Service Curve Research Articles

Cloud‐assisted elliptic curve password authenticated key exchange protocol for wearable healthcare monitoring system

SummaryWearable devices (WDs) adopting advanced microsensors and IoT technology are facing severe security risks in the process of building wearable healthcare monitoring system. In particular, new requirements are proposed for the security of the identity authentication and key agreement protocol as well as the consumption of computing resources for WDs, such as replay attack, modification attack, server‐spoofing attack, privileged‐insider attack, and denial‐of‐service attack. To satisfy such requirements, cloud‐assisted EC password authenticated key exchange (CEPAK), an identity dynamic authentication and key agreement protocol, is proposed, and it uses a cloud‐assisted authentication service and elliptic curve algorithm. The capability of CEPAK protocol is analyzed to deal with network attack and consumption of computing resources and communication resources. It is shown that on the basis of satisfying the security requirements of the system, the cloud‐assisted authentication server can greatly share the consumption of computing resources of intelligent terminals, effectively save the computing resources of intelligent terminals, and improve the system's ability to deal with attacks caused by consumption of computing resources.

An Improved SCS-CN Method Incorporating Slope, Soil Moisture, and Storm Duration Factors for Runoff Prediction

Soil Conservation Service Curve Number (SCS-CN) is a popular surface runoff prediction method because it is simple in principle, convenient in application, and easy to accept. However, the method still has several limitations, such as lack of a land slope factor, discounting the storm duration, and the absence of guidance on antecedent moisture conditions. In this study, an equation was developed to improve the SCS-CN method by combining the CN value with the tabulated CN2 value and three introduced factors (slope gradient, soil moisture, and storm duration). The proposed method was tested for calibration and validation with a dataset from three runoff plots in a watershed of the Loess Plateau. The results showed the model efficiencies of the proposed method were improved to 80.58% and 80.44% during the calibration and validation period, respectively, which was better than the standard SCS-CN and the other two modified SCS-CN methods where only a single factor of soil moisture or slope gradient was considered, respectively. Using the parameters calibrated and validated by dataset of the initial three runoff plots, the proposed method was then applied to runoff estimation of the remaining three runoff plots in another watershed. The proposed method reduced the root-mean-square error between the observed and estimated runoff values from 5.53 to 2.01 mm. Furthermore, the parameters of soil moisture (b1 and b2) is the most sensitive, followed by parameters in storm duration (c) and slope equations (a1 and a2), and the least sensitive parameter is the initial abstraction ratio λ on the basis of the proposed method sensitivity analysis. Conclusions can be drawn from the above results that the proposed method incorporating the three factors in the SCS method may estimate runoff more accurately in the Loess Plateau of China.

Estimation of Initial Abstraction for Hydrological Modeling Based on Global Land Data Assimilation System–Simulated Datasets

AbstractInitial abstraction (Ia) is a sensitive parameter in hydrological models, and its value directly determines the amount of runoff. Ia, which is influenced by many factors related to antecedent watershed condition (AWC), is difficult to estimate due to lack of observed data. In the Soil Conservation Service curve number (SCS-CN) method, it is often assumed that Ia is 0.2 times the potential maximum retention S. Yet this assumption has frequently been questioned. In this paper, Ia/S and factors potentially influencing Ia were collected from rainfall–runoff events. Soil moisture and evaporation data were extracted from GLDAS-Noah datasets to represent AWC. Based on the driving factors of Ia, identified using the Pearson correlation coefficient and maximal information coefficient, artificial neural network (ANN)-estimated Ia was applied to simulate the selected flood events in the Hydrologic Engineering Center Hydrologic Modeling System (HEC-HMS) model. The results indicated that Ia/S varies over different events and different watersheds. Over 75% of the Ia/S values are less than 0.2 in the two study areas. The driving factors affecting Ia vary over different watersheds, and the antecedent precipitation index appears to be the most influential factor. Flood simulation by the HEC-HMS model using statistical Ia gives the best fitness, whereas applying ANN-estimated Ia outperforms the simulation with median Ia/S. For over 60% of the flood events, ANN-estimated Ia provided better fitness in flood peak and depth, with an average Nash–Sutcliffe efficiency coefficient of 0.76 compared to 0.71 for median Ia/S. The proposed ANN-estimated Ia is physically based and can be applied without calibration, saving time in constructing hydrological models.

Surface runoff in urban areas: The role of residential cover and urban growth form

In the context of rapid urbanization and climate change, understanding the impact of urban dynamics on surface runoff is important. For future urban planning, there is a particular knowledge gap regarding the factors that affect surface runoff to improve urban resilience to local flooding. This study explored the impacts of different urban dynamics on surface water runoff considering the surface cover characteristics of different residential types (i.e., low- and high-density settlements) in the city of Munich, Germany. The surface cover characteristics were quantified using the ‘i-Tree Canopy’ method based on high-resolution aerial images. The surface runoff was simulated by the Soil Conservation Service Curve Number (SCS-CN) method. Meanwhile, the impacts of different urban dynamics on surface runoff were compared by incorporating a scenario-based urban dynamic modeling approach. The results suggest that, compared with low-density settlements, high-density settlement areas tend to generate more surface runoff within the neighborhood because they have considerably less vegetative surfaces and more built ones. As the development of low-density settlements leads to a greater loss of green and open spaces in the surrounding peri-urban areas, however, the compact growth scenarios characterized by high-density settlements have advantages over low-density scenarios in terms of overall surface runoff reduction at the city scale. Thus, the trade-off between the neighborhood and city scale should be considered when promoting nature-based solutions for surface runoff mitigation. Moreover, the approach presented here can be used as an effective planning tool supporting various urban contexts.

Correlation between runoff volume and land use changes using SCS-CN method for Sungai Gombak catchment

This research focuses on river modeling using the input precipitation and land use system Soil Conservation Service Curve Number (SCS-CN) using InfoWorks RS (IWRS) and Geographical Information System (GIS). The purpose of this study is to measure the volume of runoff based on the year selected for the Sungai Gombak model with changes in land use base. Sungai Gombak is part of the upper basin of the Sungai Klang. The Sungai Klang basin area has undergone significant urbanization, especially upstream in Sungai Batu, Sungai Gombak and Sungai Klang. This urbanization is the most significant changes in land use happening within the basin of the lake. For the Sungai Gombak catchment, the transformation of the undeveloped area that lead to Sungai Gombak changing the amount of runoff. Six rainfall stations were selected to model the river and then the average catchment rainfall for each catchment was interpolated using Thiessen method from the available rainfall station. Three rainfall events were chosen based on the flood history reported by the Department of Irrigation and Drainage (DID) in the Sungai Gombak. The results indicate that the CN value rises from year to year due to changes in landscape patterns that indirectly influence ecological processes and decrease the stream flow time concentration.

Improved SMA-based SCS-CN method incorporating storm duration for runoff prediction on the Loess Plateau, China

Abstract In the Soil Conservation Service Curve Number (SCS-CN) method for estimating runoff, three antecedent moisture condition (AMC) levels produce a discrete relation between the curve number (CN) and soil water content, which results in corresponding sudden jumps in estimated runoff. An improved soil moisture accounting (SMA)-based SCS-CN method that incorporates a continuous function for the AMC was developed to obviate sudden jumps in estimated runoff. However, this method ignores the effect of storm duration on surface runoff, yet this is an important component of rainfall-runoff processes. In this study, the SMA-based method for runoff estimation was modified by incorporating storm duration and a revised SMA procedure. Then, the performance of the proposed method was compared to both the original SCS-CN and SMA-based methods by applying them in three experimental watersheds located on the Loess Plateau, China. The results indicate that the SCS-CN method underestimates large runoff events and overestimates small runoff events, yielding an efficiency of 0.626 in calibration and 0.051 in validation; the SMA-based method has improved runoff estimation in both calibration (efficiency = 0.702) and validation (efficiency = 0.481). However, the proposed method performed significantly better than both, yielding model efficiencies of 0.810 and 0.779 in calibration and validation, respectively.

Assessment of Soil and Water Conservation Practices in the Loess Hilly Region Using a Coupled Rainfall-Runoff-Erosion Model

Soil and water conservation practices (SWCPs) are widely used to control soil and water loss. Quantifying the effect of SWCPs and climate change on soil and water erosion is important for regional environmental management. In this study, the Soil Conservation Service Curve Number (SCS-CN) and the Modified Universal Soil Loss Equation (MUSLE) were employed to investigate the patterns of surface runoff and soil erosion with different SWCPs in the hilly region on the Loess Plateau of China. The impact of climate change under RCP4.5 and RCP8.5 emission scenarios was considered from 2020 to 2050. Surface runoff grew with the increased rainfall and rainfall erosivity, while soil erosion presented large variations between years due to uneven distribution of rainfall and rainfall erosivity under two scenarios. Different SWCPs significantly reduced surface soil and water loss. Compared with bare slopes, the reduction rates were 15–40% for surface runoff and 35–67% for soil erosion under RCP4.5 and RCP8.5 emission scenarios, respectively. The combination of shrub and horizontal terracing was recommended due to its low water cost for sediment control among seven SWCPs.

Verification of a New Spatial Distribution Function of Soil Water Storage Capacity Using Conceptual and SWAT Models

The Soil Conservation Service Curve Number (SCS-CN) method is widely used in conceptual rainfall-runoff models for describing the runoff response with a curve, which is a function of the cumulative storm rainfall and antecedent wetness conditions. To improve the SCS-CN method, a new distribution function was recently proposed to unify the surface runoff modeling of the SCS-CN method and probability-distributed functions in the variable infiltration capacity (VIC) and Xin’anjiang models. This study aims to verify the new distribution function in a conceptual rainfall-runoff model and in the Soil and Water Assessment Tool (SWAT) by using real catchments. The Xunhe River basin in China and other basins in the United States were used as case studies. Results show that more observed variability in streamflow is captured when using the new spatial distribution function of soil water storage capacity in the conceptual runoff model. Specifically, there is a 9.8% average increase in the Nash-Sutcliffe efficiency (NSE), while simultaneously reducing the bias and mean relative absolute error (MRAE). When using the new distribution in SWAT, the model is able to better estimate the observed streamflow as indicated by higher NSE values for most of the basins. Akaike information criterion (AIC) is used for validating the goodness-of-fit when the number of parameters and model structure change. Further findings suggest that the estimated variance is more sensitive to the value of the new shape parameter a when soil water content is low in the early stage of rainfall. Therefore, the proposed new distribution function is shown to be effective in improving the accuracy of simulating streamflow for both conceptual and SWAT models.

Assessing the Effect of Land Use Change on Surface Runoff in a Rapidly Urbanized City: A Case Study of the Central Area of Beijing

The change in land use during the process of urbanization affects surface runoff and increases flood risk in big cities. This study investigated the impact of land use change on surface runoff in Beijing’s central area during the period of rapid urbanization from 1984 to 2019. Land use maps of 1984, 1999, 2009, and 2019 were generated by image classification of Landsat images. Surface runoffs were calculated with the Soil Conservation Service curve number (SCS-CN) model. Correlation analysis was used to identify the dominant factor of land use change affecting surface runoff. The result showed that the variation trend of surface runoff was consistent with the trend of impervious land in Beijing’s central area, which increased during 1984~2009 and decreased during 2009~2019. Correlation analysis showed that changes in surface runoff were most strongly correlated with changes in impervious surfaces when compared with the correlation of runoff with other types of land use. The results of this study may provide a reference for city flood control and urban planning in fast growing cities worldwide, especially in developing countries.

Assessment of modified curve number method by evaluation of runoff depth in Sulak basin-Iraq

Traditional hydrological analysis used maps and ground survey as tools to obtain the basic parameters of the watershed. However, for large catchment area the above criteria are both costly and time consuming. In this research, a hydrological model modified natural resources conservation service curve number (NRCS-CN) and geographical information system GIS technique are used together to obtain the runoff depth for Sulak catchment area that located in the northern western part of Iraq. The basin divided into three sub-basins, runoff has been estimate for each sub-basin by three approaches. The research detect that the slope parameter affects runoff estimation significantly also its found that for each sub-watershed runoff varies drastically from sub-watershed to sub-watershed of Sulak basin. The analysis of variance test showed that there was significant difference between each curve number value for each sub-watershed, accordingly runoff calculated by Williams method gives valves above the average comparing with other methods. Total runoff estimated by three approaches for entire catchment area which shows that around 51% of total runoff is generated in months January and February, That because of heavy rainfall and high soil moisture content (antecedent moisture content AMC-III) during that period.

A streamflow hydrograph analysis and simulation for a study case watershed

The streamflow hydrograph analysis and simulation for a study case watershed was carried out using the hydrologic engineering centre - geospatial hydrologic modelling system (HEC-GeoHMS) and the hydrologic engineering centre - hydrologic modelling system (HEC-HMS) software coupling. HEC-GeoHMS is integrated in a geographic information system (GIS) so as to develop a terrain's pre-processing tool and to generate output files which are inputted to the hydrologic model. Soil map data, land use map and digital elevation model (DEM) were used in order to delineate the physical watershed's characteristics. The runoff estimation was based on the soil conservation service curve number (SCS-CN) approach while the watershed's outflow estimation was carried out by employing SCS unit hydrograph method. The rainfall - runoff modelling is applied on a storm event which occurred on 01/10/2005 at Kastaneri watershed. The coupled hydrological models simulated runoff hydrograph for the latter storm event whilst the CN and the peak discharge values were computed equal to 69.5 and 72.8 m3/s respectively.

Influence of Land Use Land Cover Change on Groundwater Recharge in the Continental Terminal Area of Abidjan, Ivory Coast

The process by which rainfall reaches the aquifer in a sedimentary area is infiltration. This process could be affected quantitatively or qualitatively by the changes in the land use land cover (LULC) as a result of anthropogenic activities which could affect groundwater reserves. This study focuses on the influence of LULC change on groundwater recharge in the context of urbanization and population growth. Four weather stations data and satellite image data were used in order to evaluate water infiltration which is the amount of water that reaches the piezometric surface from 1990 to 2016. The spatial-temporal LULC change in relation to urbanization sprawl was assessed based on a series of Landsat images for 1990, 2000 and 2016. The maximum likelihood pixel-based on classification method was used to analyze the spatial-temporal LULC dynamics. The Thiessen polygon method was used for the mean area precipitation computation. The recharge was determined using water balance method after determining the runoff based on the Soil Conservation Service curve number method. The results show an increase in built-up and agricultural land, while the forest and shrub areas declined with water body remaining unchanged over the period 1990-2016. The decline in forest could be imputed to the demographic and socio-economic growth as expressed by the expansion of agriculture and urbanization. Groundwater recharge and runoff results are respectively 34%, 20% in 1999; 21%, 46% in 2000 and 26%, 14% in 2016 of rainfall and show their strong dependence on precipitation and LULC change.

Identification of groundwater recharge-based potential rainwater harvesting sites for sustainable development of a semiarid region of southern India using geospatial, AHP, and SCS-CN approach

Groundwater recharge-based rainwater harvesting (RWH) is a standout among the most capable structures to reduce water deficit issues and to build the accessibility of water for sustainable development in the semiarid regions because of absence of precipitation and flighty precipitation patterns. The delineation of potential recharge zone (PRZ) with RWH and selection of sites cause a greater dispute for the water stakeholders because of deficient framework. The essential thematic layer such as land use/land cover, soil, geology, vadose zone, drainage density, slope, and runoff were used for delineation of PRZ and RWH sites. Analytical hierarchical process (AHP) was carried out by assigning different weights to different thematic layers to determining the PRZ and RWH sites. The present study endeavours to decide the suitable areas for RWH using Soil Conservation Service curve number (SCS-CN) based on surface runoff with geospatial techniques. The enlargement of water asset is proposed by the development of RWH structures such as farm pond (FP), percolation tank (PT), check dam (CD), and gully plug (GP) having 73.53% (358.08 km2) appropriate for FP, 8.62% (42 km2) reasonable for PT, 17.48% (85.16 km2) reasonable for CD, and 0.35% (1.71 km2) for GP of the present study region. Based on integrated mission of sustainable development specification, 20 PT, 11 FP, and 4 CD were identified having 85%, 90%, and 100% accuracy in agreement between existing structures and predicted potential site. The present study approach demonstrates the higher accuracy for identification of RWH at any scale with sustainable water resources development.

Estimation of surface runoff using NRCS curve number in some areas in northwest coast, Egypt

The sustainable agricultural development in the northwest coast of Egypt suffers constantly from the effects of surface runoff. Moreover, there is an urgent need by decision makers to know the effects of runoff. So the aim of this work is to integrate remote sensing and field data and the natural resource conservation service curve number model (NRCS-CN).using geographic information systems (GIS) for spatial evaluation of surface runoff .CN approach to assessment the effect of patio-temporal variations of different soil types as well as potential climate change impact on surface runoff. DEM was used to describe the effects of slope variables on water retention and surface runoff volumes. In addition the results reflects that the magnitude of surface runoff is associated with CN values using NRCS-CN model . The average of water retention ranging between 2.5 to 3.9m the results illustrated that the highest value of runoff is distinguished around the urban area and its surrounding where it ranged between 138 - 199 mm. The results show an increase in the amount of surface runoff to 199 mm when rainfall increases 200 mm / year. The north of the area may be exposed to erosion hazards more than the south and a change in the soil quality may occur in addition to the environmental imbalance in the region.

A Calibrated, Watershed-Specific SCS-CN Method: Application to Wangjiaqiao Watershed in the Three Gorges Area, China

The Soil Conservation Service curve number ( S C S-C N) method is one of the most popular methods used to compute runoff amount due to its few input parameters. However, recent studies challenged the inconsistent runoff results obtained by the method which set the initial abstraction ratio λ as 0.20. This paper developed a watershed-specific S C S-C N calibration method using non-parametric inferential statistics with rainfall–runoff data pairs. The proposed method first analyzed the data and generated confidence intervals to determine the optimum values for S C S- C N model calibration. Subsequently, the runoff depth and curve number were calculated. The proposed method outperformed the runoff prediction accuracy of the asymptotic curve number fitting method, linear regression model and the conventional S C S-C N model with the highest Nash–Sutcliffe index value of 0.825, the lowest residual sum of squares value of 133.04 and the lowest prediction error. It reduced the residual sum of squares by 66% and the model prediction errors by 96% when compared to the conventional S C S-C N model. The estimated curve number was 72.28, with the confidence interval ranging from 62.06 to 78.00 at a 0.01 confidence interval level for the Wangjiaqiao watershed in China.

Improved Delay Bound for a Service Curve Element With Known Transmission Rate

Network calculus is often used to prove delay bounds in deterministic networks, using arrival and service curves. We consider a FIFO system that offers a rate-latency service curve and where packet transmission occurs at line rate without pre-emption. The existing network calculus delay bounds take advantage of the service curve guarantee but not of the fact that transmission occurs at full line rate. In this letter, we provide a novel, improved delay bound which takes advantage of these two features. Contrary to existing bounds, ours is per-packet and depends on the packet length. We prove that it is tight.

Quantitative assessment of surface runoff at arid region: a case study in the Middle of Nile Delta

BackgroundEvaluation of surface runoff is an essential factor in the precision water and soil conservation management through their main extreme impacts on soil properties. The natural resource conservation service curve number model (NRCS-CN) model is used to estimate the magnitude of runoff. Collected topographic data is used to explain the effects of slope variation on water retention and surface runoff. Twenty-eight soil profiles are prepared in Nile delta, Egypt to cover different geomorphic units and hydrological soil groups in the study area.ResultsThe results revealed that the highest value of surface runoff was distinguished close to the urban area and ranges between 40 and 50 mm. In urban areas, the surfaces are paved and there are no infiltration of water. Consequently, the runoff water directly flows to the storm channels. Runoff values ranging between 30 and 40 mm occurred at the north of the study area. The sloping surface and the nature of the clay soil contributed to generate more runoff than do lowland areas.ConclusionThe study presented and tested the hydric runoff estimation based-model on the integrating of hydric balance parameters. The GIS tools analyze and compose these parameters to perform an indirect method for the quantity of water that results in direct surface runoff flow. This method helps to gain clear imaging of the surface runoff risks in the study area.

Sensitivity of Direct Runoff to Curve Number Using the SCS-CN Method

This study explores the impact of runoff curve number (CN) on the hydrological model outputs for the Morai watershed, Sindh-Pakistan, using the Soil Conservation Service Curve Number (SCS-CN) method. The SCS-CN method is an empirical technique used to estimate rainfall-runoff volume from precipitation in small watersheds, and CN is an empirically derived parameter used to calculate direct runoff from a rainfall event. CN depends on soil type, its condition, and the land use and land cover (LULC) of an area. Precise knowledge of these factors was not available for the study area, and therefore, a range of values was selected to analyze the sensitivity of the model to the changing CN values. Sensitivity analysis involves a methodological manipulation of model parameters to understand their impacts on model outputs. A range of CN values from 40-90 was selected to determine their effects on model results at the sub-catchment level during the historic flood year of 2010. The model simulated 362 cumecs of peak discharge for CN=90; however, for CN=40, the discharge reduced substantially to 78 cumecs (a 78.46% reduction). Event-based comparison of water volumes for different groups of CN values—90-75, 80-75, 75-70, and 90-40 —showed reductions in water availability of 8.88%, 3.39%, 3.82%, and 41.81%, respectively. Although it is known that the higher the CN, the greater the discharge from direct runoff and the less initial losses, the sensitivity analysis quantifies that impact and determines the amount of associated discharges with changing CN values. The results of the case study suggest that CN is one of the most influential parameters in the simulation of direct runoff. Knowledge of accurate runoff is important in both wet (flood management) and dry periods (water availability). A wide range in the resulting water discharges highlights the importance of precise CN selection. Sensitivity analysis is an essential facet of establishing hydrological models in limited data watersheds. The range of CNs demonstrates an enormous quantitative consequence on direct runoff, the exactness of which is necessary for effective water resource planning and management. The method itself is not novel, but the way it is proposed here can justify investments in determining the accurate CN before initiating mega projects involving rainfall-runoff simulations. Even a small error in CN value may lead to serious consequences. In the current study, the sensitivity analysis challenges the strength of the results of a model in the presence of ambiguity regarding CN value.

Effects of hillslope geometry on spatial infiltration using the TOPMODEL and SCS-CN models

ABSTRACTThe estimation of infiltration is a main issue in runoff simulation. The geometry of hillslopes (plan shape and profile curvature) may affect the responses, as well as infiltration over the hillslopes. In this study, the equations of TOPMODEL (a topography-based model) were applied to complex hillslopes to develop the complex TOPMODEL. This model was coupled with the SCS-CN (Soil Conservation Service Curve Number) model to examine the effects of geometry on infiltration and derive a saturation excess-based curve number (CN). The effects of plan shape and profile curvature upon the spatial distribution of CN and infiltration were studied. The results show that convergent hillslopes have 15.4% less infiltration and divergent hillslopes have 7.8% more infiltration than parallel ones. The infiltration over concave hillslopes is 13.5% lower and infiltration over convex hillslopes 5.8% higher than for straight ones. The degree of convergence/divergence has a greater effect on the CN compared to that of profile curvature.

Geospatial Modelling of Watershed Peak Flood Discharge in Selangor, Malaysia

Conservative peak flood discharge estimation methods such as the rational method do not take into account the soil infiltration of the precipitation, thus leading to inaccurate estimations of peak discharges during storm events. The accuracy of estimated peak flood discharge is crucial in designing a drainage system that has the capacity to channel runoffs during a storm event, especially cloudbursts and in the analysis of flood prevention and mitigation. The aim of this study was to model the peak flood discharges of each sub-watershed in Selangor using a geographic information system (GIS). The geospatial modelling integrated the watershed terrain model, the developed Soil Conservation Service Curve Cumber (SCS-CN) and precipitation to develop an equation for estimation of peak flood discharge. Hydrological Engineering Center-Hydrological Modeling System (HEC-HMS) was used again to simulate the rainfall-runoff based on the Clark-unit hydrograph to validate the modelled estimation of peak flood discharge. The estimated peak flood discharge showed a coefficient of determination, r2 of 0.9445, when compared with the runoff simulation of the Clark-unit hydrograph. Both the results of the geospatial modelling and the developed equation suggest that the peak flood discharge of a sub-watershed during a storm event has a positive relationship with the watershed area, precipitation and Curve Number (CN), which takes into account the soil bulk density and land-use of the studied area, Selangor in Malaysia. The findings of the study present a comparable and holistic approach to the estimation of peak flood discharge in a watershed which can be in the absence of a hydrodynamic simulation model.