Runoff Coefficient Research Articles

Enhancing rainfall-runoff model accuracy with machine learning models by using soil water index to reflect runoff characteristics.

The advancement of data-driven models contributes to the improvement of estimating rainfall-runoff models due to their advantages in terms of data requirements and high performance. However, data-driven models that rely solely on rainfall data have limitations in responding to the impact of soil moisture changes and runoff characteristics. To address these limitations, a method was developed for selecting predictor variables that utilize the accumulation of rainfall at various time intervals to represent soil moisture, the changes in the runoff coefficient, and runoff characteristics. Furthermore, this study investigated the utility of rainfall products [such as climate hazards group infrared precipitation with station data (CHIRPS) and global precipitation measurement (GPM)] for representing rainfall data, while also using the soil water index (SWI) to enhance runoff estimation. To assess these methods, the random forest (RF) and artificial neural network (ANN) models were utilized to simulate daily runoff. Incorporating both the rainfall and SWI data led to improved outcomes. The RF demonstrated superior performance compared with the ANN and the conceptual model, without the need for baseflow separation or antecedent runoff. Furthermore, accumulated rainfall was shown to be a valuable input for the models. These findings should facilitate the estimation of runoff in locations with limited measurement data on rainfall and soil moisture by utilizing remote sensing data.

Urban Flood Mitigation by Implementing LIDs (Case Study: Bendung Watershed in Palembang City)

Urban areas continue to be affected by flooding, necessitating more sustainable and effective adaptation strategies and mitigation initiatives. This study investigates the potential flood reduction capability achieved through implementing various green infrastructures known as low-impact development (LID). The Bendung watershed, in the center of Palembang City, with a total area of 18.37 km2, is used as the study area to evaluate the performance of LID infrastructure in reducing flood parameters, including total runoff volume, peak runoff discharge, runoff coefficient, and flooding area. Five types of LID infrastructure were simulated, namely bio-retention cells, rain gardens, permeable pavements, rain barrels, and recharge wells. The flood simulations were performed using four design storms with 2-, 5-, 10-, and 25-year return periods. Hydrologic and hydraulic modeling and simulations were carried out using PCSWMM Professional 2D, and the results were integrated with ArcMap to map the flood inundation. The results of this study demonstrate that with only 9.81 percent of the area occupied by LIDs, a flood reduction of more than 30% can be achieved. In addition, implementing LIDs can help restore the watershed’s hydrological condition to its natural state, as indicated by the decrease in the runoff coefficient. Thus, implementing LIDs in a sustainable urban drainage system must be widely promoted in many urban areas, especially in developed countries like Indonesia. This study can be used as a reference for the local government and authorities to create policies and regulations to establish sustainable flood mitigation measures in Palembang City.

The effect of paving block from plastic waste material in the urban drainage: Study case in residential areas

Large expanses of green, open land are frequently converted as a result of population growth and quick development. This phenomenon causes the decreasing of water infiltration area which has an impact on increasing runoff coefficient. In the urban drainage problem, paving blocks are often used as road pavement construction materials to reduce surface runoff. The aim of this research is to study the characteristic of flow in the paving block made from plastic waste material. The research conducted in the laboratory testing utilizing a rainfall simulator by several variations in slope of 0% to 15%. The findings indicate that paving blocks made from plastic waste have less runoff coefficient than asphalt and/or concrete pavement. There is a correlation between the slope of the land and the runoff coefficient value which the runoff coefficient value increasing as the slope of the land increases. That finding is then applied in urban drainage problem located in the Cipamokolan Village region in Bandung City with the help of SWMM program for drainage calculation. As a result, the runoff discharge is decreasing by implementing the paving block made from plastic waste.

Increasing surface impermeability influences peak discharge with the Snyder method in the Ngadipiro sub-watershed of the Bengawan Solo watershed

This research was conducted to determine the effect of increasing soil impermeability in the Ngadipiro Sub-watershed on Cp and Ct numbers in 2015 and 2021. The measured unit hydrograph is used as a reference in calculating the Synder synthetic unit hydrograph method. Test the validation of the two methods using the correlation coefficient. The results of this study showed an increase in tightness in the form of an increased runoff coefficient from 0.26 in 2015 to 0.34 in 2021. This increase in tightness is also in line with the increase in peak discharge using the Measured unit hydrograph in 2015 of 73.3757 m3/s and 2021 of 139.1005 m3/s. The results obtained using the Snyder method obtained peak discharges in 2015 and 2021 of 75.10 m3/s and 148.89 m3/s. The results of the correlation test between the two methods obtained very strong correlation results with a 2015 R-value of 0.96 and a 2021 R-value of 0.92. The non-physical parameters of the watershed, namely Ct and Cp, were optimal in the Ngadipiro Sub-watershed in 2015, the Ct value was 2.2 and the Cp value was 0.9, while in 2021 the Ct value obtained was 1.3 and the Cp value was 1.1.

An optimization model for the impervious surface spatial layout considering differences in hydrological unit conditions for urban waterlogging prevention in urban renewal

The expansion of impervious surfaces during urbanization, as well as the irrationality of their spatial layout, is one of the main causes of urban waterlogging. Optimizing the spatial layout of impervious surfaces through urban renewal is important for urban waterlogging prevention. The differences in hydrological conditions among different hydrological units affect the optimization efficiency of the spatial layout of impervious surfaces in different hydrological units. Therefore, this study proposes an effective optimization model for impervious surface spatial layout, employing a hybrid approach that couples the Soil Conservation Service Curve Number (SCS-CN) model, nondominated sorting genetic algorithm 2 (NSGA2), and multiple linear programming (MLP) algorithm. This approach is applied in a case study of Guangzhou, China. The results show that (1) compared to the MLP-SCS model, the enhanced model not only provides reduced runoff coefficients but also achieves a better spatial balance of the retention water volume. (2) Compared to the conditions before optimization, medium- and high-density impervious surfaces significantly change after optimization, and the connectivity between patches is reduced. The optimized layout alters the original gradient connection method, preventing the aggregation of runoff from high-density impervious surfaces and thereby reducing the risk of urban waterlogging during heavy rain. This study can provide a reference for optimizing the spatial layout of impervious surfaces aimed at urban waterlogging prevention in urban renewal planning.

Daya Dukung Biofisik Sub Daerah Aliran Sungai Ciujung Hulu, Provinsi Banten

Landuse changes without soil and water conservation-based, especially in the upstream watershed, can drive erosion and degraded land. It affects watershed management. Flood, sedimentation, and discharge fluctuation downstream of Ciujung Watershed are the effect of the degraded land upstream. It affects biophysical carrying capacity. The carrying capacity of the watershed becomes the basis for consideration in the watershed management plan. The purpose of this research is to study the biophysical carrying capacity of the upstream Ciujung Sub-basin. Biophysical aspects of watershed include percentage of degraded land, percentage of vegetation, erosion index, runoff regime coefficient, annual runoff coefficient, sedimentation, flood events, and water use index. It was scored based on Indonesia Forestry Minister Regulation No. P.61/Menhut-II/2014. The result showed that degraded land percentage, erosion index, yearly runoff coefficient, sedimentation, and flood event were severe, vegetation belongs to the very bad category, and water use index were in a medium stage. The carrying capacity in Ciujung Hulu Watershed was in poor condition with a score total of 140,5.

Analyzing Debris Flow: Topographical Data and Discharge Rate Study

This study used an unmanned aerial vehicle (UAV) for aerial photogrammetry at the Seonseri debris flow site in Gokseong-gun, triggered by heavy rainfall in August 2020. Survey data facilitated the generation of orthographic images and high-resolution digital surface mode (DSM). Finite difference method (FDM) numerical analysis simulated debris flow, exploring the impact of discharge rate and topographic data among input variables. Applying the rational formula for determining debris flow discharge rate emphasized the significance of maximum rainfall intensity just before the event, with high estimated values for runoff coefficient and soil concentration. The study highlighted significant variations in debris flow simulation results based on topographical data accuracy, emphasizing the crucial role of precise site-specific topographical data.

Perencanaan Drainase Saluran Terbuka Pada Area Tambang Komoditas Tanah Liat Kabupaten Trenggalek

One of the important aspects in mining activities is the drainage system. A good drainage system can prevent flooding, erosion, landslides, and water pollution caused by mining. The drainage system applied in the clay mining site consists of making drainage channels at the bottom of the mining benches. This is intended to capture the mine runoff water. The mine floor is sloped towards the drainage channel. Data collection is carried out, which includes data on location, area, and slope of the mining area, rainfall, runoff coefficient, and then calculations are performed using the Manning equation to obtain the channel dimensions. The planned open channel dimensions have a channel base width = 0.908 m, flow depth = 0.79 m, wet cross-sectional area = 1.07 m, wet perimeter = 1.943 m, hydraulic radius = 0.39 m, water surface width = 1.824 m, and freeboard = 0.197 m. The construction of the drainage channel is intended so that the water on the mine floor can flow directly to the drainage channel, thus not disturbing the mining activities

THE INFLUENCE OF RECREATION ON THE PROCESSES OF SOIL EROSION IN THE FORESTS OF THE WEST KAZAKHSTAN REGION

The relevance of the topic is determined by the increasing demand for forest recreational resources of the West Kazakhstan region. The forests of the West Kazakhstan region are under the influence of recreational activity, which is growing every year and leads to the transformation of the natural environment. The purpose of the study is to determine the influence of recreation on the processes of soil erosion in the forests of the West Kazakhstan region. An increase in the recreational load and the steepness of the slopes leads to degradation of the forest floor and grassy cover. The remnants of these materials move downhill under the influence of visitors, and the soil surface is compacted. The porosity coefficient of the upper soil layer decreases as recreational loads increase. This leads to a decrease in soil water permeability and an increase in surface water runoff. The study showed that the runoff coefficient, the air-dry mass of the forest floor and the porosity coefficient are closely related. These relationships characterize an increase in the water runoff coefficient with a decrease in the air-dry mass of the forest litter and the porosity coefficient. In the field in 2023, based on the morphological description of the profiles, the degree of soil erosion in the selected woodlands was determined.

Brief communication: A first hydrological investigation of extreme August 2023 floods in Slovenia, Europe

Abstract. Extreme floods occurred from 4 to 6 August 2023 in Slovenia causing three casualties and causing total direct and indirect damage, including post-disaster needs according to the Post-Disaster Needs Assessment (PDNA), close to EUR 10 billion. The atypical summer weather conditions combined with the high air and sea temperatures in the Mediterranean and the high soil moisture led to the most extreme flood event in Slovenia in recent decades. The return periods of both daily and sub-daily precipitation extremes and peak discharges reached 250–500 years, and the runoff coefficient of a typical torrential and mostly forested mesoscale catchment was around 0.5. In addition, flooding, soil erosion, mass movements and river sediment transport processes caused major damage to buildings (more than 12 000 houses) and diverse infrastructure.

Runoff and erosion from three unpaved road segments in northern Vietnam

Study regionTruong Son Commune, Luong Son District, Hoa Binh Province in north Vietnam. Study focusRunoff and erosion from three road surface and three adjacent cutslope plots in a young plantation forest to evaluate how unpaved forest roads affect runoff and erosion. New hydrologic insights for the regionThe 10-m long road surface plots generated similar amounts of runoff with runoff coefficients of 24–32 % over 24 rainstorms divided into an initial wetter period followed by a relatively drier period. Runoff coefficients for the two monitoring periods were not statistically different, and the relatively low runoff coefficients compared to previous studies were due to infiltration outside the narrow compacted tracks created primarily by motorbike traffic. Runoff from the base of the cutslopes varied by a factor of three, associated with the topographic convergence of the hillslopes. Road surface erosion over the two monitoring periods was consistent among the three plots and storm-based sediment production was strongly correlated with both storm precipitation and surface runoff. The amounts of runoff and sediment collected at the base of the cutslopes increased with increasing hillslope convergence, and the mass of collected sediment was 52–97 % of the corresponding amounts from the road surface plots. The results provide data on the extent of unpaved road runoff and erosion in this seasonally wet tropical environment, and the need to consider topographic convergence in road design and drainage.

Impact of LULC changes on hydrological flow regimes and runoff coefficient in Upper Jhelum Basin, India

Impact of LULC changes on hydrological flow regimes and runoff coefficient in Upper Jhelum Basin, India

The Feasibility of Rainwater Harvesting Systems in Buildings with Green Roofs: A Case Study Based on the Köppen Climate Classification

The construction of green roofs (GR) combined with rainwater harvesting systems (RWHSs) in buildings can increase the advantages of each of these technologies, being a very promising solution to combat climate change and increase the sustainability of cities. However, the viability of this joint solution significantly depends on local climatic conditions. The planet’s climate classification, known as the Köppen climate classification, is one of the most widely used climate classification systems. The Köppen climate classification divides climates into five main climate groups, with each group being referenced based on seasonal precipitation and temperature patterns. In the specific case of mainland Portugal, according to the Köppen classification, the climate is divided into two regions. In this article, case studies are developed for two Portuguese climatic regions, seeking to demonstrate the possibility of using the Köppen classification as a decision criterion for the eventual inclusion of rainwater harvesting systems in buildings with green roofs. For this study, the results of a previous study were applied, through which we obtained an expression to determine the runoff coefficients of green roofs common in Portugal, concluding that the Köppen climate classification can be used as a prior decision criterion regarding its incorporation or exclusion in rainwater harvesting system buildings combined with green roofs, depending on the location.

Water footprint and production of rain-fed saffron under different planting methods with ridge plastic mulch and pre-flowering irrigation in a semi-arid region

Most of the saffron cultivation areas in Iran are irrigated and with pre-flowering irrigation being necessary to facilitate flower emergence. However, the growers face shortage of water. Post- flowering rain-fed (PFRF) saffron cultivation could be a solution, and ridge and furrow rainfall harvesting (RFRH) with plastic mulch could be used to collect runoff in the field planting areas. In this regard, the objectives of this study were to determine the effects of interaction of two different saffron planting methods (basin and furrow planting), using plastic mulch and without plastic mulch on ridge of the furrow planting, using irrigation at pre-flowering and without irrigation on saffron growth, yield, yield components, economic water productivity (EWP) and water footprint of saffron in two growing seasons with low (167 mm) and high (367 mm) seasonal rainfall in a semi-arid region. Without irrigation in pre-flowering (NPFI) produced a saffron yield reduction of 70% compared with pre-flowering irrigation (PFI). It is concluded that 90 mm of irrigation water should be applied as PFI for adequate flowering and yield. In addition, the use of the RFRH system resulted in a runoff coefficient of 0.85 and increased soil water storage (48% at low seasonal rainfall), saffron yield (51%), leaf dry matter, LDM (90%) and EWP (17%). The blue water footprint (BWF) with low rainfall (165 mm) was higher than that with abundant rainfall (367 mm), because saffron yield in the second year was lower due to the older age of saffron in field, which resulted in lower yield and consequently higher BWF. Likewise, green water footprint (GWF) was higher (4810 m3 kg−1) than those that obtained as BWF (739 m3 kg−1) due to the fact that pre-flowering irrigation is necessary for onset of flower and the regional rainfall is insufficient to initiate flowering. The effects of low seasonal precipitation (less than 200 mm) on saffron were manifested in yield and LDM reduction of 70% and 42%, respectively, compared to high seasonal precipitation, decreasing as seasonal precipitation increased. Precipitation reached around 300 mm in rain-fed with pre-flowering irrigation caused no reduction in saffron yield and LDM. Therefore, in PFRF conditions, furrow planting with ridge plastic mulch and pre-flowering irrigation is recommended. The economic water footprint of saffron under PFRF conditions with PFI was 50% of that obtained for irrigated saffron production, which is preferable in virtual water trade.

Snowmelt‐Radiation Feedback Impact on Western U.S. Streamflow

AbstractOngoing runoff declines in the Colorado River Basin have been shown to be predominately driven by decreasing albedo from warming‐driven snow‐cover loss, especially in late‐spring (hereafter snowmelt‐radiation feedback). Here, we explore the feedback's impact on annual runoff sensitivity to warming across the western U.S. (WUS) using hydrologic model simulations. For 1°C uniform warming, we show that runoff is most sensitive to warming in modestly snow‐covered, interior mountain headwaters, especially the Rocky Mountains. Runoff sensitivities are most associated with the snowmelt‐radiation feedback in basins with runoff coefficients between 0.2 and 0.6, where runoff sensitivity increases with more snow and lower winter temperature. In aggregate, ∼48% of WUS runoff sensitivity is attributable to the snowmelt‐radiation feedback and is especially pronounced in the warming‐sensitive river basins (annual runoff decreases >5%/°C). We also show that the feedback's impact decreases with increasing temperature, which has unresolved implications for streamflow declines in a less‐snow future.

Evaluating flash flood vulnerability using combined deterministic and parametric model: A case in the upper Ciliwung watershed, Indonesia

On January 19, 2021, a flash flood hit the Upper Ciliwung watershed, a mountainous area in Indonesia, causing damage to seven buildings and displacing 1,800 residents. To minimize the impact of such disasters, there is a need for disaster risk awareness and management specifically focused on flash floods in mountainous regions. Therefore, this study aims to assess the flash flood potential index value in the Upper Ciliwung watershed. The research utilized deterministic (Soil and Water Assessment Tool-SWAT) and parametric (Flash Flood Potential Index-FFPI) modeling to analyze various factors, including slope, geology, ground movement, Antecedent Precipitation Index (API), and Runoff Coefficient (Curve Number-CN). The models showed satisfactory goodness-of-fit statistics with R2 and Nash-Sutcliffe efficiencies (NSE) values of 0.58 and 0.57, respectively. The findings indicated that 39.95% of the watershed had a moderate vulnerability index value of 3, while downstream areas (31.7%) had a low vulnerability index value of 2, and the middle and upstream regions had high vulnerability index values of 4 and 5, covering 23.65% and 2.49% of the total area. These results provide valuable insights to local authorities for implementing measures to reduce the Upper Ciliwung watershed’s vulnerability to flash floods.

The Effect of Land Cover Changes on Surface Runoff Using the Soil and Water Assessment Tool in the Bila Watershed

Changes in land cover have a negative impact on land and water resources that occur in the watershed area. This study aims to analyze changes in land cover in 2016 and 2021 and their effects on surface runoff in the Bila Watershed. Analysis of land cover change using the Geographic Information System approach, and then analyzing the effect of land cover change on surface runoff from the results of the Soil and Water Assessment Tool Model. The results showed that the land cover of Bila Watershed when experiencing the highest change was in shrubs of 680.29 ha, dryland agriculture covering an area of 520.99 ha and secondary dryland forest covering an area of 155.76 ha. The effect of land cover changes on surface runoff varies. The highest increase in surface runoff was in shrub cover change to agricultural land and open land while the lowest increase in surface runoff was with changes in primary dryland forest land cover to secondary dryland forest. The surface runoff coefficient of the Bila Watershed in 2016 was included in the good category with a value of 0.16 while in 2021 was included in the moderate category with a value of 0.26.

Using integrated GIS and hydrological analysis for sizing culverts of multiple channel crossings at the flooded section of the Daboya-Mankarigu Road (IR10) in Ghana

A culvert is an important structure in Road construction to allow the conveyance of Channels crossing the road. Culverts are sized for a road to accommodate the volume of water crossing the road network to avoid flooding. Ghana Highways has a standard manual for culvert sizing at channel crossing. This manual serves as a guide for the proper sizing of culverts, however, lots of culverts have been found to have failed. Among the reasons for the failure of culverts could be under-sizing, urbanization, climate change, lack of maintenance, etc. The Daboya-Mankarigu Road is situated in the Savanah Region of Ghana in the North Gonja District. The section of the road from Chainage 9 + 075 to 10 + 200 has been experiencing flooding from 2020 to 2021 with a flood depth of 3.315 m in 2020 and 2.00 m in 2021. This study seeks to use integrated GIS and hydrological-based methods to propose new culverts to supplement the existing culverts to control flooding at section (9 + 075 to 10 + 200) of Daboya-Mankarigu Road (IR10). Geographic Information system (GIS) model (SWAT), Hydrological and hydraulic models were used to determine the peak flow at the catchment to Propose new culverts to supplement the existing culverts. Using a design period of 25 years for culverts, the modified rational method was used to determine the Peak flow of the catchment. A 25-year peak flow of 367.155 m3/s was determined and used for hydraulic analysis of the existing culverts. From the study, the existing culvert structures at the section had a hydraulic capacity of 78.732 m3/s which could not accommodate the remaining flow of 288.423 m3/s in the catchment. An observation was made that the changes in the rainfall can cause a change in rainfall intensity. An increase in built-up areas in the catchment can also increase the runoff coefficient which can result in higher peak flow in the catchment. Climate change, change in slope, and Land use in the catchment were also determined to have a huge influence on the adequacy of culverts since the peak flow is dependent on these parameters in the catchment as the years go by. A 4No. 4 m × 4 m box culvert, 3No. 3.5 m × 3.5 m box culvert, and 13 No. 1200 mm pipe culverts with 2 each at different chainages were proposed at suitable locations to supplement the existing culverts using the HDS-5 equations in AutoCAD Civil 3D. A recommendation is made to consider the installation of these new culverts at the flood section to control flooding and avoid overtopping of water on the IR10 road section (Daboya-Mankarigu) in the north Gonja District.

Selecting criteria for urban basin delineation based on UAV photogrammetry: a case study in Culiacan, Mexico

Abstract Urban storm drainage is essential for the large part of the population living in cities with torrential rains to protect public urban infrastructure, private property, and human lives from flooding. The most important design parameter for urban storm drainage is the flow discharge, which is normally calculated with the area, runoff coefficient, and rainfall intensity depending on basin delineation. This requires highly accurate topographic information on the urbanized terrain that digital elevation models sometimes do not meet due to the lack of resolution. This study proposes criteria for delineating urban basins considering urbanization without requiring the usual topographic surveys. The proposed basin delineation is based on a high-resolution digital elevation model obtained from an unmanned aerial vehicle (UAV) and field verification of flow directions. As a result, the delineation of two urban basins was obtained: an urban basin within an area that drains exclusively to a sinkhole and another basin that additionally drains out through other points of the divide. The latter basin does not comply with the traditional concept of a hydrological basin because it has more than one outlet. In addition, this basin has an area that is 38% of the total area draining into the sinkhole.

Uncertainty analysis of 100-year flood maps under climate change scenarios

This study presents an assessment of the uncertainty associated with 100-year flood maps under three scenarios: present, RCP4.5, and RCP8.5. Through intensive Monte Carlo simulations, the study focuses on evaluating the uncertainty introduced by key model input parameter, namely the roughness coefficient, runoff coefficient, and precipitation intensity. Notably, the precipitation intensity incorporates multiple sources of uncertainty, including RCP scenario, climate model, and probability distribution function. To analyze the uncertainties, a surrogate hydrodynamic/hydrologic model based on a physical 2D model is employed.The findings of this study challenge the traditional use of deterministic flood maps and climate factors, highlighting the necessity of employing probabilistic approaches for the development of accurate and secure flood maps. Moreover, the research findings indicate that the primary source of uncertainty in precipitation is the selection of the probability distribution, followed by the choice of climate model, and to a lesser extent, the specific RCP scenario.