Downstream Channel Research Articles

Ecosystem responses to channel restoration decline with stream size in urban river networks.

Urban streams are often severely impaired due to channelization, high loads of nutrients and contaminants, and altered land cover in the watershed. Physical restoration of stream channels is widely used to offset the effects of urbanization on streams, with the goal of improving ecosystem structure and function. However, these efforts are rarely guided by strategic analysis of the factors that mediate the responsiveness of stream ecosystems to restoration. Given that ecological gradients from headwater streams to mainstem rivers are ubiquitous, we posited that location within a river network could mediate the benefits of channel restoration. We studied existing stream restorations in Milwaukee, Wisconsin, to determine (1) whether restorations improve ecosystem function (e.g., nutrient uptake, whole-stream metabolism) and (2) how ecosystem responses vary by position in the urban river network. We quantified a suite of physicochemical and biological metrics in six pairs of contiguous restored and concrete channel reaches, spanning gradients in baseflow discharge (19-196L/s) and river network position (i.e., headwater to mainstem). Hydrology differed dramatically between the restored and concrete reaches; water velocity was reduced 2- to 13-fold while water residence time was 50-5,000% greater in adjacent restored reaches. Restored reaches had shorter nutrient uptake lengths for ammonium, nitrate, and phosphate, as well as higher whole-stream metabolism. Furthermore, the majority of reaches were autotrophic (i.e., gross primary production>ecosystem respiration), which is not common in stream ecosystems. The difference in ecosystem functioning between restored and unrestored reaches was generally largest in headwaters and declined to equivalence in mainstem restorations. Our results suggest that headwater sites offer higher return on investment compared to larger downstream channels, where ecosystem responsiveness is low. If this pattern proves to be general, the scaling of ecosystem responses with river size could be integrated into planning guidelines for urban stream restorations to enhance the societal and ecological benefits of these expensive interventions.

GIS-Based Gully Erosion Susceptibility Mapping: A Comparison of Computational Ensemble Data Mining Models

Gully erosion destroys agricultural and domestic grazing land in many countries, especially those with arid and semi-arid climates and easily eroded rocks and soils. It also generates large amounts of sediment that can adversely impact downstream river channels. The main objective of this research is to accurately detect and predict areas prone to gully erosion. In this paper, we couple hybrid models of a commonly used base classifier (reduced pruning error tree, REPTree) with AdaBoost (AB), bagging (Bag), and random subspace (RS) algorithms to create gully erosion susceptibility maps for a sub-basin of the Shoor River watershed in northwestern Iran. We compare the performance of these models in terms of their ability to predict gully erosion and discuss their potential use in other arid and semi-arid areas. Our database comprises 242 gully erosion locations, which we randomly divided into training and testing sets with a ratio of 70/30. Based on expert knowledge and analysis of aerial photographs and satellite images, we selected 12 conditioning factors for gully erosion. We used multi-collinearity statistical techniques in the modeling process, and checked model performance using statistical indexes including precision, recall, F-measure, Matthew correlation coefficient (MCC), receiver operatic characteristic curve (ROC), precision–recall graph (PRC), Kappa, root mean square error (RMSE), relative absolute error (PRSE), mean absolute error (MAE), and relative absolute error (RAE). Results show that rainfall, elevation, and river density are the most important factors for gully erosion susceptibility mapping in the study area. All three hybrid models that we tested significantly enhanced and improved the predictive power of REPTree (AUC=0.800), but the RS-REPTree (AUC= 0.860) ensemble model outperformed the Bag-REPTree (AUC= 0.841) and the AB-REPTree (AUC= 0.805) models. We suggest that decision makers, planners, and environmental engineers employ the RS-REPTree hybrid model to better manage gully erosion-prone areas in Iran.

Soil erosion and sediment interception by check dams in a watershed for an extreme rainstorm on the Loess Plateau, China

The magnitude of soil erosion and sediment load reduction efficiency of check dams under extreme rainstorms is a long-standing concern. The current paper aims to use check dams to deduce the amount of soil erosion under extreme rainstorms in a watershed and to identify the difference in sediment interception efficiency of different types of check dams. Based on the sediment deposition at 12 check dams with 100% sediment interception efficiency and sub-catchment clustering by taking 12 dam-controlled catchments as clustering criteria, the amount of soil erosion resulting from an extreme rainstorm event on July 26, 2017 (named “7·26” extreme rainstorm) was estimated in the Chabagou watershed in the hill and gully region of the Loess Plateau. The differences in the sediment interception efficiency among the check dams in the watershed were analyzed according to field observations at 17 check dams. The results show that the average erosion intensity under the “7–26” extreme rainstorm was approximately 2.03 × 104 t/km2, which was 5 times that in the second largest erosive rainfall in 2017 (4.15 × 103 t/km2) and 11–384 times that for storms in 2018 (0.53 × 102 t/km2 - 1.81 × 103 t/km2). Under the “7–26” extreme rainstorm, the amount of soil erosion in the Chabagou watershed above the Caoping hydrological station was 4.20 × 106 t. The sediment interception efficiency of the check dams with drainage canals (including the destroyed check dams) and with drainage culverts was 6.48 and 39.49%, respectively. The total actual sediment amount trapped by the check dams was 1.11 × 106 t, accounting for 26.36% of the total amount of soil erosion. In contrast, 3.09 × 106 t of sediment were input to the downstream channel, and the sediment deposition in the channel was 2.23 × 106 t, accounting for 53.15% of the total amount of soil erosion. The amount of sediment transport at the hydrological station was 8.60 × 105 t. The Sediment Delivery Ratio (SDR) under the “7·26” extreme rainstorm was 0.21. The results indicated that the amount of soil erosion was huge, and the sediment interception efficiency of the check dams was greatly reduced under extreme rainstorms. It is necessary to strengthen the management and construction technology standards of check dams to improve the sediment interception efficiency and flood safety in the watershed.

Characterization of a gigabit transceiver for the ATLAS inner tracker pixel detector readout upgrade

We present a gigabit transceiver prototype Application Specific Integrated Circuit (ASIC), GBCR, for the ATLAS Inner Tracker (ITk) Pixel detector readout upgrade. GBCR is designed in a 65-nm CMOS technology and consists of four upstream receiver channels, a downstream transmitter channel, and an Inter-Integrated Circuit (I2C) slave. The upstream channels receive the data at 5.12 Gbps passing through 5-meter 34-American Wire Gauge (AWG) Twin-axial (Twinax) cables, equalize and retime them with a recovered clock, and then drive an optical transmitter. The downstream channel receives the data at 2.56 Gbps from an optical receiver and drives the cable as same as the upstream channels. The jitter of the upstream channel output is measured to be 35 ps (peak-peak) when the Clock-Data Recovery (CDR) module is turned on and the jitter of the downstream channel output after the cable is 138 ps (peak-peak). The power consumption of each upstream channel is 72 mW when the CDR module is turned on and the downstream channel consumes 27 mW. GBCR survives the total ionizing dose of 200 kGy.

Sediment transport of different particle size groups in the downstream channel after operation of the Three Gorges Project

三峡工程蓄水后“清水”下泄，坝下游河段将会长期处于严重不饱和状态，水流含沙量沿程恢复将会引起坝下游长距离冲刷，本文根据三峡工程蓄水前、后的实测资料分析了坝下游河道泥沙输移变化规律，探索不同粒径组沙量沿程恢复对河床冲刷的影响，得到以下结论：在蓄水初期d≤0.031 mm沙量恢复主要受河床补给与江湖入汇共同的影响，随着水库下泄该粒径组沙量递减，使得各站该粒径组年均输沙量均远小于蓄水前的水平，沙量恢复仍主要受河床补给与江湖入汇的影响，这是造成坝下游河道发生长距离冲刷的主要原因之一；在蓄水初期0.031 mm < d≤0.125 mm沙量恢复主要受河床补给的影响，但江湖入汇的影响较大，随着河床补给量逐渐减少，各站该粒径组年均输沙量均小于蓄水前的水平，沙量恢复仍主要受河床补给的影响，江湖入汇的影响逐渐减小，这也是坝下游河道发生长距离冲刷的主要原因之一；d>0.125 mm沙量恢复主要受河床补给的影响，蓄水初期该粒径组沙量在宜昌-监利河段沿程恢复速率较快，且在监利站达到蓄水前的水平，随着时间推移，在宜昌-监利河段沿程恢复且速率仍较快，在监利站达到最大值，其数值逐渐小于蓄水前的水平，这是造成坝下游河道冲刷重点集中在宜昌-监利河段的主要原因.;Sediment concentrations in the downstream would be unsaturated in a serious long-term after the operation of the Three Gorges Project, since sediment concentration recovery causes long distance erosion in middle reach of the Yangtze River. Based on the field data collected after the operation of the Three Gorges Project, the sediment transport patterns in middle reach of the Yangtze River was analyzed, and the influence of sediment recovery along the river bed with different particle size groups on river bed erosion was explored. Result showed that:the recovery of sand content of d ≤ 0.031 mm was mainly affected by the replenishment of riverbeds and the inflow of rivers and lakes in the early stage of water storage. With the decrease of the amount of sand with d ≤ 0.031 mm, the average annual sediment transport amount of that group at each station was much smaller than that before the water storage. Recovery was still mainly affected by riverbed recharge and inflow of rivers and lakes, which was one of the main causes of long-distance erosion in the downstream channel of the dam. In the early stage of water storage, the recovery of sand volume of 0.031 mm<d ≤ 0.125 mm was mainly affected by riverbed recharge, but the impact of rivers and lakes was significant. With the gradual reduction of riverbed recharge, the average annual sediment transport of the particle size 0.031 mm<d ≤ 0.125 mm at each station was lower than that before the water storage, and the sand recovery was still mainly affected by riverbed recharge. The influence of inflow from rivers and lakes is gradually reduced, though this is still one of the main reasons for the long-distance erosion of the river downstream of the dam. d>0.125 mm sand recovery was mainly affected by riverbed recharge, in the initial stage of water storage, the sand content of this particle size group was faster in the Yichang-Jianli section, and it reached the level before the water storage in Jianli Station. In the Yichang-Jianli section, the rate was still relatively fast as time passes, peaking at Jianli Station. The value was smaller than the level before the water storage. This was the main reason that the downstream river channel erosion was concentrated in the Yichang-Jianli River section.

Effect of change of channel width in the downstream of the check dam on controlling sedimentation in Mrica Reservoir

The increasing sedimentation of Mrica reservoir shows that the sedimentation control has not been effective. The sedimentation control has been made include the disposal of sediments that settle in the reservoir by dredging or flushing. However, the results are not optimal. This is caused by the large volume of sediment entering the reservoir each year. The controlling volume of sediment that goes into the reservoir has also been carried out by conducting a watershed conservation program and building a check dam in the upstream Mrica reservoir. However, the existing check dam is still less effective in controlling sediments, especially suspended load sediments, that are transported in the river. Therefore this study was carried out by adopting the sediment trap concept to deposit sediments that escaped from the check dam. This study simulated changes in the width of the downstream channel of the check dam by three variations using HEC-RAS. There was a width of 20%, 40%, and 60% wider than the initial width. The results showed the effect of changing the channel width on volume sediment deposited. Based on the results of the study, the change in width to wider than the initial width could increase the volume of sediment deposits.

Quantitative geomorphological constraints on the landform evolution of the current active boundary of the northeastern Tibetan Plateau

The Hexi Corridor lies along the northeastern margin of the Tibetan Plateau forming its northern boundary. The late Cenozoic tectonic and landscape evolution of this area are key to understanding the growth of the Tibetan Plateau. We investigate the river profile morphology of 36 drainage areas located on the southern flanks of the Heli Shan, which is the outermost range of the Hexi Corridor. Here, bedrock channels are segmented by steep downstream channels and upper segments with lower gradients. A synthesis of tectonics, climate, lithology, and river reorganization indicates that this area has experienced accelerated tectonic uplift. We constrain the response times for knickpoint evolution based on a knickpoint celerity model and reconstruct paleo-channel profiles. Combined with onset ages for the growth of the Qilian Shan (10 Ma) and Yumu Shan (4 Ma), we propose that the Hexi Corridor and Heli Shan were affected by the outward growth of the Tibetan Plateau at 0.6–2.1 Ma ago.

Water Allocation Using the Bankruptcy Model: A Case Study of the Missouri River

This research applies cooperative game theory—specifically, the bankruptcy model—to address conflicts arising from the scarcity of water resources shared by multiple agents. This case study addresses potential outcomes of five allocation rules applied to the apportionment of water between two agents in the Missouri River. Currently, there is no interstate compact to apportion Missouri River and frequent disputes between upstream and downstream states occur. Upstream states favor managing reservoir water levels to support reservoir recreation and downstream states want water for the downstream navigation channel. The five allocation rules studied are (1) Proportional Sharing, (2) Constrained Equal Awards, (3) Constrained Equal Losses, (4) Sequential Sharing based on Proportional Sharing, and (5) a proposed Modified Constrained Equal Awards rule. The results of the analysis of apportionment during four dry years in the 2000s show that the best approaches are the proposed Modified Constrained Equal Awards Rule and the Proportional Sharing Rule.

Hydrodynamic characteristics and channel morphodynamics at a large asymmetrical confluence with a high sediment-load main channel

Previous studies of confluences have concentrated mainly on confluences of small streams, confluences with simple geometric configurations, and confluences of curving rivers. However, the confluences of natural rivers, especially large confluences of high sediment-load rivers, generally have complex geometric confluent boundaries and various incoming flow and sedimentation conditions. In this study, several field measurements of the three-dimensional velocity components, water surface elevation, bed topography, and suspended sediment particle sizes reveal the complex hydrodynamic characteristics and bed morphology of the asymmetrical confluence of the high sediment-load Yellow River and its clear tributary, the Fen River. The results show that the water surface morphology of this confluence is elevated in the stagnation zone, mixing interface, and the opposite side of the tributary, whereas the converse is true at the downstream junction corner. The geomorphologic features of the bed show a small scour hole and a long narrow scour belt under conventional hydrological conditions, or a larger scour hole under hydraulic conditions when the value of the momentum flux ratio is much greater than one. In contrast to the confluences of small streams and curving rivers, this confluence does not exhibit continuous flow separation or helical motion, but has pronounced regions such as a stagnation zone, flow acceleration and deflection areas, a shear layer/mixing interface, and a flow recovery zone. The position and size of these regions vary with the momentum flux ratio. The particle size of suspended sediment at the confluence is normally distributed, and the changing sedimentation process corresponds to the scour and siltation state of the bed. In general, the particle size of the suspended sediment is small in the stagnation zone and the downstream channel near the tributary, but large in the acceleration zone and shear layer. These results are helpful to better understand the hydrodynamic and morphodynamics characteristics of confluences with complex geometric configurations and junction conditions.

STIM1 Thermosensitivity Defines the Optimal Preference Temperature for Warm Sensation in Mice

Mammals possess a remarkable ability to sense subtle temperature deviations from the thermoneutral skin temperature of ~33 °C, which ensures precise warm sensation. However, the underlying mechanisms remain unclear. Here we show that STIM1, an endoplasmic reticulum (ER) resident transmembrane protein that responds to both ER Ca2+ depletion and heat, mediates temperature-induced Ca2+ influx in skin keratinocytes via coupling to Orai Ca2+ channels in plasma membrane. Behaviorally, the keratinocyte-specific knockout of STIM1 shifts the optimal preference temperature (OPT) of mice from ~32 °C to ~34 °C, resulting in a strikingly reversed preference between 32 °C and 34 °C. Importantly, the thermally inactive STIM1-ΔK knock-in mice show altered OPT and warm preference behaviors as well, demonstrating the requirement of STIM1 thermosensitivity for warm sensation. Furthermore, the wild-type and mutant mice prefer temperatures closer to their respective OPTs, but poorly distinguish temperatures that are equally but oppositely deviated from their OPTs. Mechanistically, keratinocyte STIM1 affects the in vivo warm responses of sensory neurons by likely involving TRPA1 as a downstream transduction channel. Collectively, our data suggest that STIM1 serves as a novel in vivo thermosensor in keratinocytes to define the OPT, which might be utilized as a peripheral reference temperature for precise warm sensation.

Investigating impact of converging training walls of the ogee spillways on hydraulic performance

Due to their economical and structural aspects, ogee-crested spillways can be constructed and operated in a wide variety of situations. In this study, a three-dimensional physical model (1:50 scale) was planned and constructed to investigate the impact of converging training walls of the ogee spillways with a curve axis on flow characteristics such as the discharge coefficient, free surface profile, flow depth and pressure on the spillway. For this purpose, the spillway was constructed, tested and verified in both the symmetrical and asymmetrical convergence of training walls ranging from 0° to 120°. Observations from flow depth and piezometric pressure along the spillway in various convergence angles indicate that as θ increases, the flow depth and piezometric pressure increase at the bottom and the toe of the spillway model. Also, in convergence angles of 60° and 90° tested in both symmetric and asymmetric states, the angles with lower Lch/L have larger flow depth and piezometric pressure. The results of the experiments indicated that in the converging ogee spillway, by increasing the total upstream head, the discharge coefficient shows increment for each of the convergence angles (θ’s) and eventually the downstream flow changes its condition to either supercritical or critical stages. It must be considered that the discharge coefficient is independent of symmetric or asymmetric situations. On the other hand, at the submergence stage for the spillway, the difference in the discharge coefficient can be due to tailwater submergence occurring in some convergence angles. Also, the flow depth and the piezometric pressure on the bottom and the toe of the spillway increased more in the symmetrical convergence angles in comparison with the asymmetrical convergence angles. Also, by decreasing the downstream channel width to the crest length (Lch/L), the flow depth and piezometric pressure increase subsequently. Results approved that the 60° convergence is the most economic convergence angle due to its capability in passing the largest flow discharge in the maximum head. The reason for this choice is that the crest length of this angle is 33% lesser than that of 120° convergence.

Free Space Optical Communication in Long-Reach Unidirectional Ring-Architecture Fiber Network

In the work, a ring-constructed wavelength-division-multiplexing (WDM) access system for delivering multiple free space optical (FSO) wireless signals is investigated. To reach the FSO transmission through single-mode fiber (SMF) connection, the optical wireless unit (OWU) and remote OWU are designed in the WDM network. The downstream and upstream WDM FSO channels could be transmitted in unidirectional propagation with the same wavelength. Hence, the presented ring-based WDM network not only can transmit the FSO signal, but also can circumvent the Rayleigh backscattering (RB) interferometric beat noise. In addition, according to the experimental results, the SMF and FSO transmission lengths can reach 50 km and 500 to 1000 m at the forward error correction (FEC) level without using optical amplification and dispersion compensation, respectively, when four WDM wavelengths are exploited experimentally for demonstration.

Mechanisms and Regulation of Neuronal GABAB Receptor-Dependent Signaling.

γ-Aminobutyric acid B receptors (GABABRs) are broadly expressed throughout the central nervous system where they play an important role in regulating neuronal excitability and synaptic transmission. GABABRs are G protein-coupled receptors that mediate slow and sustained inhibitory actions via modulation of several downstream effector enzymes and ion channels. GABABRs are obligate heterodimers that associate with diverse arrays of proteins to form modular complexes that carry out distinct physiological functions. GABABR-dependent signaling is fine-tuned and regulated through a multitude of mechanisms that are relevant to physiological and pathophysiological states. This review summarizes the current knowledge on GABABR signal transduction and discusses key factors that influence the strength and sensitivity of GABABR-dependent signaling in neurons.

Is the topography playing a dual role in controlling downstream channel morphology of a monsoon dominated Dwarkeswar River, Eastern India?

This study focuses on the role of topography in downstream changes in channel morphology of a monsoon dominated Dwarkeswar River with sixty cross-sections. Bankfull channel characteristics, flow characteristics, sediment characteristics and channel pattern were analysed with respect to dissected plateau, plateau-fringe and alluvial plain using statistical analysis. There was a significantly positive relation with distance from source and width (r = 0.874), width/depth ratio (r = 0.607) and flow area (r = 0.926) in the dissected plateau, although a significantly negative relation was found in the alluvial plain (width (r = −0.963), width/depth ratio (r = −0.897), and flow area (r = −0.821)). Overall, the channel dimensions diminished in the alluvial area by 6–7 times. In both these cases, TSI values were higher than the HSI. In the PCA-1, topographic factors were more dominant and the role of drainage area, elevation, slope, basin shape and depth of sediment were opposite to each other in comparison with dissected plateau and alluvial plain.

DUSTBot: A duplex and stealthy P2P-based botnet in the Bitcoin network.

As the root cause of illegal cyber activities, botnets are evolving continuously over the last two decades. Current researches on botnet command and control mechanism based on blockchain network suffer from high economic cost, single point of failure, and limited scalability. In this paper, we present DUSTBot, a novel P2P botnet model based on Bitcoin transactions to prepare for new cyber threats. Specifically, a covert, duplex, and low-cost command and control (C&C) channel in the Bitcoin network is presented in our work. DUSTBot uses the Bitcoin main network as the downstream channel while using the Bitcoin testnet as the upstream channel. Furthermore, the peer list exchange algorithm based on the Ethereum block hash proposed in this paper is effective against routing table poisoning attack and P2P botnet crawling. The robustness of DUSTBot against node removal is studied through constructing the botnet with a P2P simulator. We deploy the implementation of DUSTBot on cloud platforms to test its feasibility and performance. Moreover, the stealthiness of DUSTBot and the effectiveness of the proposed peer list exchange algorithm are evaluated. The results demonstrate the feasibility, performance, stealthiness, and robustness of DUSTBot. In the end, possible countermeasures are discussed to mitigate similar threats in the future.

Service providers and firm performance: investigating the non-linear effect of dependence

PurposeServitized manufacturers can leverage close relationships with external providers of product-related services to mobilize value creation and improve the responsiveness of their offerings to customer needs. The purpose of this paper is to investigate the economic link between the relational embeddedness of external service providers, as arising from the key dimension of dependence, and firm performance.Design/methodology/approachThe study evaluates financial statement data pertaining to 190 dyadic relationships of servitized manufacturers with service providers operating in downstream channels and accounting for more than 10 per cent of their revenue.FindingsThe results indicate that service providers’ dependence has an inverted U-shaped relationship with manufacturers’ return-on-assets (ROA), via non-linear effects on return-on-sales and asset turnover. The results therefore suggest that the observed U-shaped relationship for ROA is driven by diminishing returns of dependence in terms of both differentiation ability and operational efficiency.Research limitations/implicationsFuture research could examine other dimensions of embeddedness, as well as contingency factors that may influence the embeddedness–performance relationship.Practical implicationsThe study conclusions suggest that managers of servitized firms should foster the embeddedness of external service providers, but they should also be careful to maintain an adequate level of dependence to maximize benefits and minimize liabilities.Originality/valueThe study adds to the limited research delving into inter-firm relationships between servitized manufacturers and external service providers. It empirically demonstrates the economic effects of service providers’ dependence-based embeddedness, challenging the general assumption about a monotonic positive effect of relational embeddedness.

Temporal Adjustment of Channel Geometry and Spatial Changes in Riverbed Materials along the Downstream Channels of Large Dams in the Geum River basin

Temporal Adjustment of Channel Geometry and Spatial Changes in Riverbed Materials along the Downstream Channels of Large Dams in the Geum River basin

A silicon-based compact triplexer using Bragg grating assisted non-reciprocal single microring resonator

An ultra-compact silicon triplexer based on waveguide Bragg grating assisted non-reciprocal optical ring add-drop filter has been proposed. This novel scheme consists of two straight strip waveguides laterally coupled to a microring resonator. A magneto-optically active material deposited inside the microcavity is etched to induce strong non-reciprocity, which can cause resonance wavelength splitting ΔλMO of two counter propagating modes. Uniform Bragg grating reflector is fabricated in proximity to one of the input/output (I/O) ports. As a result, two downstream WDM channels (1490 nm/1550 nm) can be separated into the output ports of strip waveguide below the ring resonator, while the third channel considered as upstream signal is transmitted through the waveguide above the microring without any interaction with either the microring resonator or the waveguide Bragg grating reflector. Results show that a total length of 13.5 μm with the highest isolation ratio (IR) of 35 dB is obtained at the adjacent ports of the same strip waveguide; the lowest crosstalk (XT) of −38 dB for 1310 nm channel has also been obtained.

Dynamic 3D Simulation of Flood Risk Based on the Integration of Spatio-Temporal GIS and Hydrodynamic Models

Dynamic visual simulation of flood risk is crucial for scientific and intelligent emergency management of flood disasters, in which data quality, availability, visualization, and interoperability are important. Here, a seamless integration of a spatio-temporal Geographic Information System (GIS) with one-dimensional (1D) and two-dimensional (2D) hydrodynamic models is achieved for data flow, calculation processes, operation flow, and system functions. Oblique photography-based three-dimensional (3D) modeling technology is used to quickly build a 3D model of the study area (including the hydraulic engineering facilities). A multisource spatio-temporal data platform for dynamically simulating flood risk was built based on the digital earth platform. Using the spatio-temporal computation framework, a dynamic visual simulation and decision support system for flood risk management was developed for the Xiashan Reservoir. The integration method proposed here was verified using flood simulation calculations, dynamic visual simulations, and downstream river channel and dam-break flood simulations. The results show that the proposed methods greatly improve the efficiency of flood risk simulation and decision support. The methods and system put forward in this study can be applied to flood risk simulations and practical management.

Numerical study of cascading dam-break characteristics using SWEs and RANS

AbstractThis paper investigates the cascading dam-break flood propagation on the downstream sloping channel and reservoir using the shallow water equations (SWEs) and the Reynolds-average Navier-Stokes equations (RANS). The calculated surface profiles, stage hydrographs and maximum run-up heights for 24 sets of initial conditions are elaborately compared with the experimental measurements, which show the SWEs reproduce the wave oscillation evolution and the maximum run-up height inaccurately. The maximum run-up heights calculated by the SWEs are all smaller than those by the RANS and the measured results, the maximum errors are within −10% to −25%, which may predict delay of the downstream dam-break. However, the maximum errors calculated by the RANS are within ±10%. So the RANS predict more accurate results than the SWEs. Additionally, the generation of short waves must be below a certain upstream-to-downstream ‘depth ratio’, roughly the ‘depth ratio’ &amp;lt;2/3 in this study. If the ratio is too high, it is difficult to form a wavy push due to air entrainment and turbulence. The SWEs predict more accurate results for shallow initial depths than deep initial depths. Therefore, the advantage of the RANS can be more obvious for deep initial depths.