Stream Gradient Research Articles

Long‐termstream hydrology and meteorology of a Polar Desert, theMcMurdoDry Valleys, Antarctica

AbstractThe McMurdo Dry Valleys (MDVs; 77.50°S, 162.25°E) make up the largest ice‐free region of Antarctica at ~3500 km2. Their position near the coast of the Ross Sea provides for a milder climate than much of the rest of the continent. Alpine and piedmont glaciers in the MDVs melt during the austral summer providing water to down gradient streams and terminal lakes on valley floors. There are currently 14 meteorological stations and 17 stream gauges operating across the MDVs, some with continuous records that go back to 1969. This relatively high density of monitoring stations reflects the fact that glaciers of different sizes and elevation ranges are the main source of water to streams. Thus, each glacier represents a different watershed. The bulk of these records start in the late 1980s/early 1990s. These data collection activities directly support research endeavours of the McMurdo Dry Valleys Long Term Ecological Research project, as well as a host of other science groups working in the MDVs. As such, both real time data and archived data from these sites is available through the online database interface of the project (http://mcmlter.org).

Tectonic implication in the evolution of lake and Quaternary landforms in the Lohawati river basin, Kumaun outer Lesser Himalaya

The evolution of the Quaternary landforms in the Champawat area of the outer Kumaun Lesser Himalaya is reconstructed from the paleolake sections and the geometry of the landscape. Conjugate sets of normal faults are observed in both the bedrocks and Quaternary deposits at Banlek. The most prominent normal faults are those striking NE-SW and NW-SE and most of them are steeply dipping faults while some are vertical faults. Sediments akin to the lacustrine deposits are observed at four sites; while the contact between the bedrock and the lake sediments is observed at only one site in the peripheral side. The exposed sediments thicknesses vary from 8.30 m to 4.8 m and consist of an alternation of black carbonaceous mud and sandy horizons indicating different depositional regimes. The total thickness of the lake sediments appears to be more than 75 m as deduced from elevational differences between the exposed sites. From Site 1, two OSL samples collected from 2.5 m and 8 m from the present ground surface, were analyzed which give OSL ages of 16 ka and 17 ka, respectively; while one sample collected from Site 4 gives an OSL age of 13 ka. A total of 3653 lineaments were mapped encompassing 2,277.8 sq km from the eastern Kumaun Himalaya. Maximum of the lineaments trend ENE-WSW or almost E-W (∼46.5%); the major principal stress is deduced to be in NE-SW direction. Lake, mature topography and gentle stream gradient in the Champawat area are the result of highly weathered bedrocks and development of the normal faults.

Numerical Investigation on a Flash Flood Disaster in Streams with Confluence and Bifurcation

On 20 August 2019, a flash flood occurred in Sanjiang Town, Sichuan, China, and caused great damage to people living there. The town lies at the junction of five streams, with streams A, B, and C combining at the town and further dividing into streams D and E. The slope of streams A, B, and C is about 3~5%, while the slope of streams D and E is around 0.3%. The Sanjiang Town actually lies in the transition from supercritical slope to subcritical slope. During the flood, huge sediments were released to streams A, B, and C, and further transported to stream E. Due to the rapid change of velocity, only few sediments deposited at the supercritical slope parts of the stream, while plenty of them sedimented at the streams with subcritical slope. In order to simulate the flood with a hydrodynamic model, a field investigation was carried out to collect high DEM (digital elevation model) data, flood marks, sediment grading, etc., after the flood. The discharge curve of the flood was also obtained by the hydrometric station near Sanjiang Town. For the inlet sediment concentrations of streams A, B, and C, we made a series of assumptions and utilized the case which best fits the flood marks to set the inlet sediment concentration. Based on these data, we adopted a depth-averaged two-dimensional hydrodynamic model coupled with a sediment transport model to simulate the flash flood accident. The results revealed that the flash flood enlargement in confluence streams is mainly induced by the inflows, and the flash flood enlargement in bifurcation streams is largely affected by the sediment deposition. The bifurcation of flows can decrease the peak discharge of each branch, but may increase the flooded area near the streams. Flow in the supercritical slope runs at a very fast velocity, and seldom deposits sediment in the steep channel. Meanwhile, most sediment is transported to the streams with flat hydraulic slopes. Due to the functioning of the reservoir, the transition region from supercritical slope to subcritical slope has a much larger probability of being submerged during the flood.

Polycyclic aromatic hydrocarbons (PAHs) in riparian soils of the middle reach of Huaihe River: A typical coal mining area in China

ABSTRACT In the present research work, the concentration, distribution, composition, sources, potential toxicity, and ecological risk of PAHs in riparian soils of the middle reach of Huaihe River (along a 430-kilometer stream gradient) were studied. The total concentrations of PAHs varied from 210 to 39000 ng g−1, with a mean concentration of 3400 ± 8400 ng g−1 and a median value of 760 ng g−1. The middle section (Huainan-Bengbu section) with frequent coal mining and utilization activities was found to be the most contaminated region. High molecular weight (5- and 6- ring PAHs) and medium molecular weight (4- ring PAHs) PAHs were predominant. Based on the diagnostic ratios method and positive matrix factorization (PMF) model, PAHs in riparian soils were mainly originated from pyrogenic sources including vehicle emissions, and biomass and coal combustion. The calculation of total TEQBaP concentrations and risk quotient (RQ) indicated a low to moderate risk level of PAHs in most regions of the study area, but some specific sites showing high toxicity and ecological risk should be caused alarm and attention.

Post-fire management effects on hillslope-stream sediment connectivity in a Mediterranean forest ecosystem

Forest fires intensify sediment transport and aggravate local and off-site consequences of soil erosion. This study evaluates the influence of post-fire measures on structural and functional sediment connectivity (SC) in five fire-affected Mediterranean catchments, which include 929 sub-catchments, by using the “aggregated index of connectivity” (AIC) at two temporal scenarios: I) immediately after the fire and before implementing post-fire practices (‘Pre-man’), and II) two years after the fire (‘Post-man’). The latter includes all the emergency stabilization practices, that are hillslope barriers, check-dams and afforestation. The stream system was set as the target of the computation (STR), to be representative of intense rainfall-runoff events with effective sediment delivery outside the catchments. Output normalization (AICN) allows comparing the results of the five basins between them. The sedimentological analysis is based on specific sediment yield (SSY) –measured at the check-dams installed after the fire –, and this data is used for output evaluation. Stream density and slope variables were the most influential factors on AICN-STR results at the sub-catchment scale. Post-fire hillslope treatments (barriers when built in high densities and afforestation) significantly reduced AICN-STR in comparison with untreated areas in both structural and functional approaches. Despite the presence of hillslope treatments, the higher erosive rainfall conditions resulted in higher AICN-STR values in the Post-man scenario (functional approach). A positive and good correlation was found between the measured SSY and the AICN-STR changes due to the post-fire practices and vegetation recovery, showing the good correspondence of the computation results and the real sediment dynamics of the studied catchments. Overall, AICN demonstrated to be a useful and versatile tool for post-fire management, which needs further research to optimize its applicability.

Distribution and carbon isotopic composition of long-chain leaf wax n-alkanes from Holocene lake sediments in the Altai Mountains

The Altai Mountains are located at the junction of Asia and Europe and pathways linking East Asian climate with the Arctic and North Atlantic. Here, we report a record of n-alkanes from the sediments of Shuanghu Lake in the Altai Mountains. In this forested region, the vegetation is dominated by C3 plants and the long-chain n-alkanes (C29–C31) in the lake sediments are predominantly derived from leaf wax lipids. The compound-specific carbon isotopic values of the long-chain n-alkanes are sensitive to regional moisture. Both the δ13C29–31 value and the Paq index show a decreasing trend since ∼9.0 kyr BP, implying an increase in moisture. This trend is punctuated by abrupt decreases in isotopic values centered at 8.2, 7.4, 5.6, 3.0, 2.0 and 0.2 kyr BP, which may indicate cold and wet events on decadal–centennial timescales. The Holocene hydrological patterns recorded at Shuanghu Lake are different from those from monsoonal Asia and they may reflect a response to decreasing Arctic sea ice cover that provided an enhanced moisture source and promoted increased heavy snowfall in the study region, or an increase in the temperature gradient and strength of the jet stream and extratropical cyclones at mid-latitudes, as proposed previously.

Tectonic Control of the Nanggulan Formation Based on Morphometric Analysis in Kulon Progo, Indonesia

DOI:10.17014/ijog.9.2.147-157Outcrop of Nanggulan Formation, surrounded by Old Andesite Formation (OAF) in the eastern part of Kulon Progo Dome, is very limited. Tectonic control is interpreted as a contributing factor. Tectonic activity can be shown by a morphometric aspect. The research purpose was to calculate the valley floor - valley height ratio, stream gradient index, and drainage density of Nanggulan and Old Andesite Formations. The method used is field survey and Shuttle Radar Topography Mission analysis. The field survey focused on Clumprit, Klepu, and Kalisonggo Rivers. The total number of valley segments for the Nanggulan Formation is 223 with the valley length of 4.62 km, while OAF is 101 with a valley length of 3.55 km. SRTM analysis showed that the valley segment in OAF was 55, and valley length was 1.48 km. The valley floor - valley height ratio measured in the Nanggulan Formation is ten valleys and OAF is eight valleys. In Nanggulan Formation, the valley floor - valley height ratio value is from 1.00 to 5.46 (low uplift), whilst in OAF, the results vary: as 1.35 to 4.58 (low uplift), 0.59 (medium uplift), and 0.43 (high uplift). The stream gradient index value of the Nanggulan Formation is 460.47 (medium tectonic), while OAF is 723.84 (high tectonic). The drainage density value of the Nanggulan Formation is 10.35 km/km2 (very smooth landscape texture) and OAF is 10.35 km/km2 (somewhat smooth landscape texture). Morphometry proves that Nanggulan Formation tectonic activity is more active, causing the Nanggulan Formation to be exposed to the surface.

Lithologic Controls on Geomorphic Evolution of the Central Western Ghats: An Example from the Aghnashini Catchment, Karnataka, India

Abstract In spite of the prolonged exposure and denudation (for >50 Ma), the catchments of the Western Ghats escarpment depict significant relief and rugged topography along the Indian passive margin. In this study, an endeavour has been made to comprehend the function of lithology in landscape dynamics of the Aghanashini catchment through quantitative geomorphology. Longitudinal profiles of this catchment demonstrate disequilibrium through anomalous high stream gradient index and normalized steepness index (ksn) that are related to topographic breaks. Correlation between lithology types and ksn inferred predominant lithologic control on drainage disequilibrium. Transformed coordinate (χ-plot) of the longitudinal profile explained the knickpoint dynamics in an extensive manner where the outcomes suggested river capture process, formation of steep gorge, and series of hanging waterfalls due to sudden change in boundary conditions. This study indicates strong lithologic control under the influence of intense precipitation on shifting knickpoints throughout the catchment area forcing to maintain the valley relief and hillslope angles responsible for rugged and high relief topography of Aghnashini catchment of the Western Ghats.

Classifying freshwater salinity regimes in central and western U.S. streams and rivers

AbstractFreshwater salinization of rivers is occurring across the globe because of nonpoint source loading of salts from anthropogenic activities such as agriculture, urbanization, and resource extraction that accelerate weathering and release salts. Multidecadal trends in river salinity are well characterized, yet our understanding of annual regimes of salinity in rivers draining diverse central and western U.S. landscapes and their associated catchment attributes is limited. We classified annual salinity regimes in 242 stream locations through dynamic time warping and fuzzy c‐medoids clustering of salinity time series. We found two dominant regimes in salinity characterized by an annual summer–fall peak or spring decline. Using random forest regression, we found that precipitation amount, stream slope, and soil salinity were the most important predictors of salinity regime classification. Advancing our understanding of salinity regimes in rivers will improve our ability to predict and mitigate the effects of salinization in freshwater ecosystems through management interventions.

Sedimentation in East Coast Hilly Terrain Reservoirs; Balimela, Odisha

Globally reservoirs behind dams are changing their hydrologic cycle under a shifting climate. Sediment, the flagship for water resources projects provide negative impact on environment and dam benefits. Sedimentation behind dams is continuous, regular through sequential paths that comprises of erosion, entrainment, transference from upper basin and deposition within the reservoirs. Present study envisages the morphometric study of the Balimela Reservoir active from 1972. The downloading of Geographic Information System (GIS), Remote sensing (RS) data from LANDSATS and making Stream order, Contour, slope and aspect maps by constructing Digital Elevation Model using the various Arc-GIS tools. The average bifurcation ratio is safe.. Considering the water-spread areas at various elevations of the years 2000, 2002, 2013, 2016, 2019 and 2022, the sediment deposits and reduction of storage volume by 29.945% by Jan 2022 since first impounding. The dam housed in hilly terrains, so there is less increase of catchment erosion except deforestation. The water from the dam optimally used by both the states Odisha and Andhra Pradesh. Preparation and strict adherence of concrete reservoir operation rule, upstream proper upstream maintenance and best catchment treatment plans shall increase the dam’s longevity and utilities.

How Socio-Economic Drivers Explain Landscape Soil Erosion Regulation Services in Polish Catchments.

Most studies that address the relationship between socio-economic characteristics and soil erosion focus on the effects of soil erosion on socio-economic conditions at different levels, from global to smallholder. Few, if any, efforts are made to address the influence of socio-economic variables on the soil erosion rate as an indicator of landscape degradation. The present study was carried out using spatial data from 402 catchments that cover Poland, to find out how socio-economic variables, which include area-weighted average income per capita (PLN km−2), area-weighted average gross domestic product (PLN km−2), population density (person km−2), and human development index can drive the soil erosion rate (kg ha−1 yr−1), along with annual precipitation, soil and geomorphological variables that include soil organic carbon content, soil water content, clay ratio, stream gradient, and terrain slope. The results showed that the soil erosion rate is indirectly driven by the socio-economic variables in the study catchments, as it is alleviated by increasing population density, the area-weighted average gross domestic product, and the human development index. Furthermore, analyzing the incremental relationship between soil erosion rate and the area-weighted average of socio-economic variables revealed that no uniform change can be observed in the relationship between the area-weighted average socio-economic variables and soil erosion in the study catchments.

Classification and Assessment Methods for Mountain Channel Habitats in the Chishui River Basin, China

Mountain channels have received relatively little study compared to lowland rivers due to their complicated fluvial geomorphology and inconvenient traffic. Classification schemes and habitat assessments in mountain channels should be strengthened to provide a scientific basis for river ecological restoration. Therefore, we tried to simplify the habitat assessment of mountain channels using a suitable habitat classification scheme based on high-resolution satellite imagery. We used China’s Chishui River basin because it is a typical mountain river system. Five parameters (stream order, elevation, slope, sinuosity and river network density) and 120 sites were used for habitat classification. In addition, we recorded 20 metrics in four categories (water environmental status, river morphology, riparian zone and human disturbance). Our results identified a total of 40 representative sampling sections belonging to six habitat types that were useful for habitat assessment across the Chishui River basin. The basin was given a mean comprehensive habitat quality index (CHQI) score of 130.66 ± 24.14 and classified under the status “good.” However, the headwaters, Tongmin River, Tongzi River and Xishui River were disturbed by various human activities. We conclude that the process of developing and simplifying our habitat assessment systems can be regarded as a reference for biomonitoring in other mountain river systems.

Quantifying spatial and temporal relationships between diatoms and nutrients in streams strengthens evidence of nutrient effects from monitoring data.

Observational data are frequently used to better understand the effects of changes in P and N on stream biota, but nutrient gradients in streams are usually associated with gradients in other environmental factors, a phenomenon that complicates efforts to accurately estimate the effects of nutrients. Here, we propose a new approach for analyzing observational data in which we compare the effects of changes in nutrient concentrations in time within individual sites and in space among many sites. Covarying relationships between other, potentially confounding environmental factors and nutrient concentrations are unlikely to be the same in both time and space, and, therefore, estimated effects of nutrients that are similar in time and space are more likely to be accurate. We applied this approach to diatom rbcL metabarcoding data collected from streams in the East Fork of the Little Miami River watershed, Ohio, USA. Changes in diatom assemblage composition were consistently associated with changes in the concentration of total reactive P in both time and space. In contrast, despite being associated with spatial differences in ammonia and urea concentrations, diatom assemblage composition was not associated with temporal changes in these nitrogen species. We suggest that the results of this analysis provide evidence of a causal effect of increased P on diatom assemblage composition. We further analyzed the effects of temporal variability in measurements of total reactive P and found that averaging periods greater than ~1 wk prior to sampling best represented the effects of P on the diatom assemblage. Comparisons of biological responses in space and time can sharpen insights beyond those that are based on analyses conducted on only 1 of the 2 dimensions.

Plio-Pleistocene paleodrainage reconstruction using moldavite-bearing and morphostratigraphically related deposits (Southern Bohemia, Czech Republic)

The area of Southern Bohemia between Novohradské hory Mountains and the Třeboň and Budějovice Basins – the Novohradské Foothills (in the south of the Czech Republic) is known for the occurrence of moldavites. These tektites are abundant in fluvial Koroseky sands and gravels. This study focuses on reconstructing the paleostreams, which deposited the moldavite-bearing sediments, and their relationship to present streams. Based on a review of the deposits' occurrences, a connection between moldavite-bearing sediments and deposits of the present watercourses, Vltava, Malše, Stropnice and Svinenský, is proposed. The link between moldavite-bearing deposits and the current streams were further supported by analyses of river geometry (longitudinal profiles, stream gradient) and terrain morphology (valley floor ratio, basin asymmetry). It is suggested that the moldavite-bearing deposits were sedimented during the Pliocene or Pleistocene by predecessors of the present streams. The occurrences of particular fluvial deposits and changes in terrain morphology and river geometry can be traces of changes in the river network and the dynamic evolution of local relief induced by tectonic activity during the Pliocene and Pleistocene.

Tectonogeomorphic investigation of Kashmir Basin NW Himalaya

ABSTRACT The present study has been carried out in Kashmir Basin (KB), NW Himalaya, to determine the relative tectonic activity using morphotectonic analysis, drainage patterns, lineament analysis and geomorphological field observations. Geomorphic signatures in KB indicate that intrabasinal faults have been quite active during the Quaternary time and have played a dominant role in kinematic and structural evolution of the basin. The manifestation of this activity has been recorded by terrain morphology, uplifted river terraces, warped fluvial surfaces, strath surfaces, fault scarps, offset of Holocene sedimentary successions, braided, and offsetted drainage patterns and recent seismic activity in the region. Presence of active mountain fronts; concave, convex, and concavo-convex hypsometric curves; ambiguous stream gradient index and drainage basin asymmetry, elongated sub-basins clearly manifest tectonic influences in sculpting the basin geometry. The presence of NW-SE to NNE-SSW lineaments that generally strike parallel with the major regional tectonic structures (faults) clearly suggest intense deformation zones produced by ongoing regional tectonism. We propose that the techniques employed, the data obtained and the technical interpretations, are potentially useful and may also be extrapolated to similar tectonically active regions.

Prediction of Manning's coefficient of roughness for high-gradient streams using M5P

Abstract The coefficient of Manning's roughness (n) has been generally implemented in the determination of depth and discharge in open channels and canals. This study unravels the novel idea and potential of Random Forest (RF), M5P, and Random Tree (RT) approaches to evaluate and predict the coefficient of Manning's roughness for hydraulic designing. To achieve this purpose, 42 observations were collected for high-gradient streams in Colorado, USA. All the observations were from boulder-bed, cobble and high gradient (S > 0.002 m/m) streams within bank flows. In order to ascertain the best model, the above-mentioned approaches were evaluated and compared using performance evaluation indices such as mean absolute error (MAE), coefficient of correlation (CC), and root mean square error (RMSE). Outcomes of performance evaluation indices revealed that the proposed pruned M5P approach outperformed other applied models for predicting the coefficient of Manning's roughness for hydraulic designing with CC = 0.7858, 0.7910, RMSE = 0.0195, 0.0195, and MAE = 0.0157, 0.0165 for model development and validation period, correspondingly. Furthermore, Taylor diagram and Box plot also suggest that the M5P based approach works better than RF and RT based approaches for predicting the coefficient of Manning's roughness for high-gradient streams using the given data set.

Large-scale assessment of spatial variability in stream power distribution: An indicator of channel erosion and deposition potential

Channel morphodynamics, governed by erosion and deposition processes, constitute a relevant aspect of integrated water management planning, and development of sustainable fluvial projects. According to the Water Framework Directive, there is a need for hydromorphological recognition and channel geomorphic adjustment at the national level. Such a large scale excludes field measurements as the primary research method. Instead, methods that require less resources and are based on relatively simple process representations are required. The stream power (SP) concept, combining the effect of channel gradient and discharge, has been widely used for quantitative measurements in geomorphic works at different spatial scales, but not at the national level so far. The primary objective of this study was to estimate total and specific stream power, and detect erosion and deposition patterns along the river network in Poland. Given the dominant role of stream slope in SP spatial variations, the specific objective was to assess the vertical accuracy of high-resolution DEM representing water surface elevations along the river course, and to propose a method for extraction of elevation points along river reaches that increase the accuracy of DEM-derived stream slopes. We demonstrated that DEM generally overestimates the elevation by more than 0.5 m, significantly affecting the DEM-derived stream slope estimation. By extracting minimum water surface elevation from DEM within a 15 m radius from the target cell (river segment endpoint), a substantial improvement was achieved. The difference between the actual and DEM-derived water surface elevation dropped to 0.16 m. The results indicated that the distribution of dominating processes in Polish rivers is strongly governed by the character and origin of the terrain relief and lithological diversity. For regions with flat relief, most channels are generally in the state of equilibrium, whereas in upland and mountainous regions, erosion processes are dominant. This study demonstrates the potential use of the SP concept for mapping channel sensitivity to erosion and deposition dominance at a national scale, which can be relevant for integrated river catchment management.

Evolution of Surface Drainage Network for Spoil Heaps under Simulated Rainfall

Spoil heaps laid from the infrastructure building sites or the mining sites are confoundedly prone to accelerated soil erosion and inducing debris flows on extreme rainfall occasion, thus threatening water quality and personal safety. In present study, the roughness and drainage network evolution of the loess spoil heap (a 33° slope gradient) were investigated via indoor simulation experiment under three rainfall intensities (60, 90, and 120 mm/h). A detailed scan of the slope using laser scanner, topographic analysis based on ArcGIS software, and statistical analyses were the main methods utilized in the study. The results showed that surface roughness increased with cumulative rainfall. For three rainfall intensity treatments, the proneness of shallow landslide under 90 mm/h intensity resulted in the largest roughness. The drainage density and stream frequency of the spoil heap slope both decreased with cumulative rainfall and negatively correlated with surface roughness, which indicated the convergence of the drainage network. Meanwhile, the individual flow paths presented an increasing sinuosity and a decreasing gradient with cumulative rainfall. However, drainage network features varied in a less marked degree during different rainfall intensities, showing comparable fractal dimensions of 1.350–1.454, 1.305–1.459, and 1.292–1.455 for the three rainfall intensities. Evaluating the response of four hydrodynamic characteristics of runoff to the drainage network evolution, stream power was found to be most sensitive. The linearity of the relationships between stream power and drainage density and that between stream sinuosity and gradient were estimated to have R2 between 0.961 and 0.979.

Key Drivers Influencing the Presence and Absence of Micropterus salmoides and Their Effect on Native Fish Communities and Biotic Integrity

Invasive alien fish species (IAFS) influence recipient ecosystems in multiple ways, from altered native fish communities to poor ecological health and higher economic losses to control and eradication. We tested key drivers and connections between an IAFS (Micropterus salmoides) presence, absence, geomorphological, hydro-chemical, physical habitat, native fish assemblages, and large river basins biotic integrity during 2016–2019. A total number of 62,121 individuals (TNI) representing 74 fish species were observed, out of which 68 species (45,677 TNI) belonged to the Geum River (GR) basin, while 63 species (16,444 TNI) were from the Mankyong/Dongjin River (MDR) basin. The results illustrated a significant contrast based on stream order, catchment area, altitude, stream gradient, and width among the sites with and without largemouth bass. However, fluctuations in nutrients (nitrogen and phosphorus) were not affected by variations in pH, dissolved oxygen, conductivity, suspended solids, and river flow. The largemouth bass has emerged as the 8th largest fish population in the GR and swiftly occupies the MDR basin with a constancy value of 45.5. Native sensitive (r = −0.38), insectivore (r = −0.252), carnivores (r = −0.085), and TNI (r = −0.512) displayed a negative correlation with increasing largemouth bass abundance. Largemouth bass induced significant regime transformation in the carnivore species. A significant difference (p < 0.01) of biotic integrity was illustrated among the largemouth bass population sites. A conspicuous interplay between ‘poor’ ecological health (r = 0.33, p = 0.038, n = 41) sites and ‘fair–excellent’ (r = −0.38, p < 0.001, n = 622) sites as compared to the overall ecological health linked with largemouth bass abundance (r = −0.397, p < 0.001, n = 663) alluded to stronger impact of the IAFS. In conclusion, the largemouth bass has potentially altered the native fish assemblage and ecological health. Further, we conclude that rapidly shifting flow patterns supported by the expanding anthropogenic interventions (weirs and dam) are the most approving factors of impending fish invasions.

Comparison of annual maximum and peaks-over-threshold methods with automated threshold selection in flood frequency analysis: a case study for Australia

Flood frequency analysis (FFA) involves fitting of a probability distribution to observed flood data. Two main models, annual maximum (AM) and peaks over threshold (POT), are generally adopted in FFA. The POT model is underemployed due to its complexity and uncertainty associated with threshold selection and meeting independence criteria in selecting POT data series. This study evaluates the POT and AM models using data from 188 gauged stations in southeast Australia. The POT model adopted in this study applies different average numbers of events per year fitted with generalized Pareto (GP) distribution with an automated threshold detection method. For the AM model, the GP distribution is also adopted, and flood quantiles estimated by the two models are compared. It has been found that there are notable differences in design flood estimates between the AM and POT models. The study uses catchment characteristics data to understand the differences in quantile estimates between the AM and POT models. The percentage differences between the AM and POT models can be explained by mean annual rainfall (MAR) and mean annual evapotranspiration (MAE) (ARIs of 1.01–5 years), MAR (10-year ARI), stream density (SDEN) (for 20- and 50-year ARIs) and SDEN, main stream slope (S1085) and MAE (for 100-year ARI). Stations showing smaller % differences have relatively higher MAR and smaller MAE (indicating wetter condition); conversely, stations showing higher % differences have smaller MAR and higher MAE (drier condition).