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Extreme weather patterns and unsustainable development dynamics have substantially increased disaster risks compelling widespread demand for community resilience worldwide. This study aims to develop and measure Risk-integrated Resilience (RiR) index of flood-affected downstream communities in West Rapti Basin (WRB) of the Nepal Himalaya. The evidence-based RiR framework being developed here links risk factor with capital-based resilience characteristics. Three levels of risk zones were categorized based on the flood inundation level considering the latest highest river discharge (7643 m3/s) that the community experienced in 2014. The low-risk zone (≤ 1 foot), moderate-risk zone (> 1 foot to < 5 feet) and high-risk zone (≥ 5 feet) were integrated with five capital domains of resilience characteristics: human, social, economic, physical and natural. Data were acquired through the questionnaire survey from 156 residents, and 61 indicators were finalized for the resilience assessment (r > 0.80; α = 0.85). Shannon entropy-based quantitative method was adopted to assign weight for each indicator. The resilience index was estimated in each capital domain, and finally the composite resilience index was determined in all three risk zones: low-risk zone = 0.358; moderate-risk zone = 0.365; and high-risk zone = 0.295. The result suggests that disaster risk reduction interventions in WRB should focus on improving the lower level of resilience, while low-risk zone should not be neglected. The study highlights that resilience assessment linking risk factors in basin scale is significant approach to reduce the negative impact of flood disasters. The new perspective, evidence-based RiR framework, value adds to effectively and efficiently address the disaster challenges in river basin scale. [ABSTRACT FROM AUTHOR]

Downstream hydraulic geometry (DHG) for multiple discharge frequencies remains poorly investigated. This paper seeks to clarify the DHG relations of different discharge frequencies and proposes the definition, mathematical expression, and geomorphological interpretation of multifrequency DHG (MFDHG). It also verifies the existence of DHG and MFDHG in the six major exoreic rivers located in the Qinghai–Tibet Plateau. MFDHG can be depicted with (1) log-linear plots between DHG coefficients and exponents for multiple discharge frequencies and (2) independent DHG curves intersecting near congruent discharge, width, depth, or velocity. The results show that rivers in the study area exhibit strong DHG relations. The variations in the DHG coefficients and exponents usually exhibit opposite trends with increasing discharge frequency. The MFDHG of a river reach is generally stronger than that of a river basin. Congruent hydraulics, as indices of geometric variability and hydraulic self-similarity, reflect consistent changes in hydraulic variables downstream. MFDHG is a novel geomorphic phenomenon that bridges spatiotemporal dimensions in HG systems and provides a basis for establishing an overall HG relationship. [ABSTRACT FROM AUTHOR]

Soil erosion and sediment transport play important roles in terrestrial landscape evolution and biogeochemical cycles of nutrients and contaminants. Although discharge is considered to be a controlling factor in sediment transport, its correlation with sediment concentration varies across the Yellow River basin (YRB) and is not fully understood. This paper provides analysis from gauges across the YRB covering a range of climates, topographic characteristics, and degrees of human intervention. Our results show that discharge control on sediment transport is dampened at gauges with large mean annual discharge, where sediment concentration becomes more and more stable. This emergent stationarity can be attributed to vegetation resistance. Our analysis shows that sediment concentration follows a bell shape with vegetation index (normalized difference vegetation index, NDVI) at an annual scale despite heterogeneity in climate and landscape. We obtain the counterintuitive result that, as mean annual discharge increases, the dominant control on sediment transport shifts from streamflow erosion to vegetation retardation in the YRB. [ABSTRACT FROM AUTHOR]

Abstract: The distributed basin model (DBM) has become one of the most effective tools in river basin studies. In order to overcome the efficiency bottleneck of DBM, an effective parallel-computing method, named temporal-spatial discretization method (TSDM), is proposed. In space, TSDM adopts the sub-basin partitioning manner to the river basin. Compared to the existing sub-basin-based parallel methods, more computable units can be supplied, organized and dispatched using TSDM. Through the characteristic of the temporal-spatial dual discretization, TSDM is capable of exploiting the river-basin parallelization degree to the maximum extent and obtaining higher computing performance. A mathematical formula assessing the maximum speedup ratio (MSR) of TSDM is provided as well. TSDM is independent of the implementation of any physical models and is preliminarily tested in the Lhasa River basin with 1-year rainfall-runoff process simulated. The MSR acquired in the existing traditional way is 7.98. Comparatively, the MSR using TSDM equals to 15.04 under the present limited computing resources, which appears to still have potential to keep increasing. The final results demonstrate the effectiveness and applicability of TSDM. [Copyright &y& Elsevier]

Abstract: River coding method for drainage networks plays an very important role in the physical simulation of river basins. In this study we developed a new river coding method named Multi-tree Coding Method (MCM), which has the following features: (1) it is established on a topological pattern reflecting the dendriform structure of drainage networks; (2) the multi-tree code can be effectively managed by the database to perform convenient topological search toward drainage networks using Structured Query Language (SQL); (3) the multi-tree code does not exhibit digital overflow problems in the computer, thus any resolution and scale drainage networks can easily be coded; and (4) it supports high-efficient search process. A river reach can be directly positioned in a drainage network under MCM, without the complex search process from all river reaches. This feature has great potential to improve the computational performance of basin models. We demonstrate here the efficiency and practicality of MCM by testing it in the Yalu Tsangpo river basin, Tibet. A drainage network with 140,745 digital reaches was extracted from the digital elevation model (DEM), and the multi-tree codes of all river reaches were obtained. [Copyright &y& Elsevier]

Abstract: Restricted computing power has become one of the primary factors obstructing advancement in basin simulations for majority of hydrological models. Parallel computing is one of the most available approaches to solve this problem. Using binary-tree theory, we present in this study a common parallel computing framework based on the message passing interface (MPI) protocol for modeling hydrological processes of river basins. A practical and dynamic spatial domain decomposition method, based on the binary-tree structure of the drainage network, is proposed. This framework is computationally efficient, and is independent of the type of physical models chosen. The framework is tested in the Chabagou river basin of China, where two years of runoff processes of the entire basin were simulated. Results demonstrate that the system may provide efficient computing performance. However, primarily because of the constraint of the binary-tree structure for drainage network, this study finds that unlimited enhancement of computing efficiency is impossible to realize. [Copyright &y& Elsevier]

The middle Yellow River basin is known for its extremely high rate of erosion and sedimentdelivery and for the dramatic decrease in sediment yield over the last 20-30 years. Asuspended sediment rating curve (SRC, assumed to be Qs = aQb) describes the relationshipbetween water discharge (Q) and suspended sediment discharge (Qs) in a river, and theserelationships and their spatial and temporal variations could be used to interpret and indicatethe effect of climate change and human activities on sediment yield. The purpose of thisstudy was to examine how parameter values characterizing SRC, i.e. the exponent(b) and coefficient (a), were related to river basin characteristics, and to find outhow these SRC parameters varied from a period of poor vegetation cover priorto 1970 to a period with much improved vegetation cover since 2000. The SRCparameters were firstly estimated with the least square technique using log-transformeddaily data for 70 hydrologic gauging stations in the middle Yellow River basin.Precipitation, temperature, flow duration (the percentage of the number of days with theflows above 25% of the mean discharge), flow peakedness (the ratio of averageannual peak discharges to the mean discharge), drainage area, basin relief, and thepercentage of area with a slope &#x003E; 15˚ were used to characterize each of the 70river basins. The exponent b for the middle Yellow River basin ranged from 1.5and 3.3 for the 70 stream gauging stations. Correlation analysis showed that thecoefficient a was mainly negatively correlated with the long-term mean Q, basinrelief, drainage area, the annual mean precipitation and temperature, while a waspositively correlated with the flow peakedness, and the exponent b was most stronglycorrelated with flow duration. The SRC exponent b has significantly decreased from theperiod before 1970 with poor vegetation cover to the period since 2000 with muchimproved vegetation cover, while the SRC coefficient a has not changed muchbetween the two contrasting periods, this indicated the erosive power of streams havedecreased generally in the middle Yellow River region since 2000. The impact ofhuman activities on SRC parameters needed to be analyzed for further research. [ABSTRACT FROM AUTHOR]

• Dry riverbeds make the CO 2 emissions from intermittent rivers in arid areas equally important as from perennial rivers. • Combination of hydrological modeling, remote sensing and in-situ measurements improve the river CO 2 emission estimation. • Flow duration and dry riverbed area should be considered in estimating CO 2 emissions from intermittent river systems. Intermittent rivers in semiarid and arid regions, constituting over half of the world's rivers, alternate the carbon cycle interactions among the biosphere, hydrosphere, and atmosphere. Inadequate quantification of flow duration and river water surface area, along with overlooked CO 2 emissions from dry riverbeds, result in notable inaccuracies in global carbon cycle assessments. High-resolution remote sensing images combined with intensive field measurements and hydrological modelling were used to estimate and extract the flow duration, river water surface area and dry riverbed area of Huangfuchuan, an intermittent river watershed that acts as a major tributary of the Yellow River in semiarid Northwest China. CO 2 emission rates and partial pressures in water and air across the watershed were in-situ measured. In 2018, the flow duration of Huangfuchuan increased from less than 5 days in the first-order tributary to 150 days in the sixth-order mainstream. River water surface area estimated by remote sensing extraction plus the hydrodynamic model simulation varied from 3.9 to 88.6 km2 under 5 %–95 % discharge frequencies. CO 2 emissions from the water-air interface and dry riverbed in 2018 were estimated at 582.3 × 103 and 355.2 × 103 ton, respectively. The estimated total annual emission (937.5 × 103 ton) aligns closely with the range of emissions (67.3 × 103–1377.2 × 103 ton) calculated for the water-air interface alone, derived using DEM river length and hydraulic geometry method. This similarity can be attributed to the overestimation of flow duration and flow velocity, as well as the over- or under-estimation of river water surface area and slope. The new method proposed in this study has large potential to be applied in estimating CO 2 emissions from data-scarce intermittent rivers located in mountainous regions and provides a standardized solution in the estimation of CO 2 emission. Results of this research reveal the spatiotemporal distribution of CO 2 emissions along an intermittent river system and highlight the substantial role of dry riverbed in carbon cycle. [Display omitted] [ABSTRACT FROM AUTHOR]

Event-based suspended sediment dynamics (ESSD) provides insights into soil erosion and sediment transport and signals of changing environments within catchments, but it is still poorly understood in the middle Yellow River basin (MYRB). This study focuses on the hysteresis relationship between suspended sediment concentration (SSC) and flow discharge (Q), interpreting the ESSD and its spatial variation. The datasets in the 1960s from 73 hydrologic gauging stations were analyzed as the baseline of the MYRB without experiencing significant climate change and human disturbances. The Q -SSC hysteresis loops were first analyzed in terms of their direction and shape, and the Lloyd et al.'s (2016a) hysteresis index (HI) was adopted to quantify the hysteresis characteristics. Two types of catchments have been identified across the MYRB in terms of the dominant hysteresis pattern and the sign of the HI value. The dominant loops of the Type A catchments are clockwise with positive HI values and located in the southernmost rock mountain regions; Type B appears elsewhere, i.e., in the softstone, aeolian, and loess regions, where most of the events present anticlockwise or complex loops with generally negative HI values. The HI follows an upward-concave parabolic curve with either mean annual precipitation (P m) or vegetation cover (NDVI). Two sets of thresholds are determined as P m or NDVI increases. At P m = 670 mm or NDVI = 0.74, a transition from Type B to Type A occurs as the HI value changes from negative to positive because the vegetation cover is too high to change the catchment from non-limited to limited supply. At P m = 490 mm or NDVI = 0.40, the negative HI value reaches its minimum, suggesting the maximum availability of sediment in Type B due to the change in the dominant factor of soil erosion from precipitation erosivity to erosion resistance of vegetation. This study highlights the overall dynamics of soil erosion and sediment transport in the MYRB, which helps prioritize watershed management measures on the Loess Plateau under a changing environment. • Sediment supply environment is identified across the middle Yellow River basin. • Hysteresis index follows an upward-concave parabola with precipitation or NDVI. • Two sets of thresholds of spatial variations in suspended dynamics are determined. [ABSTRACT FROM AUTHOR]

Runoff decrease triggered or exacerbated by human activities over the past decades on the Loess Plateau has been drawing nationwide concerns; quantifying human-induced runoff-altering factors is of great significance for decision-making on maintaining regional water, ecological and economic security. Sediment-trapping dams (STDs) construction and revegetation are the two major soil-water conservation practices regarded to have caused runoff reduction, while their hydrologic effects on the basin scale have not been separated quantitatively. In this study, we chose the Huangfuchuan River Basin as a case study area, and proposed a physically-based attribution framework with the ability to account for the hydrologic effects of STDs, revegetation, and climate change simultaneously and attribute runoff decrease of the basin among these factors. The model-based attribution results revealed that STDs construction caused a 45% (48%) runoff reduction from 1976 to 1988 to 1989–2000 (2001–2014) and revegetation was responsible for a 30% runoff decrease from 1976 to 1988 to 2001–2014, while the daily simulation implied that the hydrologic effect of revegetation affected daily runoff magnitudes more consistently than that of STDs. Our study demonstrates that STDs construction was the prime contributor to runoff decrease in the case study area and suggests that STDs should be taken into account in similar studies on the Loess Plateau in the future. [ABSTRACT FROM AUTHOR]

• Annual variations are more significant than inter-annual variations for AHG exponent. • Ice regimes significantly contribute to the seasonal changes of AHGs. • The stability of AHG increases with the increase of stream order and drainage area. To be able to precisely estimate discharges in un-gaged streams and reconstruct hydrological features in river systems, the temporal and spatial variations of at-a-station hydraulic geometry (AHG) and their impacting factors need to be detected. To this end, the Yalong River and Upper Jinsha River, which located in southeast Qinghai-Tibet Plateau, are selected as case study. This investigation explores quantitative data on the magnitude of spatial and temporal variations in AHGs over a period of 10 years for 38 mountain reaches with drainage areas ranging from 0.53 × 103 to 259.18 × 103 km2. Effects of ice regime and drainage area on AHG were discussed and the stability of AHG was analyzed. 42.1% of the reaches have flow velocity exponents that are greater than the river width and flow depth exponents combined. No significant spatial variation tendency is observed for AHG exponents while significant temporal variations are reported. Larger fluctuations are found for AHG exponents in annual variations compared with those in inter-annual variations. Ice regimes significantly contribute to the seasonal changes of AHGs. The relative differences of AHG coefficients (a , c , k) and exponents (b , f , m) with and without ice vary between −49.4 to 80.8% and −70.1% to 22.6%, respectively. Compared with no ice regime, the reaches with border ice and slush ice run have smaller exponents m and Froude Number and larger coefficients c and exponents f. Besides, coefficients a and exponents m increase while coefficients k and exponents b decrease with the increase of drainage area. However, coefficients c and exponents f exhibit no tendency with drainage area changes. AHG stabilities increase with the increased stream order and drainage area. Results of this study can enrich the AHG database for mountain rivers and provide a preliminary understanding of ice effects on AHG variations. [ABSTRACT FROM AUTHOR]