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• The runoff, sediment load and runoff erosion power decreased significantly. • Compared with runoff, runoff erosion power-sediment relationship is better. • The power function of runoff erosion power and sediment is better than linear. • Erosion in particular geographic locations responds strongly to runoff erosion power. In recent years, the acceleration of urbanization in the Yangtze River Economic Belt (YREB) has brought about problems such as soil erosion, ecosystem degradation and decline in ecological service functions. Therefore, this paper selects the Fujiang River Basin (FRB) in Upper Yangtze River (UYR), and analyzes the relationship between runoff erosion power (REP) and sediment transport (ST) on the basis of analyzing the variation characteristics of hydrological elements. Based on SWAT model, a variety of scenarios are set up to quantitatively analyze the impact of different land use changes on runoff and ST and REP in the basin. The results indicated that: (1) The annual precipitation in FRB from 1960 to 2018 did not change significantly, while the annual runoff, annual ST and annual REP decreased significantly. Compared with runoff and runoff depth, the relationship between sediment transport modulus (STM) and REP is the best, especially the power function between them is better than the linear function. (2) The results of the evaluation indexes of the simulation results of the SWAT model based on the measured runoff and sediment data from 2008 to 2018 are pass and above, that is, the simulation results are considered reliable. (3) Under the five scenarios of conversion of sloping farmland to forest, conversion of dry land to paddy field and conversion of grassland to bushland and forest land, the runoff and ST in the basin decreased but the overall range was small. The simulation results of SWAT model show that the erosion of specific areas in the basin shows the greatest degree of weakening with the decrease of REP. [ABSTRACT FROM AUTHOR]

Abstract Instream wood in steep headwater streams impacts channel morphology and sediment fluxes via the development of log steps and related sediment storage. I investigated detailed characteristics of 73 log steps in managed temperate Carpathian forests and assessed channel- and wood-based thresholds for log step development. The limited recruitment of wood from managed forests was apparent in the low frequency of log steps (an average of 1.3 steps per 100 m channel length) in bedload-dominated channels when compared to temperate and boreal old-growth forests, and an even lower number of log steps was observed in streams recently affected by debris flows or hyperconcentrated flows. The upstream threshold of log step occurrence can be assigned to those locations in stream longitudinal profiles, where transport capacity during ordinary high flows exceeds the critical value for the initiation of bedload movement. Downstream thresholds are controlled by stream transport capacity and wood dimensions, which correspond to the limited recruitment of large wood pieces in managed forests. All log steps were found in contributing basin areas smaller than 1 km2, and the majority of log steps (93.1%) originated in channels less than two metres in width. The development of a log step at a particular channel width or basin area was controlled by the wood length, but the resultant step parameters (step height and width, length of upstream sedimentary wedge and volume of stored sediments) were better correlated with wood diameter. The parameters of horizontal and vertical wood orientation had less importance in the development of a log step or its dimensions. Wood pieces shorter than 4 m in length accounted for 72.2% of the step-forming pieces, and the maximal diameter was less than 0.1 m for 20.5% of the pieces. These findings show the significance of relatively small wood pieces in log step development and sediment routing in steep headwater streams; the average sediment storage generated by a log step was 0.51 m3. The support of log step development and their preservation in headwater streams draining managed forests represents an alternative low-cost approach for sediment management at the basin scale. [ABSTRACT FROM AUTHOR]

• We couple P(C) and RUSLE to simulate erosion and sediment connectivity. • The model is applied to steep, forested and reclaimed mine landuses. • Connectivity and soil loss on reclaimed mine lands are greater than forested lands. • Disconnectivity occurs due to legacy terraces and soil texture. • Feedback calibration schemes resolve codependency of models. Coupling erosion formulae with sediment connectivity methods is one promising approach to better represent structural and functional variability of sediment processes. To advance this goal, the probability of connectivity approach is coupled with the revised universal soil loss equation (RUSLE) in a basin with forest and reclaimed mine landuses. Model evaluation showed unforeseen codependency between connectivity formulae and RUSLE. For example, the RUSLE P factor was codependent with the probability of downstream transport within the connectivity formula. Researchers should use feedback calibration schemes to resolve lack of model independence. Connectivity modelling advanced prediction of sediment processes because it simulated the unforeseen impact of legacy terracing on sediment connectivity and soil loss. Structural control dominates connectivity in this study, and soil loss and connectivity are self-similar. The structural control is contrary to recent suggestions that functional, dynamic processes control sediment connectivity in all landscapes. Self-similarity also remains an open topic because a number of studies show poor correlation between soil loss and connectivity. On average 12% of forested land and 47% of reclaimed mine land was connected for events studied. Predicted soil loss rates in the reclaimed mine were approximately 30 times greater than the forest land despite the fact that the reclamation is classified as phase 3. Spatially explicit results highlight pathways that should be targeted for remediation, and this study supports the idea of the Forestry Reclamation Approach for remediation of excess soil loss. [ABSTRACT FROM AUTHOR]

• We have developed modeling framework in a Loosely Coupled System. • The hydrologic cycle components are modelled using Soil and Water Assessment Tool. • Land use conversion due to human action is developed using Agent-based Modeling framework. • Climate change scenarios predict higher streamflow. • Combined climate and land use change scenarios project to reduce sediment load. Climate and land use change are the two primary factors that affect different components of hydrological cycle as well as sediment transport in the watershed. Quantifying potential impact of these two stressors enables decision makers to formulate better water resource management strategies to adapt to the changing environment. To that end, we have developed an integrated modeling framework employing an Agent-based approach to simulate land use conversion that then serves as input to the Soil and Water Assessment tool (SWAT) in a loosely coupled fashion. The modeling framework was tested on the Neshanic River Watershed (NRW), 142 km2 area in central New Jersey that contains mix of urban, agricultural and forested lands. An ensemble of 10 different global climate models (GCMs) for two different greenhouse gas emission scenarios including representative concentration pathways-4.5 and 8.5 (RCP-4.5 and 8.5) were employed to model future climate from 2020 to 2045. Land use conversion for 2040 was developed based on six driving factors including distance to residential lands, agricultural lands, roads, streams, train stations, and forest using three land use transition potential models and further, the best transition potential model accompanied with some local land use restrictions. The study evaluated various components of hydrological cycle and sediment transport for the three different scenarios one-at-a-time including climate change alone, land use change alone, and combined climate and land use change. Results indicate that the changing climate will have a larger effect on the hydrologic cycle than intensifying urban land uses in the study watershed. The climate change scenarios, either alone or in composite with land use change, predict higher streamflow (32% and 36% increase over baseline, respectively), overriding the effect of land use change which predicts a decline of 5% in streamflow. The increase in streamflow results in an increase in sediment loading, presumably due to an increase stream downcutting. Conversely, the effect of land use change (in this case the conversion of agricultural land to low density residential uses), is predicted to decrease sediment load. When modelled in composite, the effect of changing land use (in this case the conversion of erodible agricultural fields to suburban development) appears to override the adverse effect of climate change, enhancing watershed resiliency by reducing sediment load and thereby improving health of the downstream aquatic ecosystems. [ABSTRACT FROM AUTHOR]