as mangroves, salt marshes, covered and covered dunes, beaches, barrier beaches and spits. Lagoons, riverine estuaries, brackish water bodies, water holes, and marshes. When considering biodiversity, local and migratory avifauna, beach mangroves, seagrass beds, tidal creek system are very important for tourist attraction. Additionally, fishery harbours, boat landing sites, traditional fisheries (beach seines, koodo fishing), etc., and tourism were established in the northwestern coastal stretch owing to enticing coastal processes and landforms in the area for correct usage, management and utilization for enormous benefits of the fishing society, the environment and the economy.

Multiple Close-Range Geomatic Techniques for the Kinematic Study of the La Paúl Rock Glacier, Southern Pyrenees

Rock glaciers are one of the most representative elements of mountain permafrost. Their study can contribute to modelling climate change and its effect on natural and anthropogenic environments. Therefore, it is crucial to understand the evolution and quantify the changes in these periglacial landforms at a global level. This study aims to present the monitoring work carried out on the Pyrenean rock glacier of La Paúl (42°39′40″N, 0°26′34″E) from 2013 to 2020, employing in situ geomatics techniques to determine the landform surface kinematics accurately. For this purpose, global navigation satellite systems (GNSS), terrestrial laser scanners (TLS), and unmanned aerial vehicles (UAV) photogrammetry techniques were used simultaneously to evaluate their compatibility in quantifying displacements. Based on 2D and 3D analyses, the results demonstrate the high surface activity of the rock glacier, with mean variations reaching 36 cm/year (GNSS) and a distribution of deformations that, although intensified on its western side, are present on the entire surface of La Paúl. This study uses state-of-the-art geomatics techniques to present dependable and updated quantitative data on a periglacial landform’s recent development in under-researched areas, such as the Pyrenean temperate high mountain.

Aero Mapping Application for Affected Area Detection by the Semeru Volcano Eruption in 2022

The development of geospatial technology, especially Unmanned Aerial vehicles (UAV) or drones, has been growing rapidly. One of the uses of UAV is to detect disaster hazards, the extent of the affected area, and the element of risks. The latest UAV technology in the form of Aero Mapping is beneficial for mapping disaster-affected areas, in this case, post-volcanic eruption lava flows. Aero mapping with the rotary wing type is low-cost (<$ 2000/Rp.29.500.000) but a potent tool for collecting spatial data quickly and accurately. This application is applied to detect areas affected by volcanic eruptions. The photo image produced by the UAV can be used to analyze lava flows, lava deposits, changes in landforms, and changes in land cover due to volcanic eruptions. This study aims to detect the area affected by the eruption of Semeru Volcano post-eruption in 2022. In the research study area, there is no detailed scale mapping can detect the direction/path of post-eruptive lahars. This research seeks to detail the description of the affected areas. The results of aerial photographs show that low-cost UAVs are capable of producing high-resolution data of up to 2.86 cm/px (Orthomosaic), 6.94 cm/px (DSM), and 3.94 cm/px (GSD) with a total area of up to 755 Ha. This area is obtained from 34 flight processes at an altitude of 120 meters with 70% front and side overlap. These findings prove that aero mapping is a low-cost technique that can be used to map new lava flows after the 2022 eruption at Semeru Volcano.

Seismic and hydrological triggers for a complex cascading geohazard of the Tianmo Gully in the southeastern Tibetan Plateau

On 11th July 2018, a destructive rock-ice avalanche and subsequent glacier debris flow occurred in the Tianmo Gully in the southeastern Tibetan Plateau (SETP). However, the source area and triggering factors of this cascading geohazard event remained unclear. In this study, we combined satellite remote sensing, meteorological observations, numerical modeling, and post-event field investigation to comprehensively analyze its evolution processes and potential triggers. The remote sensing observations of terrain and landform changes suggest that the initial avalanche occurred on the southeastern flank of the glacier, releasing approximately 2.77 × 106 m3 of lithic and ice material. From our analysis, we suggest that the complex evolution process of this cascading geohazard event could be manifested as earthquake and hydrological triggers → an initial rock-ice avalanche → glacial debris flow → triggered landslides → landslide dam → dammed lake. Our results suggest that the 2017 Ms. 6.9 Nyingchi earthquake, the unusually high meltwater from snow and ice during the abnormally warm and dry summer in 2018, and the short-duration intense rainfall (22 mm on 10 July) recorded one day before the event are the three main factors for the catastrophic event. These factors caused the rock-ice avalanche in the source zone and subsequently cascaded glacial debris flow and shallow landslides. This study highlights the urgent need for regular monitoring of high-risk glaciers, including anomalous changes in temperature and precipitation, and accelerated movements of glaciers due to earthquakes, especially in the SETP, where climate warming will be expected to intensify occurrences of such cascading geohazard events in the future.

Phylogeography and demographic history of the cyprinid fish Barbodes semifasciolatus: implications for the history of landform changes in south mainland China, Hainan and Taiwan

Hainan Island and Taiwan Island are adjacent to the southern margin of mainland China and Vietnam. During glacial periods, global sea levels dropped, allowing that the land bridges connected the continental island and mainland, connecting rivers and providing dispersal opportunities that shaped the origin and diversification of freshwater fishes. Barbodes semifasciolatus is distributed in various water systems of Vietnam, Hainan, Taiwan, and southern mainland China and is restricted to the southern region of the Min River. Our study aimed to evaluate the genetic diversity and phylogeography of B. semifasciolatus using the mtDNA cyt b gene (1,141 bp). A total of 107 haplotypes were identified from 395 specimens in 23 populations, and high haplotype diversity (1.000) and low nucleotide diversity (0.0134) were detected. Mitochondrial phylogenetic analysis and haplotype network analyses revealed three major lineages according to geographical distribution. Lineage A was mainly distributed in Hainan Island, Vietnam and the southern region of the Pearl River in mainland China. Lineage B was distributed only in southeastern Hainan Island. Lineage C was distributed in the coastal rivers of mainland China and Taiwan. We suggest that the river in the Guangdong region is a colonization route in South Taiwan and that the populations distributed in the Pearl River region moved southward to Hainan Island and Vietnam based on the network and Bayesian binary MCMC (BBM) analysis. Our demographic history results indicated that the populations of B. semifasciolatus experienced a bottleneck event following a recent population expansion (DECINC model) supported by ABC analysis. We suggest that sea-level changes exerted pronounced effects on the demography of B. semifasciolatus on the continental island and in the mainland during the late Pleistocene glacial cycles.

Short-Term Responses of Aquatic Ecosystem and Macroinvertebrate Assemblages to Rehabilitation Actions in Martil River (North-Western Morocco)

This study aimed to evaluate the effects of the Martil River rehabilitation project and recently constructed dam infrastructures to reduce flood risks and to promote local socio-economic development on the ecological integrity of the river. The assessment focused on changes in fluvial landforms over time and the evaluation of aquatic ecosystems based on six physicochemical parameters (temperature, pH, electrical conductivity, dissolved oxygen, biochemical oxygen demand, and chemical oxygen demand), morpho-hydrological variables (stream width, water depth, and current speed), habitat indices (QBR, IHF, and MQI), and macroinvertebrate assemblages of EPT, OCH, and Chironomidae (Diptera) at five stations from autumn 2015 to spring 2018 (prior to and during the rehabilitation actions). The results showed that the river rehabilitation project led to profound changes in Martil River’s ecosystem and water quality over time. Physicochemical and habitat measurements at the rehabilitated sites revealed a major change in macroinvertebrate communities due to changes in fluvial landforms in relation to flow-sediment regimes. As a result, some typical species of lentic habitats disappeared, while alien, opportunistic, and lotic species appeared.