ABSTRACT Global change‐induced lake water scarcity highlights the urgent need for targeted ecological flow restoration, but such restoration conflicts with lake flood regulation and undermines the performance of existing projects. Taking Dongting Lake as the study case, this study develops an integrated flow restoration strategy that systematically reconciles water replenishment demands and flood control requirements. The strategy is developed based on long‐term time‐series hydrological station observations and riverbed topographic datasets, leveraging generalized hydrological model simulations and machine learning algorithms. The results reveal that from 1955 to 2020, the runoff from the Yangtze River into Dongting Lake experienced a significant decline of 32.71%, which has become the dominant driver of the lake's water resource depletion. The average maximum flow rate of the “Three Channels” has decreased by about 729 m 3 /s over the years, while the annual interruption rate has significantly increased. Through scenario‐based river regulation simulations, this study demonstrates that targeted riverbed elevation lowering by 1.5 m at Shadaoguan, 1.0 m at Mituo Temple, and 0.5 m at Guanjiaopu can effectively maintain the synergistic balance between water resource supply security and flood control functional integrity. The proposed framework provides a replicable methodological reference for the ecological restoration of river–lake connected water systems, offering a viable solution to reconcile the long‐standing conflicting demands in water replenishment practices.
ABSTRACT We propose an integrated geomorphic framework for floodplain zoning along a 140 km stretch of the Narmada River, India (between Bargi Dam and Barmanghat). This framework utilizes Sentinel‐2 multispectral images (10 m), Copernicus Forest and Building‐Free DEM (FABDEM), and topographic profiles measured in the field using Differential GPS (DGPS). Following Central Water Commission (India) guidelines, we classified the floodplain into three zones. These include the No‐Go Zone (NGZ; 2–5‐year return period), Regulatory Zone (RZ; 25‐year return period), and Warning Zone (WZ; 100‐year return period). We delineated these zones entirely based on geomorphic features, topographic breaks, and riparian vegetation. The NGZ includes hydrologically connected depressions, swamps, and bank‐intact gullies with water‐tolerant riparian vegetation. The RZ comprises flood channels, large depressions, crevasse splays, and wetlands with lush woody vegetation. The WZ encompasses elevated terraces, paleochannels, and ravines with wide‐canopy, trunk‐root trees. We performed field validation through reconnaissance, local surveys, RTK‐DGPS surveys (< 2 cm vertical accuracy), and drone images (1–2 cm resolution). To assess this holistic geomorphological approach, a 1D HEC‐RAS model was set up for comparison along a 70‐km sub‐reach (Bhedaghat–Barmanghat). We merged the channel bathymetry measured using an Acoustic Doppler Current Profiler (ADCP) and FABDEM for the true representation of channel geometry into the model. We calibrated and validated the model using water‐level data recorded from 1977–2023 at a gauge station near Belkhedi. This model yielded an RMSE of 1.25 m and . Comparing the floodplain zonation obtained from geomorphic approach to the model, we found the value of Intersection‐over‐Union (IoU) for NGZ = 0.53, RZ = 0.42, and WZ = 0.31. The NGZ area demonstrates a consistently close agreement between the two approaches. However, flow regulation and anthropogenic modifications significantly decoupled the RZ and WZ in contemporary hydraulic inundation patterns. Hydraulic models underestimated the flood extents of the RZ and WZ due to dynamic terrain changes. Geomorphic analysis and local surveys enabled us to refine these flood zone boundaries by identifying land‐use impacts. These landform alterations lead to rapid flood pattern changes observed in the field survey. The geomorphic component does not rely on discharge data; we believe that the geomorphic framework directly applies to managing flood risk in ungauged or data‐scarce river corridors. The geomorphological zonation provides a scientific foundation of first‐order functional classification of floodplains for long‐term river corridor planning.
Centuries of river modification, particularly straightening and incision, have severely reduced lateral connectivity between rivers and their floodplains. As a result, Stage 0 riverscapes, characterised by high lateral connectivity (e.g., anastomosing or wetland riverscapes), are now rare in anthropogenic landscapes. Restoration to a Stage 0 condition is gaining international momentum but remains relatively untested, particularly in human-modified landscapes with novel constraints and challenges. Here, we provide a perspective on lessons learnt from restoration to Stage 0 in anthropogenically constrained settings. We draw on experience from the design, construction, and monitoring of two UK restoration projects, among the first valley-floor reset rivers in Europe: the River Aller and the River Witham. Through infilling incised channels and regrading the floodplain, valley-floor reset transformed the single-thread, incised channels into multi-thread, river- wetlandscapes and substantially increased river-floodplain connectivity. In response, the water table elevation rose by about 1 m and baseflow wetted width increased by 9- to 20-fold; for example, average baseflow wetted width at the Aller increased from 4 to 81 m (maximum baseflow width increased from 7 to 147 m). We summarise six lessons learnt: (1) Restoring dynamic riverscapes means embracing uncertainty and navigating societal expectations, (2) Stage 0 and valley-floor reset are not appropriate everywhere: informed restoration is required, (3) Space exists for restoring river lateral connectivity, even in anthropogenically-constrained catchments, (4) Interrupting long-profile connectivity with grade-control structures needs careful design, (5) Restoring lateral connectivity creates multi-functional landscapes for water, wildlife and people, and (6) Structured, transdisciplinary research is needed to align restoration of natural processes with societal needs in a changing climate, and unlock the potential of river lateral connectivity to enhance biodiversity, river ecosystem services and climate resilience.
Anthropogenic impacts on the thermal regime of rivers include climate change and deforestation. For the latter, developing modelling tools that can account for the impact of varying vegetation cover on river temperatures is essential. This study describes a new addition to the CEQUEAU hydrological and water temperature model: a shading algorithm. This relatively simple tool accounts for vegetation height, stream orientation and the associated shadow length on the river to modulate incoming solar shortwave radiation. The algorithm was tested on seven different sites from five Canadian rivers. The results indicate that the algorithm either maintained or slightly improved model performance. Different deforestation and afforestation scenarios were tested and the model showed sensitivity to changes in riparian vegetation height, as a function of width and initial vegetation cover.
Sediments are avoided in many river and dam managements because of their adverse effects on water usage and flood control. Recently, sedimentation control measures, including sluicing, have been employed to manage sediments in river channels and restore communities in dammed rivers. Sediment sluicing is a technique used to control sedimentation in reservoirs by allowing sediment-laden water to pass through dams during high-flow events by establishing lotic conditions. Although sluicing operations can provide sediment and increase community diversity in river channels below dams, their effects on reservoir fauna remain unclear. Therefore, this study aimed to investigate the effects of sluicing operations on fish and benthic invertebrate communities in two reservoirs using 14-year monitoring data. Our results showed significant increases in total nitrate in water and oxidation-reduction potential at the bottom, decreases in suspended solids in winter, and reductions in taxon richness and total density of summer macroinvertebrate communities after sluicing operations. However, the results suggested that the population of macroinvertebrates and fish recovered over time after each dam operation. In conclusion, although sluicing operations reduced reservoir biota, macroinvertebrate and fish richness were restored within a few months after the operation, suggesting that the impact of dam operations on biota may be minimal.
