Soil Conservation Service Method Research Articles

Analysis of land use change on flood discharge of Bengawan Solo Upstream sub-basin

Abstract This study investigated land use changes of Bengawan Solo Upstream sub-watershed impact toward flood discharge between year 2015 and year 2019. The daily rainfall intensity was calculated statistically by using analysis frequency, and effective rainfall was acquired by compensation of potential storage and land use. Runoff discharge was calculated using the Nakayasu and the Soil Conservation Service method, while base flow discharge calculated using equation suggested by Hydrograph Synder Synthetic Gama-1. Land use change is represented by curve number (CN) value for year 2015 and year 2019 at values of 78.11 and 78.07, respectively. Decline of CN value was caused by surge of vegetation land area. Agricultural land CN value was not much different from settlement CN value. Overall, flood discharge that occurred plummeted between year 2015 and year 2019, although it was not significant. Decrease in flood discharge corresponds to decrease in CN value. Decline of CN value as much as 0.05 % yielded decrease of flood discharge as much as 0.16 % until 0.22 % related to return period.

Pengaruh Perubahan Tutupan Lahan Terhadap Karakteristik Hidrograf Banjir (Studi Kasus Bendungan Jragung)

Demak and Grobogan Regency are areas where a flood frequently happen during the rainy season. PUPR Ministry built the Jragung Dam for flood management which was planned using the 1998 - 2017 data series. The Jragung River discharge tends to experience an increase in a period of 10 years, with one possible cause is changes in land cover. Therefore, to determine the effect of land cover changes on the flood hydrograph characteristics of Jragung Reservoir, a flood tracking analysis was carried out in Jragung Reservoir. This study use the HEC-HMS program with the Soil Conservation Service (SCS - CN) method. and the land cover change index used was curve number and impervious. The results of the analysis show that there is a change in land cover in the Jragung Reservoir catchment area of 2,5%, which is dominated by an increase in residential area of 55,6%. As a result of conducted, the Jragung Reservoir catchment all n-year return periods flood discharge has increased from design year (2017) and latest year (2022). QPMF increased from 1586,1 m3/s to 1689,6 m3/s which resulted in an increase in the Jragung Reservoir flood water level from planned QPMF in +118,6 m become +118,7 m.

Application of Dynamic Model for Designing Zero Runoff System to Control Erosion in Cocoa Fields

Land degradation in cocoa plantations is mainly caused by surface runoff erosion. Surface runoff can be reduced by applying a Zero Runoff (ZRO) system. This system effectively reduces runoff when its size sufficiently infiltrates all surface runoff. This study aims to determine the size, dimensions, and location of a ZRO system that effectively increases infiltration and prevents surface runoff. The size and dimensions of the system were designed using a water balance approach, where all surface runoff is collected in the ZRO system and then infiltrated. Surface runoff was calculated using the Soil Conservation Services (SCS) method. The potential infiltration rate is a function of the soil's saturated hydraulic conductivity and the system's surface area. The saturated hydraulic conductivity of the soil was determined using the falling head method. The size and dimensions of the system were determined through model simulation based on field physical condition data using a dynamic model. The research results showed that the size and dimensions of the system depend on the amount of rainfall, the area of the catchment area, and the saturated hydraulic conductivity of the soil. From the dynamic model simulation, all surface runoff will be infiltrated if the dimensions of the zero runoff system are 1 x 1 x 0.5 m. This size can accommodate a water volume between 0 – 0,006 m3, so with a system depth of 1,000 mm, there is no surface runoff.

Enhancing climate-resilient urban river restoration: predictive modeling of geomorphic changes

Abstract Urbanization and climate change are two potent forces shaping the contemporary environment. Urban rivers, integral to city life, are profoundly affected by these dynamics. While restoration efforts have yielded promising results, a persistent challenge lies in the inadequate consideration of geomorphic processes and climate change impacts in restoration planning. This study addresses this critical gap by proposing a novel approach for designing stable urban river geometries in ungauged basins. Leveraging the Soil Conservation Service (SCS) method in conjunction with General Circulation Model (GCM) data, our research focuses on determining design discharge and channel stability. Our principal finding, based on the incorporation of parameters related to precipitation, runoff, and effective discharge, indicates a projected 35% increase in the width of stable urban rivers in the future. These results underscore the urgency of integrating climate change considerations into urban river restoration initiatives. Neglecting this imperative aspect risks the failure of restoration projects, particularly in addressing geomorphic challenges intensified by climate change. This research offers a valuable framework for future restoration efforts, ultimately contributing to the resilience and sustainability of urban river ecosystems.

Quantification of Surface Runoff Using Different Methods (Case Study: Waqf Infiltration Basin in the Gaza Strip)

Background: The surface runoff created by rainfall is essential to recharge the Gaza coastal aquifer with fresh and clean water when adequately collected and infiltrated. Thus, accurate estimation of surface runoff can foretell the actual volume of incoming stormwater to the infiltration basin. Method: There are several methods for calculating rainfall-runoff only a few of them are accurate due to various restrictions and limitations. Rational formula was used to calculate the surface runoff entering Waqf infiltration basin located in Gaza city. Results: The daily surface runoff was estimated as 265,320 m3 using the Rational method while it was 324,000 m3 using the Soil Conservation Service (SCS) method at 67 mm rainfall depth for 5 year return period. Whereas, at 10 mm rainfall depth during the 2021-2022 wet season, a large difference was determined between the two methods. Thus, in-situ estimation was used as a third method, in which the water height in Waqf basin’s grit removal chamber was measured, thereby calculating the daily surface runoff as 360 m3 which was not far from the result obtained by the SCS method at 10 mm daily rainfall depth. Conclusion: It was concluded that using a reliable method was very important for the accurate estimation of surface runoff, which leads to a well-designed infiltration system in the Gaza strip.

PENINJAUAN SISTEM POLDER GROGOL DALAM MENGHADAPI BANJIR

Floods that often occur due to high rainfall inflicts social problems and other social impacts on the community. Therefore. a capable drainage system is necessary which comprises drainage channels with adequate capacities as well as pumps with sufficient capacities and operational rules. The study focuses on hydrological and hydraulical analysis on the system of Polder Grogol, West Jakarta. The estimation of design flood discharge employs Soil Conservation Service method with 5 years return period for Semeru and Makaliwe channels. The results of hydraulical analysis shows both channels are still adequate in draining design flood discharge. However, the existing pumping system is no longer sufficient to keep the reservoir’s water level below the bottom of reservoir’s inlet channel. There are several options to lower the reservoir water level. In this study, the approach is to add a new pump with the capacity of 0,25 m3/s wihout changing the formation of existing pumps. The analysis results reveals the additional pump manages to lower the reservoir water level below the targeted elevation.

STUDI PENERAPAN KONSEP EKO HIDRAULIK UNTUK MITIGASI BANJIR DI SUNGAI PULISAN

The analysis began by finding the frequency of rain using the Log Pearson III method. The rain data used came from two rain posts, namely the Araren-Pinenek MRG rain post and the Maen Climatology rain post. The rainfall data used is the maximum daily rainfall data from 2002 to 2019. Rain flow modeling on the HEC-HMS komputer program using the HSS Soil Conservation Services method, and for water loss with the SCS Curve Number (CN). For baseflow using the recession method. HSS SCS parameter calibration was performed before simulating flood discharge using peak discharge test. The calibrated parameters are lag time, curve number, recession constant, initial discharge and ratio to peak. For the limits of each parameter is adjusted to the standard values in the HEC-HMS komputer program. The peak discharge test results show 2.2 m3 / second. Then a flood discharge analysis was carried out with calibrated parameters using the HEC-HMS komputer program. The peak discharge results simulated each time are re-entered in the HEC-RAS komputer program, then simulating flow profiles including flow velocity and high elevation of the water table. The flood discharge plan used is the 25 years period of 24,5 m3/second by installing several Eco Hydraulic constructions such as vetiver grass, bush grass, bamboo plants, logs, and a combination of vetiver grass and logs. The flow speed of the existing cross-section with the application between vetiver grass and logs can be reduced by 62%. With the use of Eco Hydraulics, it can reduce and optimize flow speed and looks aesthetic considering Pulisan is a superpriority area

FLOOD MODELLING OF RIAM KIWA WATERSHED USING HEC-HMS

At the end of 2021 to early 2022 several areas in Banjar Regency were flooded. This incident had a major impact on the surrounding area and became a national concern. One of the causes of the disaster was high-intensity rainfall which caused the water in the Riam Kiwa River to overflow. HEC-HMS software was used to simulate the designed flood discharge. This research aims to model the magnitude of the designed flood discharge with return periods of 5, 25, 50, and 100 years. Due to limitations of rainfall data from the field, satellite data from GSMaP were collected. In the distribution of rainfall frequency analysis, the Log Pearson type III method was chosen for calculating designed rainfall. Then, the Modified Mononobe Method was applied to calculate hourly rainfall intensity. Other data i.e., soil types, slope gradient and land use were analyzed using ArcGIS application. These three data produced hydrological parameters which were used as input values in the HEC-HMS using the Soil Conservation Service (SCS) method. Three parameters’ values show that Riam Kiwa watershed has more than 90% clay with a slope gradient of 83.58% (steep slope) and land use is predominantly consisted of mixed dryland agriculture (47.73%). From HEC-HMS simulation, it was found that Riam Kiwa watershed with an area of 1781.77 km2 produces maximum flood discharge ranges from 8,822.3 m3/s to 17,058.6 m3/s; with a water volume ranges from 182,991.9 m3 to 340,889.6 m3 in 5 years to 100 years return periods, respectively. From the results, it can be concluded that impermeable clay soil and steep slope are the two major factors that contribute to the flooding occurrence in the area.

Frequency analysis of rainfall events in Karbala city, Iraq, by creating a proposed formula with eight probability distribution theories

ABSTRACT Due to its impact on the derivation of hydrological models and the safe design of sewer and storm networks, the anticipation of rainfall events should be intensively studied. In this regard, studying the rainfall events in Karbala, Iraq, has specific importance after the rapid increase in population in this city and the impact of climate change beyond 2003. Herein, the maximum daily rainfall depth of Karbala city has been analyzed to investigate and extract its probability of future occurrence using frequency analysis. Eight theoretical probability distributions, which are Weibull, Gamma, Gumbel, Log normal, Generalized Extreme Value, Normal, Exponential, and Log-Pearson Type III, were fitted using Hyfran Plus software to simulate the characteristics of the observed probability of rainfall depth. Based on the results of four statistical indicators, the exponential distribution revealed the best performance as compared with other distributions. Accordingly, ‎the synthetic storms of 24 hr were derived‎ for cumulative and incremental distribution of rainfall depth using the Soil Conservation Service method type ΙΙ for the arid and semiarid region to recurrence periods ‎‎(T = 2, 5, 10, 15, 25, 50, 100, 200, and 500), also the rainfall intensity duration frequency curves were developed. As an essential finding, new validated empirical formula has been proposed to optimize the coefficients of the location of Karbala city which may fill the gap for predicting the rainfall intensity and improving storm management strategies in Iraq.

Assessing the Groundwater Recharge with Water Balance in Ameriat Al-Falluja City, Al-Anbar Governorate, Western Iraq

This study aims to figure out how to calculate water recharge using the soil conservation service method, one of the most widely used methods for calculating runoff volume following rainfall. The research is being conducted in Ameriat Al-Falluja City, Al-Anbar Governorate. The Iraqi meteorological organization's Baghdad Airport and Al-Ramadi stations provided data on the research area from 1989 to 2020 as total annual rainfall (123.1 mm), the RH% (43%), the mean monthly T (23.6 °C), total evaporation (3169.61 mm), the wind speed (3.1 m/s), and the sunshine duration (9 h/day). The climate of the study area is described as arid. The total evapotranspiration value quantity is 1137.38 mm for the 32-year comparison period, while the total amount of correct evapotranspiration was 992.3 mm. Water surplus is 36.7% of total rainfall, which equals 45.2 mm. Groundwater recharge is 45.2 mm, with a rate of 36.7%, showing the groundwater recharge (%) from total rainfall. The value of groundwater recharge throughout a year is about equivalent to 23.6848* 105 m3/year.

Analysis of Flood Hydrograph Metro Sub Watershed with Synthetic Unit Hydrograph Snyder and SCS (Soil Conservation Service) Methods

Metro Sub-watershed is in Malang City. Based on data from BPBD Malang City, flood disasters have continued to increase from 2016 - 2022. The purpose of this research is to analyse the synthetic unit hydrograph (SUH) which will be used as the basis for planning water resources management. The rainfall data used in 2012-2021 with an average maximum rainfall height of 108 mm... Metro sub-watershed with an area of 31.371 km2 and a river length of 42 km and land use data with 59% of the residential. All data will be analysed for SUH in return periods Q2 = 2th, Q5 = 5th, Q10 = 10th, Q25 = 25th, Q50 = 50th, and Q100 = 100th. SUH analysis using HEC-HMS auxiliary program with Snyder and SCS (Soil Conservation Service) methods. The peak discharge results of the SUH in the Snyder method are Q2 = 47.8 m3/s, Q5 = 48.6 m3/s, Q10 = 50.7 m3/s, Q25 = 52.8 m3/s, Q50 = 54.1 m3/s, Q100 = 55.2 m3/s, and in the SCS method are Q2 = 37.5 m3/s, Q5 = 37.9 m3/s, Q10 = 39.8 m3/s, Q25 = 41.8 m3/s, Q50 = 43 m3/s, Q100 = 44 m3/s.

Hydrometeorological Data Analysis and Drought Indices of Rawandoz Area, Iraqi-Kurdistan Region

Water balancing techniques are strategies for resolving key theoretic and applied hydrologic challenges. The primary goals of the study are to examine the climatic characteristics and conditions that will be utilized in the water balancing approach used in the Rawandoz located in northeastern Iraq. The meteorological data from Soran meteorological station’s 2000 to 2020 were applied to analyze the climate patterns of the research region. The annual rainfall average is 750.50 mm, while the annual evaporation is 1497.80 mm. The average monthly humidity, temperature, and sunshine remained 73.8 percent, 18.50 °C, and 8 hours/day, respectively. The Kharrufa technique has been calculated the potential evapotranspiration (PET), water deficit and surplus and the Soil Conservation Service method (SCS) has been used to calculate surface runoff (Rs). The annual potential evapotranspiration, water surplus, and deficit are calculated to be 1900.27 mm, 430.10 mm, and 1579.90 mm, respectively, with an annual runoff of 376 mm. The standardized precipitation index (SPI) was produced to assess climatic drought over a variety of duration; the mean value is 0.562, indicating that the area is moist. The results of many climate classification reveal that the study area in humid to moist climate classification.

Multiscenario flood hazard assessment using probabilistic runoff hydrograph estimation and 2D hydrodynamic modelling

In this paper, we aim to define a procedure of flood hazard assessment applicable to large river basins in which flood events can be induced/sustained by the full basin area or by fractions of the total area as functions of the extent of the triggering precipitation event. The proposed procedure is based on a combined approach accounting for (1) the reconstruction of intensity–duration–frequency curves expressing the magnitude in terms of intensity for multiple return periods; (2) the application of the soil conservation service method for runoff estimation from a selected rainfall scenario considering some characteristics of the basin (i.e. soil type, land use/treatment, surface condition, and antecedent moisture conditions); (3) 2D hydrodynamic modelling conducted by the HEC-RAS model using runoff hydrographs as hydrological input data; (4) the reconstruction of flood hazard maps by overlaying multiple inundation maps depicting flood extent for different return periods. To account for the variability in the extent of the triggering precipitation event and the resulting input hydrograph, multiple contributing areas are considered. The procedure is tested at the archaeological site of Sybaris in southern Italy, which is periodically involved in flood events of variable magnitude. The obtained results highlight that the variable extent of the floodable area is strongly conditioned by the extent of the contributing area and return period, as expected. The archaeological site is always involved in the simulated flooding process, except for the smallest contributing area for which only a 300-year event involves this part of the site. Our findings may be useful for developing and supporting flood risk management plans in the area. The developed procedure might be easily exported and tested in other fluvial contexts in which evaluations of multiple flood hazard scenarios, due to the basin geometry and extent, are needed.

Assessment of Hydrological Extremes for Arid Catchments: A Case Study in Wadi Al Jizzi, North-West Oman

The objective of this research was to analyse hydrological variability by conducting an intensive analysis of extreme events, under dry and wet conditions. Drought conditions were assessed using the Standard Precipitation Index (SPI) and Rainfall Anomaly Index (RAI), while the Soil Conservation Service (SCS) method was used to simulate flooding at four stations. The SPI results indicated that the amount of rainfall within the catchment area is near to normal, ranging from 64% to 75%, with some extremely wet exceptions which may cause flash floods. The RAI results also indicated that the amount of rainfall within the catchment area is near to normal, but the extremely wet category obtained the largest percentage (ranging from 36% to 50%) and the very wet category had the lowest percentage (ranging from 9% to 36%). The simulated flooding, using SCS, tended to slightly underestimate the observed streamflow, while the performance showed some weaknesses when the observed flooding was less than 1 m3/s. The Nash–Sutcliffe Efficiency showed higher performance at closer rainfall stations to the outlet, with values of 0.92 and 0.94. Distant stations simulated floods that showed a lower level of efficiency, with values of 0.77 and 0.81. Given the fact that hydrological extremes (dry and wet conditions) are connected, the findings of the two indices and the SCS method are consistent and suitable for monitoring drought and flood events under climate change.

Mapping the risk of flooding of the national road N°2 at the crossing of the wadi Tamdmadt north of the city of Bni Drar

Floods have a significant impact on transport infrastructure, especially the road. The present study aims to assess the risk of flooding of the national road N2 at the crossing of the wadi Tamdmadt north of the city of Bni Drar. The hydrological study is conducted by the Soil Conservation Service (SCS) method using the Hec Hms model based on land use and rainfall data from the reference station. The IBER software, based on the two-dimensional equations of Saint Venant governing the free surface flow, is used for the hydraulic simulation.The results obtained allow the elaboration of a flood risk map in the study area. This study aims to help the local authorities in the prevention of the flood risk and the consideration of the necessary protection actions.

Optimum parametrization of the soil conservation service (SCS) method for simulating the hydrological response in arid basins

The use of the soil conservation service (SCS) curve number (CN) model for estimation of the rainfall excess and the SCS-unit hydrograph (UH) model are common tools for flood studies in arid regions. In this research, we are investigating the capability of these models to simulate flood events in the arid region under the common parametrization provided by the SCS model (SCS-CN, the initial abstraction ratio, λ, and UH theory) and the optimum parameterization for best simulating the hydrologic response. A case study is performed in Al-Lith basin in the west of Saudi Arabia (SA). The study simulates measured rainfall-runoff events in the area using seven scenarios (various SCS-CN estimation methods: least-squares method (CNLSM), asymptotic fitting method (CN∞), SCS-CN tables (CNdesign), and antecedent moisture content CN (CNI, CNII, and CNIII), λ = 0.2 and 0.01, and SCS-UH and UH derived from streamflow data) and a comparison is made between the observations and model results under the common parameterization of the SCS model and parameterization estimated from the Saudi arid environment. The comparison between simulated and observed peak flow and runoff volume of the studied events shows high scatter which is a common feature in arid regions due to the inherent uncertainties in the hydrological processes which are not yet resolved due to the lack of detailed measurements of the rainfall-runoff processes. Statistical analysis showed that λ = 0.01 provides a minimum root mean square error (RMSE) in the peak flow (24.8 m3/s) and the runoff volume (0.31 million m3) with CNLSM obtained by LSM. CN∞ is bad to simulate the hydrologic response. The SCS-CN Tables cannot be used for hydrological simulation. They can rather be used for the design purposes of mitigation structures.

Assessment of a New Dam Site for Water Supply Potential in Bauchi Metropolis, Nigeria

The maximum yield of 90,000 m3 /day from the existing Gubi dam in Bauchi will barely meet the water demand beyond 2030 at an average water use of 100 litres per capita/day. For higher water demand of up to 250 litres per capita/day expected in an urban centre, the existing dam capacity is inadequate, and the demand should grow to 253,102 m3/day by 2037. This is the rationale for this study, which showed the feasibility of a new dam through technical reviews and analysis of topography, hydrology of the site, field and laboratory investigations, computer analyses and designs. Hydrologic simulation of rainfall-runoff processes for 57 years of rainfall data using the Soil Conservation Service (SCS) method gave an annual runoff volume of 59 Mm3 on a stream in Miri, which can be harnessed to assure adequate water supply in the metropolis. This will require the construction of a 25 m high embankment dam. Topographic survey and analysis indicated that the proposed site has good water retention capability. Although net flow adjustment analysis showed a high evaporation loss of up to 13.5 Mm3 annually, seepage loss is expected to be small in view of the underlying basement complex rock formation.

Runoff Curve Number (CN model) Evaluation Under Tropical Conditions

In tropical countries the Curve Number method (CN) of the Soil Conservation Service (SCS) is widely used in civil engineering (to calculate drainage infrastructure) as well as in agricultural and environmental studies. However, little is known about the accuracy of CN method in tropical watersheds. To reveal the CN method accuracy, this study compares the CN method results with field data measured in an Andean micro watershed. For this, CN values for the tropical micro watershed "La Vega" were identified using the tables proposed by the SCS and its respective moisture and slope corrections (CNAMC2S); subsequently CN values were derived from 55 events (CNQ) in which runoff and rainfall were measured. It was observed a different of 27% between CNQ and CNAMC2S (CNQ = 80, CNAMC2S 58.1). According to that, the data shows that in the tropical micro watershed evaluated in this study, the SCS method overestimated runoff. The CN model of the SCS is strongly influenced by the antecedent humidity and its impact becomes stronger after high rainfalls records; however, the antecedent humidity influence was not observed in measured runoff data. Despite the CN – SCS model did not present a relationship between CN and precipitation, this relationship was observed in measure data. This study shows that CN method has some inaccuracies and it requires further studies to know its applicability in tropical conditions.

Impact of roof rain water harvesting of runoff capture and household consumption.

In recent years, the occurrence of floods is one of the most important challenges facing in Hamadan city. In the absence/inefficiency of urban drainage systems, rainwater harvesting (RWH) systems as low-impact development (LID) methods can be considered as a measure to reduce the floods. In this study, three scenarios concerning the RWH from the roof surfaces are studied to evaluate the type of the harvested water on reducing flooding. In the first scenario, which indicates the current situation in the studied area, it is indicated that there is no harvest of the roof surfaces in the studied area. The second scenario is about the use of water harvested from the roof surfaces for household purposes. The third scenario also refers to the use of harvested water for irrigation of gardens. The simulation results of these three scenarios using the Soil Conservation Service (SCS) method in the Hydrologic Modeling System (HEC-HMS) model reveal that if the second scenario is implemented, the runoff volume decreases from 28 to 12% for the return period from 2 to 100 years. However, in the third scenario, this reduction in runoff volume will be 48 and 27% for return periods of 2 to 100 years, respectively. Therefore, the results of this study indicate that the use of harvested water can also affect the reduction on runoff volume.

Urban Rainwater Harvesting Assessment in Sulaimani Heights District, Sulaimani City, KRG, Iraq

Rainwater harvesting is the collection of rainwater and runoff from catchment areas such as roofs or other urban surfaces. Collected water has productive end-uses such as irrigation, industry, domestic, and can recharge groundwater. Sulaimani heights have been selected as a study area, which is located in Sulaimani Governorate in Kurdistan Region, North Iraq. The main objective of this study was to estimate the amount of harvested rainwater form Sulaimani heights urban area in Sulaimani City. Three methods for runoff calculation have been compared, the storm water management model (SWMM), the soil conservation service (SCS) method, and the runoff coefficient (RC) using daily rainfall data from 1991 to 2019. The annual harvested runoff results with the three different methods SWMM, SCS, and RC were estimated as 836,470 m3, 508,454 m3, and 737,381 m3, respectively. The results showed that SWMM method has the highest runoff result and could meet 31% of the total demand of the study area and 28% and 19% for RC and SCS methods, respectively.