Probable Maximum Flood Research Articles

Climate resiliency of a tailings management facility: case study of Mont-Wright mine

ABSTRACT This study investigates the climate resiliency of the Mont-Wright mine tailings management facility (TMF) in Quebec, Canada, with a focus on tailings erosion and flooding. Ultra-high resolution (1 km) climate simulations of the global environmental multiscale (GEM) model, spanning the current (2001–2020) and future (2041–2060) periods, form the basis of this study. Comparison of GEM model outputs against gridded observation data suggests reasonable performance of the model in simulating TMF-relevant climate variables, giving confidence in the model. The analysis indicates potential increases in tailings erosion rates of up to 6% (0.01 g/m2s) for the future period due to elevated wind-induced shear stress. Floods, represented in terms of probable maximum flood, reveal future increases in magnitudes of up to 20% in summer/fall for durations of 12–72 h. Increases of up to 17% are projected for spring for the 72-h duration, with decreases noted for other durations due to precipitation efficiency reductions. The projected small increases in erosion rates, in absolute terms, are not deemed to be of any major concern. As for projected increases in flooding, Mont-Wright mine’s climate-change adaptation strategy, which is aligned with existing Quebec guidelines, seems reasonable to mitigate flooding impacts.

Downstream impacts of dam breach using HEC-RAS: a case of Budhigandaki concrete arch dam in central Nepal

Studies on concrete dam breach are limited compared to earthen and other types of dams. With an increase in the construction of concrete dams, particularly in the developing world, it is imperative to have a better understanding of the dam breach phenomena and the identification of the most influential breach parameters. This study aims to contribute to this gap by taking the case of the concrete arch dam proposed for the 1200 MW Budhigandaki Hydropower Project located in central Nepal. This study carries special significance for Nepal, primarily because of the increasing number of under construction and proposed large dams for water resources development in the country. We carry out dam breach analysis of the Budhigandaki dam using HEC-RAS 2D model to calculate the flood discharge peaks, time to peak, water surface elevation and the extent of inundation for two scenarios (with and without probable maximum flood) to estimate the damage on four downstream settlements. We carry out sensitivity analysis of the breach parameters on the flood magnitudes and severity. Results show that all the study locations lie in the high flood hazard zone. Flood peaks can reach as high as 286,000 m3s− 1 to 511,000 m3s− 1 in the considered settlements. The time to peak ranges from 11.3 to 17 h after the breach at these locations. We estimate that if a breach should happen, it would most likely inundate around 150,000 buildings, impact nearly 672,000 lives and flood 3,500 km of road downstream. Furthermore, dam breach elevation is found to be the most sensitive parameter to downstream floods. Hence, rather than structural measures, it is recommended that non-structural measures are implemented for minimizing the impacts of flood disasters at the study locations. The findings could be a useful reference for future dam projects in Nepal and other areas with similar hydrological and topographical conditions.

Stability analysis of an unreinforced concrete gravity dam

This project involved undertaking a stability analysis of an unreinforced concrete gravity dam. The stability assessment considered the 1 in 10 000 year and probable maximum flood events as well as the effects of ice and seismic loading, concluding that the above-ground dam section did not meet modern factors of safety and that further works would be required to stabilise the dam.

Analisis Hujan Ekstrim Probable Maximum Precipitation (PMP) menggunakan metode Hersfield dan Perhitungan Debit Banjir

Extreme rain is rain with the lowest intensity of 50 mm/24 hours or 20 mm/hour. River is an elongated surface water flow and flows from a higher place (upstream) to a lower place (downstream). The area of KIuet is 1429.93 km and the area of Kluet River is 163.51 km2 and the length of the river is 68.26 km. The problem is that Kluet Utara River experiences high rainfall, resulting in overflows that flatten agricultural land and submerge residential areas. The purpose of the study was to calculate the planned return period rainfall, analyze the PMP (probable Maximum Precipitation) value and analyze the flood discharge to evaluate the PMF (Probable Maximum Flood) value and the return flood discharge. The benefits of this research are used to see the PMF value and return period rainfall to analyze the frequency of flooding KIuet Utara Watershed (DAS). The scope of the research was to calculate rainfall and flood discharge in KIuet Utara Watershed and secondary data which includes 10 years rainfall data obtained from BMKG (Meteorology, Climatology and Geophysics Agency) Indrapuri Aceh Besar and watershed maps obtained from PT. Mediatama Indoconsult. Processing of rainfall data on return period used Log Pearson III Method and PMP used Hersfield Method while calculating the planned flood discharge using Melchior Method. The results of the research is the rainfall value for the return period for the lowest rainfall in the 2 year return period is as high as 211,836 mm and the highest rainfall for the 1000 year return period is 566,239 mm, so that the flood discharge plan for the return period for the lowest flood discharge in the 2 year return period is equal to 2061,342 m3/s and the highest flood discharge at the 1000 year return period is 5510,490 m3/s. The PMP value was obtained at 2128,432 mm so that the PMF was obtained at 20714,772 m3/s. Log Pearson III and PMP methods can be used to calculate the rainfall in KIuet Utara and the results from the rainfall are used to calculate the planned flood discharge using Melchior Method.

Assessing dam spillway discharge capacity in response to extreme floods in Perak river hydroelectric scheme: Simulation and proposed mitigation measures

The aged dams in Perak river Hydro-Electric Scheme (HES) have been constructed decades ago and a common concern raised during dam safety reviews is that they were not designed to safely reroute the Probable Maximum Flood (PMF) but rather the Inflow Design Flood (IDF) of 1,000 years’ design floods. Failure due to the insufficient spillway discharge capacity has been identified as one of the primary causes leading to overtopping. This applied research has thus been initiated to evaluate the spillway discharge capacity of dams in response to PMF extreme flooding. Besides, the safety of the dams has been evaluated by calculating the highest flood level achieved in response to the specified extreme floods. In order to simulate PMF hydrographs, various durations of Probable Maximum Precipitation (PMP) have been calculated using Hershfield statistical approach based on historical annual maximum rainfall statistics. Using a calibrated and validated hydrological model developed in HEC-HMS, PMF simulation was performed. It was discovered that the PMF generated at 120 hrs (5 days) resulted in the maximum flood level for all dams/reservoirs. The achieved highest PMF flood levels are still lower than the designated dam core and crest level in respective dams, indicating that the dams in Perak river HES are safe from overtopping failures during the occurrences of extreme events up to PMF level. While routing the worst-case scenario over 120 hr, the maximum spillway discharges predicted for Temengor and Bersia are beyond their design capacity, while Kenering and Chenderoh remain within design limits. Mitigation that will be implemented to minimize the possibility of risks to occur include improvement of emergency management system and dams monitoring data collection. It is anticipated that the outcomes of this applied research will be adopted for development of Risk Informed Decision Making (RIDM) frameworks for dams in Perak river HES in future.

Study on the Evolution of Tailings Dam Break Disaster under Complex Environment

In response to the challenges posed by rapid development, the wide-ranging disaster impact, and the untimely warning of debris flow resulting from tailing dam failure, it is of great significance to study the mechanism of dam failure as well as the evolution law and affected area of debris flow for effective disaster prediction and risk assessment. We developed a 1:150 physical model for testing tailing dam failure and combined it with RAMMS (V1.7.0) debris flow software to investigate the mechanisms of tailing dam failure and the evolutionary patterns of rock flows in complex environments. Through the analysis and comparison of experimental data, we comprehensively summarized the consequences of disaster risk resulting from dam failure. The results show that the grain size distribution of the model sand should be moderate; the composition of the particle size distribution has a significant impact on the collapse morphology of the dam after failure. The saturation line is the lifeline for the stability of the wake reservoir, and its level determines the degree of saturation of the wake in the reservoir. The breach was at the midpoint of the crest of the dam. The inflow volume at the time of the breach was 0.313 m3. According to the flow ratio relationship, the inflow volume at breach occurrence was equivalent to 1.78 times the total amount of a 1000-year flood and 1.19 times the total amount of a probable maximum flood (PMF). Analysis of the surface flow field revealed that the region with the highest flow velocity extended from the toe of the dam to Shangdi village; the impact on the village of Shizhou was limited to the backflow of the dam break and the gradual sedimentation of the tailings.

Dam breach analysis of Kibimba Dam in Uganda using HEC-RAS and HEC-GeoRAS

Dam failures have severe consequences on human life and property. In the case of an earth filled Kibimba Dam located in Eastern Uganda, the occurrence of a flood equal to or larger than the probable maximum food (PMF) could result in catastrophic economic losses including loss of human life. This study utilized the USACE Hydrologic Engineering Center's River Analysis System (HEC-RAS) and Hydrologic Engineering Center’s Geographic River Analysis System (HEC-GeoRAS) to analyze the potential dam break of Kibimba Dam, considering overtopping and piping failure scenarios. The results of the analysis revealed that the spillway of Kibimba Dam possesses sufficient capacity to safely discharge a flood resulting from a probable maximum flood peak of 400 m3/s. Therefore, the dam is not susceptible to breach under the overtopping failure mode. However, the dam failed under the piping failure mode. To assess the downstream impact of the dam break, the breach hydrographs resulting from piping failure were examined. Consequently, the study investigated the effects of flood propagation downstream of the dam. This resulted in varying inundation depths of up to 6 m and velocities ranging from 1.2 to 10 m/s. These findings highlight the devastating consequences of Kibimba Dam's failure, particularly affecting rice field plantations, infrastructure, and other economic activities in the downstream area. Therefore, the outcomes of this study are crucial for the development of Emergency Action Plans that incorporate dam breach and flood routing analyses specific to the affected downstream regions.

Flood modelling and its impacts on groundwater vulnerability in sub-Himalayan region of Pakistan: integration between HEC-RAS and geophysical techniques

Hydropower projects play a pivot role in the development of a country. Constructions of reservoirs create job opportunities and provide cheap energy but at the same time cause several environmental issues. The current study utilizes geoelectric and flood modelling data to develop a relationship between flood scenarios and their effect on river flows in association with the vulnerability of groundwater due to hydroelectric projects on Neelum River, Pakistan. The resistivity data delineated local aquifer systems that comprised both confined and unconfined aquifers ranging from 05 to 48 m depth, having poor to weak protective capacity with good groundwater development potential. The flood zonation models indicate a decline in the flow rate of the Neelum River from 317 to 39 m3/s with a drop in stage and flow velocity that contributes to a high risk of leachate penetration in the poorly protected shallow aquifer. The aquifer systems that mostly lie near the banks of the river face a serious threat of contamination due to low river flow. The flood modelling revealed that in case of dam burst, maximum probable flood will affect the land cover of 30,43,250 m2 and 33,64,433 m2 in Muzaffarabad and Patikka areas, respectively, affecting major population.

A Study on Dam Break Simulation considering Continuous Rainfall Events

In recent years, flood damage resulting from continuous rainfall events has been on the rise. However, existing Emergency Action Plans (EAPs) addressing reservoir or dam failure only consider Probable Maximum Precipitation (PMP), which represents a single rainfall event. This study aims to address this limitation by simulating a dam break scenario caused by continuous rainfall events. The Chungju dam watershed was selected as the study area and a mega rainfall event scenario, involving continuous 500-year frequency rainfall intensity events, was defined. Next, the flood discharge resulting from the mega rainfall event scenario was estimated using the Consecutive Storm Event Based (ConSEB) model. The Simplified Dam Break (SMPDBK) model was employed to simulate the dam break. The flood discharge estimated for this scenario amounted to 31,080.34 cms, which is about 1.2 times larger than the Probable Maximum Flood (PMF). The dam break water level simulated by the SMPDBK model was 150 m and the flood damage area was estimated to be 307.45 km2. Based on the results of the study, we highlighted the need to consider continuous rainfall events within EAPs.

Estimation of Probable Maximum Flood by Flood Frequency Analysis at Tiuni Barrage Site on River Tons

Estimation of Probable Maximum Flood by Flood Frequency Analysis at Tiuni Barrage Site on River Tons

Estimating Typhoon-Induced Maximum Flood for Spillway Safety Assessment—Case Studies in Taiwan

Dam safety assessment is usually conducted regularly to investigate the risks associated with the dam and propose remedies to ensure effective reservoir operations. One crucial aspect of the evaluation involves performing hydrological analyses to determine if the existing spillway can successfully deliver the probable maximum flood (PMF) downstream. This study applied storm transposition and typhoon rainstorm methods for PMP estimations. The resulting PMP values were then used as input for runoff models to generate flood hydrographs for PMF determination. A modification for the storm transposition method was proposed to determine the barrier height considering the moisture inflow direction. In estimating the orographic rainfall in the typhoon rainstorm model, an effective terrain slope was suggested according to different windward directions based on DEM analysis. Shihmen Reservoir and Feitsui Reservoir, located in northern Taiwan, were used as examples to conduct the PMP and PMF analysis. The obtained PMPs were further compared with the results generated by Hershfield’s method to assess the reasonability of the estimation. The results show that the maximum deviation of the 24-h PMP values estimated by the three methods is within 30% in the Shihmen watershed and 16% in the Feitsui watershed. The PMF estimations in the two reservoir watersheds are larger than the design discharges of the existing spillways. Hence, extending the capacity of the existing spillways or constructing upstream bypasses to avoid catastrophic flooding downstream is required.

Probable maximum flood: the potential for estimation in the UK using ReFH2

Abstract The current reservoir safety guidance within the UK recommends the use of the FSR/FEH rainfall-runoff model to estimate PMF (probable maximum flood) peak flows for reservoirs within the highest risk category (A). However, the FSR/FEH model has been superseded by the ReFH2 rainfall-runoff model for all other flood risk purposes in the UK. This study develops a new modelling framework for PMF estimation using ReFH2 by translating the assumptions made within the current FSR/FEH PMF procedure and applying these within the ReFH2 rainfall-runoff model. Peak flows from the methodology are compared with those from the FSR/FEH model for 400+ catchments. The study highlights the potential for ReFH2 to be used as the rainfall-runoff model for all return periods, up to and including the PMF, thereby paving the way for using the ReFH2 model for reservoir safety studies.

Assessing the effects of increased impervious surface on the aquifer recharge through river flow network, case study of Jackson, Tennessee, USA

Understanding pathways connecting urbanization to the recharge process across the land surface and river environment is of great significance in achieving low-impact development. Accordingly, the contribution of an urbanized region with a low and high development rate, along with the expected overflow into the river network resulting from increased impervious surfaces, was assessed in the recharge rate at Jackson, Tennessee. To this end, first, the losses were calculated using the standard and modified SCS-CN methods for the maximum probable flood condition. Then, TUFLOW was applied to simulate the two-dimensional flood for a historic 24-h probable maximum precipitation event with a 100-year return period. The results of TUFLOW were later calibrated using the results of standard and modified SCS-CN methods. A calibrated MODFLOW was employed to assess the effects of urbanization and, consequently, the plausible extended river network on the recharge rate. Results revealed that the West Wood contribution in groundwater recharge was 19 % less than the Musa Street, while it supplies approximately 2.7 % more flow than Musa Street. The performance evaluation results of TUFLOW showed 0.4916 and 0.689 as Nash–Sutcliffe, respectively, for the standard and modified SCS-CN methods. Although the flow velocity and depth were respectively increased by 3.3 % and 8.3 % under modified SCS-CN compared to the standard one, the soil water storage capacity remained constant at equal to 0.16 mm. Results revealed that the maximum soil water storage capacity was fulfilled soon through the modified SCS-CN than the standard method leading to higher flood volume and discharge. To this end, the discharge resulting from modified SCS-CN was approximately 1.5 times higher than that in the standard method under the same precipitation condition. Our findings suggest that designing any construction, mainly dams downstream, based on the modified SCS-CN estimations will provide more safety, particularly in crowded regions. Also, overflowing the excess surface runoff into the river network resulted from the increased impervious surface amplifying the flow volume, depth, and velocity across the river networks, finally leaving the area without increasing the aquifer's recharge rate. The results provide insights into possible sustainable development options and flood management in the built-up area.

Determination of Clark unit hydrograph parameters for estimating probable maximum flood

Abstract The probable maximum flood (PMF) is the flood caused by the probable maximum precipitation (PMP). A unit hydrograph (UH) is generally used to derive the PMF for the given PMP, but a method is needed to modify the UH parameters to reflect the PMP condition. This study presents a new method using the estimated channel velocity to modify the Clark UH parameters under the ordinary condition into those under the PMP condition. This study considers major dam basins in Korea and evaluates the application results in comparison to several previous studies. As application results of the proposed method, the Clark UH parameters under the PMP condition are found to be within the range 39–53% of those under the ordinary condition, with their mean of about 44%. The UH derived by applying this mean ratio shows that its peak time and the peak flow are just 44 and 227% of the UH under the ordinary condition, respectively. This change from the ordinary condition to the PMP condition is more extreme in Korea than that in Australia and the United Kingdom. This extreme change seems to be due to the climate in Korea, located in the Asian Monsoon region.

Hydrological and Hydrodynamic Modeling for Flash Flood and Embankment Dam Break Scenario: Hazard Mapping of Extreme Storm Events

Simulation of dam breach scenarios can help in the preparation of emergency action plans for real dam breaks or flash flooding events. The purpose of this study was to identify flood-prone areas in the Al Wala Valley in the governorate of Madaba in Jordan through analysis of the Al Wala Dam. Modelling of dam breaches was conducted under two scenarios: a Clear Day scenario and a Probable Maximum Flood (PMF) scenario. The former scenario does not address the various dam failure modes; rather, it addresses the formation and development of a breach as a result of structural failures like the sliding of dam blocks in the case of a concrete dam or piping failures in the case of embankment dams. The PMF scenarios, however, simulate unsteady flow in pipes and overtopping failure via consideration of runoff hydrography. In the PMF scenario, flood-prone areas can be identified by in-depth analysis of data from previous extreme rainfall events. The related hydrologic and hydraulic data can then be modelled using intensity-duration-frequency curves applied to an hour-by-hour simulation to discover the areas most at risk of flooding in the future. In the present study, data were collected from inlet of flow to Al Wala Valley on 10 January 2013. The collected data, which included rainfall and discharge data, were fed to the HEC-HMS software in order to calibrate the hydrological parameters of the watershed of the Al Wala Dam. Additionally, the HEC-RAS tool was employed to determine the breach outflow hydrography and hydraulic conditions across various critical downstream locations, which were determined by use of dynamic flood wave-routing models. The simulations revealed that, in the case of the Clear Day scenario, downstream inundation would cover an area of 5.262 km2 in the event of a pipe failure. However, in the event of a six-hour storm, a twelve-hour storm, and a twenty-four-hour storm, the flooded area would rise to 6.837 km2, 8.518 km2, and 9.390 km2, respectively. In the event of an overtopping failure, 13.171 km2 would be inundated, according to the Clear Day scenario. On the other hand, in the event of a six-hour storm, a twelve-hour storm, and a twenty four-hour storm, the flooded area would rise to 13.302 km2, 14.249 km2, and 14.594 km2, respectively.

Hydrological Analysis of Batu Dam, Malaysia in the Urban Area: Flood and Failure Analysis Preparing for Climate Change

Extensive hydrological analysis is carried out to estimate floods for the Batu Dam, a hydropower dam located in the urban area upstream of Kuala Lumpur, Malaysia. The study demonstrates the operational state and reliability of the dam structure based on hydrologic assessment of the dam. The surrounding area is affected by heavy rainfall and climate change every year, which increases the probability of flooding and threatens a dense population downstream of the dam. This study evaluates the adequacy of dam spillways by considering the latest Probable Maximum Precipitation (PMP) and Probable Maximum Flood (PMF) values of the concerned dams. In this study, the PMP estimations are applied using comparison of both statistical method by Hershfield and National Hydraulic Research Institute of Malaysia (NAHRIM) Envelope Curve as input for PMF establishments. Since the PMF is derived from the PMP values, the highest design flood standard can be applied to any dam, ensuring inflow into the reservoirs and limiting the risk of dam structural failure. Hydrologic modeling using HEC-HMS provides PMF values for the Batu dam. Based on the results, Batu Dam is found to have 200.6 m3/s spillway discharge capacities. Under PMF conditions, the Batu dam will not face overtopping since the peak outflow of the reservoir level is still below the crest level of the dam.

HYDROLOGICAL PREDICTION FOR MAPPING THE POTENCY OF BREAK IN THE SAGULING DAM, WEST JAVA PROVINCE, INDONESIA

Dams are structures built across bodies of water to hold the water back. They offer various economic, environmental, and social benefits, including large-scale water storage, hydroelectric power generation, tourism, and recreation. However, in addition to offering benefits, dams are also associated with certain risks. One of the biggest risks is the possibility of a dam breaking, which may occur if the discharge inflow is overly high at the point it enters the reservoir. A very high discharge inflow can result in a probable maximum flood (PMF) discharge. This study investigates the potential of hydrological analysis with regard to mapping the dam break potency of the Saguling Dam in Indonesia. The reservoir system on the Citarum River consists of three reservoirs, namely Juanda (Jatiluhur), Cirata, and Saguling. Together, they comprise a cascade reservoir system. The Saguling Dam is located in the upstream, the Cirata Dam is in the middle stream, and the Juanda Dam is under the Cirata Dam. This study focuses on the Saguling and Cirata Dams. It analyzes the PMF using the Nakayasu, ITB-1, Gama-2, and Snyder methods. Moreover, the rainfall analysis involves the Thiessen polygon and the frequency distribution of the Gumbel, Log Pearson-III, and Log Normal, while the hourly rainfall is analyzed using the PSA-7 currently being investigated in Indonesia. The intensity of the rainfall in the catchment area of a dam is directly related to the level of the discharge inflow that enters the reservoir. The Saguling Dam faces a similar risk, which explains the need to conduct a comprehensive hydrological analysis to assess and map one of the key risk factors for the dam breaking.

Estimation of probable maximum precipitation 24-h (PMP 24-h) through statistical methods over Iran

Abstract Estimating the probable maximum precipitation (PMP) is necessary to calculate the probable maximum flood (PMF). It is of high importance in checking the adequacy of dam overflow capacity and other development and water transfer plans of a given area. In this research, using the for an annual 24-hour maximum rainfall data set of 45 synoptic stations throughout the country, the PMP values were calculated through the original Hershfield method and then the Hershfield-Desa method. By comparing the obtained results of 24-hour PMP estimation through the two mentioned methods, it is found that the estimation of PMP values in the original/first Hershfield method is well higher than the expected value (2.54 to 4.03). While in the modified method (Desa method), PMP values are significantly reduced and seem more reasonable (1.02 to 1.3). Meanwhile, the calculated variability and skewness coefficients also indicated more variability of PMP values in the southern stations of the country compared to rainy regions, which makes the estimation of PMP in the southern regions of the country considerably unreliable.

Dam Break Analysis using HEC-RAS: A Case Study of Karjan Dam

A dam is a structure constructed across river which stores water and supplies water for various purposes. Though the dams have many benefits, there is always a threat of dam break floods which are devastating in nature. Hence it becomes essential to analyze and simulate dam failure scenarios to understand the severity of dam break flood and identify areas under threat which helps in land use planning and developing emergency response plans. This study attempts to carry out dam break/breach analysis for the Karjan dam using a two-dimensional hydraulic model called Hydraulic Engineering Center’s River Analysis System (HEC-RAS). RAS-Mapper tool is used to extract river geometry data from the Cartosat-1 digital elevation model (DEM) and to generate the inundation map to identify the areas affected. The study involves the prediction of breach parameters, breach flood hydrograph, peak flow, flood arrival time, and generation of inundation maps. The dam break model is simulated for unsteady flow conditions using Probable Maximum Flood (PMF) corresponding to different failure scenarios. HEC-RAS tool is utilized to determine the breach outflow hydrograph and hydraulic conditions at critical downstream locations. The outcome will assist the local government in making proper planning and development decisions. Key Words: Arc-GIS, Dam break analysis, Karjan dam, Flood Inundation, HEC-RAS

Estimation of Probable Maximum Flood for Dam Safety in Cameron Highlands Watershed

Dams that are not designed to withstand major storms may be destroyed and increase the flood damage opportunities downstream. For protecting the lives and land downstream of Cameron Highlands, Malaysia, the current research targeted to estimate the Probable Maximum Precipitation based on the updated rainfall and other meteorological data and predict the Probable Maximum Flood using the Hydrological Model (HEC-HMS) version 4.8. The Geographic Information System was utilized as well in order to identify the geometric and hydrologist parameters. The PMP data is obtained up to 2020 via the application of Hershfield’s Statistics and by applying the model mentioned earlier, the Probable Maximum Precipitation values can be predicted. For the calibrating the model, different sets of data were applied in which the Nash-Sutcliffe Efficiency and Percentage of Bias of 0.776 and -0.03% respectively are obtained while Nash-Sutcliffe Efficiency and Percent Bias of 0.861 and 1.47% respectively are obtained for Cameron Highland dams for model validation. The hydrological model in this study was adequately calibrated for Probable Maximum Flood simulation as it is credible to describe the hydrological process in Cameron Highlands.