Estimated Peak Discharge Research Articles

Snyder Unit Hydrograph and GIS for Estimation of Flood for Un-Gauged Catchments in Lower Tapi Basin,India

In the flood prone catchments, it is needful to estimate the discharge, standard lag time, time of peak, and flood response of each watershed in the basin. The SUH method offers considerable advantage over others, and thus, has been chosen for estimation of flood response, contribution of flooding potential, percentage of flood volume for 25 sub-watersheds. The discretion of sub-watershed for estimation of peak discharge, time of peak, alternate lag time, and width of SUH at 50% and 75% of peak found to offer advantages over other methods. This paper considers Snyder Unit Hydrograph (SUH) with GIS based spatial database for calculating discharge at Lower Tapi Basin (LTB). The hydrological parameters of each sub-watershed such as river length, length of centroid, spatial area, land use, lateral slope, and terrain and soil factors have been extracted from GIS database. The geo-data has been combined with topographical maps to produce a digital elevation model (DEM) of 50 m cell size. The analysis for all 25 subwatersheds exhibit that 35.07 m3/s and 4.55 m3/s and 13.23 hours and 4.33 hours have been highest and lowest peak flow and time of peak respectively. The SUH model has been validated for peak discharge at a gauge site Amli (E73023' N21023') where discharge data were collected during 2010 and 2011 monsoon. A comparison between measured and SUH modelled discharge shows good fit within a mean variability range of 5-7%. The SUH methods ability to estimate hydrological parameters including peak flow discharge shows wider replication for un-gauged catchments.

Review of current methods for estimating areal reduction factors applied to South African design point rainfall and preliminary identification of new methods

Design point rainfall estimates assume a uniform distribution of rainfall over a catchment, and hence are only representative for a limited area. For larger areas, areal reduction factors (ARFs) are used to convert design point rainfall depths/intensities to an average areal design rainfall depth/intensity for a catchment-specific critical storm duration and catchment area. This paper presents a review of ARF estimation methods used nationally and internationally, with comparisons of the South African methods in the C5 secondary drainage region using standard input variables. The comparison of different ARF estimation methods confirmed that the empirical methods adopted for general use in South Africa are based on a limited database of observed rainfall data and are used without local correction factors beyond their original developmental regions. This results in the characterisation of the actual rainfall process over a catchment, and translation into questionable design peak discharge estimates. Therefore, the ARFs in South Africa need to be re-investigated in the light of recent extreme flood events, utilising the longer periods of record and denser rain-gauge networks which are now available for analysis. The variation of ARFs with return period and with rainfall producing mechanisms also needs to be investigated. Updated ARFs developed and verified using local rainfall data will improve the accuracy of design hydrology for large catchments in South Africa when event-based rainfall-runoff deterministic methods are used.

Lower Rhine historical flood magnitudes of the last 450 years reproduced from grain-size measurements of flood deposits using End Member Modelling

ObjectiveThe objective of this research was to unlock the potential of fluvial archives to create flood chronologies, based on grain-size characteristics of flood deposits located in two recently formed fluvio-lacustrine sequences. MethodsGrain-size data was compared with contemporaneous discharge measurements (for the Lower Rhine, The Netherlands). Regression relations between coarse-tail grain-size parameters and measured discharge were established for the last ~240years, and applied to the older parts of both cores – resulting in peak discharge estimates back to AD ~1550. ResultsGrain-size descriptive parameters such as the 95th percentile and end-member modelling outcomes correlate well with discharge and turn out to be sensitive proxies for inferring flood magnitudes. Locally, geomorphological changes influence the relation between peak discharge magnitudes and flood bed coarseness, but these can be assessed, using continuous flood layer and background sedimentation measurements to standardize grain-size descriptive parameters. Conclusion/implicationsFlood records distilled from sedimentary archives hold great potential for extending existing records of observed discharge and aid establishment of design discharge for flood protection measures and assessment of non-stationarity of the flooding regime due to climatic and anthropogenic forcing.

Do we still need the Rational Formula? An alternative empirical procedure for peak discharge estimation in small and ungauged basins

The Rational Formula is the most applied equation in practical hydrology due to its simplicity and the effective compromise between theory and data availability. Although the Rational Formula has several drawbacks, it is reliable and surprisingly accurate considering the paucity of input information. However, after more than a century, the recent progress in computational ability, theory and large-scale monitoring compel us to try to suggest a more advanced yet still empirical procedure for estimating peak discharge in small and ungauged basins. In this paper, an alternative empirical procedure is described and discussed, and then a discussion as to whether the Rational Formula is still necessary is presented. The presented methodology integrates the three standard steps of the common event-based approach (design hyetograph, rainfall excess and rainfall–runoff transformation) accurately adapted for application with a lack of observed data. The proposed procedure requires the same input information as necessary for application of the Rational Formula (soil properties, intensity–duration–frequency rainfall curves and Tc) and provides both the peak discharge and the design hydrograph shape and, most importantly, reduces the subjectivity of the hydrologist in its application.Editor D. Koutsoyiannis

Monthly discharge forecasting using wavelet neural networks with extreme learning machine

Accurate and reliable hydrological forecasting is essential for water resource management. Feedforward neural networks can provide satisfactory forecast results in most cases, but traditional gradient-based training algorithms are usually time-consum- ing and may easily converge to local minimum. Hence, how to obtain more appropriate parameters for feedforward neural networks with more precise prediction within shorter time has been a challenging task. Extreme learning machine (ELM), a new training algorithm for single-hidden layer feedforward neural networks (SLFNs), has been proposed to avoid these disadvantages. In this study, a conjunction model of wavelet neural networks with ELM (WNN-ELM) is proposed for 1-month ahead discharge forecasting. The a trous wavelet transform is used to decompose the original discharge time series into several sub-series. The sub-series are then used as inputs for SLFNs coupled with ELM algorithm (SLFNs-ELM); the output is the next step observed discharge. For comparison, the SLFNs-ELM and support vector machine (SVM) are also employed. Monthly discharge time series data from two reservoirs in southwestern China are derived for validating the models. In addition, four quantitative standard statistical performance evaluation measures are utilized to evaluate the model performance. The results indicate that the SLFNs-ELM performs slightly better than the SVM for peak discharge estimation, and the proposed model WNN-ELM provides more accurate forecast precision than SLFNs-ELM and SVM.

ESTIMATION OF LAG TIME AND PEAK DISCHARGE OF FLASH FLOOD OF WADI SUDR IN THE SINAI PENINSULA

Environmental protection of residential areas from flash flood hazard necessitates the prior estimation of peak discharge and lag time. Thus estimation of flash flood hydrograph at a watershed outlet is essential for hydrologic flood control design and warning system design and operation. Lag time and peak discharge are the most important parameters that affect the flash flood hydrograph estimation. Hydrological models employ many different equations to calculate these parameters. This paper concerns to calculate losses parameters using measurement data of rainfall and runoff hydrographs of Wadi Sudr, Sinai, Egypt. Then watershed modeling system WMS is applied using all available lag time equations and adjusted losses parameters. In addition, peak discharge is estimated using the equations of SCS dimensionless synthetic unit hydrograph. The output hydrograph of these equations is compared to field data in order to propose the best equations to calculate runoff hydrograph. The output results indicate that there is no optimal method to calculate both of lag time and peak discharge in the study area. As a result, dimensional analysis is used to develop a new lag time and peak discharge equations of Wadi Sudr using the measured data of different storms. The developed equations enable the prediction of the lag time to an accuracy of 7% error and peak discharge to an accuracy of less than 14% error which enables Wadi Sudr to be environmentally protected from flash flood hazards

Estimation of peak discharges of historical floods

Abstract. There is no doubt that the hazard assessment of future floods, especially under consideration of recent environmental change, can be significantly improved by the consideration of historic flood events. While flood frequency inventories on local, regional and even European scale have already been developed and published, the estimation of their magnitudes indicated by discharges is still challenging. Such data are required due to significant human impacts on river channels and floodplains, though historic flood levels cannot be related to recent ones or recent discharges. Based on experiences from single local key studies, we present the general outline of an approach to estimate the discharge of the previous flood based on handed-down flood level and topographic data. The model for one-dimensional steady flow is based on the empirical Manning equation for the mean flow velocity. Background and potential sources of information, acceptable simplifications and data transformation for each element of the model equation are explained and discussed. Preliminary experiences regarding the accuracy of ±10% are documented, and potential approaches for the validation of individual estimations are given. A brief discussion of benefits and limitations, including a generalized statement on alternative approaches, concludes the review of the approach.

Review of methods used to estimate catchment response time for the purpose of peak discharge estimation

Large errors in peak discharge estimates at catchment scales can be ascribed to errors in the estimation of catchment response time. The time parameters most frequently used to express catchment response time are the time of concentration (TC), lag time (TL) and time to peak (TP). This paper presents a review of the time parameter estimation methods used internationally, with selected comparisons in medium and large catchments in the C5 secondary drainage region in South Africa. The comparison of different time parameter estimation methods with recommended methods used in South Africa confirmed that the application of empirical methods, with no local correction factors, beyond their original developmental regions, must be avoided. The TC is recognized as the most frequently used time parameter, followed by TL. In acknowledging this, as well as the basic assumptions of the approximations TL = 0.6TC and TC ≈ TP, along with the similarity between the definitions of the TP and the conceptual TC, it was evident that the latter two time parameters should be further investigated to develop an alternative approach to estimate representative response times that result in improved estimates of peak discharge at these catchment scales.Editor Z.W. Kundzewicz; Associate editor Qiang Zhang

Improving the flood prediction capability of the Xinanjiang model in ungauged nested catchments by coupling it with the geomorphologic instantaneous unit hydrograph

Summary Improving the predictive capabilities of rainfall-runoff models in ungauged catchments is a challenging task but has important theoretical and practical significance. In this study, we investigated the predictive capabilities of the conceptual Xinanjiang model (XAJ), which is widely used for flood forecasting and simulation in China, in ungauged catchments. We further produced a hybrid rainfall-runoff model (named XAJ-GIUH) by coupling the XAJ model with the geomorphologic instantaneous unit hydrograph (GIUH) to achieve improved flood predictions in ungauged catchments. The flood prediction capabilities of the original XAJ model and the XAJ-GIUH model were investigated and compared at an hourly time scale in a mountainous catchment with six nested catchments located in the south of Anhui province, China. The two models were first calibrated for each individual catchment by comparing with the observed streamflows. Then, the nested catchments were treated as ungauged and modeled using the parameter values regionalized by transposition from the downstream catchments. The results show that the performance of both models is comparable and satisfactory on different catchment scales in the case that model parameters are calibrated in each catchment. However, the models perform differently in the case that model parameters are transposed from the downstream catchments. The XAJ-GIUH model produced markedly improved estimates of peak discharge and peak time as compared to the original XAJ model in the latter case, indicating that the runoff routing is a major uncertainty source for the application of the XAJ model in this case. Coupling XAJ with topography-based GIUH has the potential to substantially improve the flood prediction capability of the XAJ model in ungauged catchments. Our analysis further reveals that the models do not necessarily perform better when the parameter values are transposed from closer donor catchment. Instead, adopting the parameter values from the catchment with more similar topographic characteristics is more likely to produce better model performance. This study implicates the necessity of including remotely sensed geomorphologic characteristics of ungauged catchments to improve flood predictions in these regions.

Reconstructing peak discharges of historic floods of the river Ahr, Germany

In the presented paper, peak discharges of historic floods in urbanized areas of different cities on the River Ahr in western Germany are reconstructed based on documentary sources from pre instrumental and the early instrumental period (1804–1937). Maximum water levels of five floods are denoted by flood-marks, with one of these events additionally documented by old photographs. The main challenge is the reconstruction of historic floodplain conditions and modifications influencing the cross-section area and the hydraulic roughness. In order to overcome this problem, a simple approach to estimate peak discharges of historic floods has been applied to the River Ahr. This approach includes a procedure for reconstructing the hydraulic parameters of the river channel and overflooded areas, coupled with an approach for the verification of estimated peak discharge reliability. Five reconstructed discharge maxima are presented. One of these events is well documented by numerous photographs, taken at different times of day, which allow the reconstruction of a hydrograph peak. The validation of the technique by comparison with recent gauged floods reveals results of adequate accuracy. The results show that reconstructed historic floods were partially larger than any gauged flood of the River Ahr.

The Nahal Oz Reservoir dam-break flood: Geomorphic impact on a small ephemeral loess-channel in the semi-arid Negev Desert, Israel

The Nahal Oz Reservoir — in the coastal, semi-arid southwestern Israel was designed to enhance local irrigation of crops using reclaimed sewage water during the dry summer months. On March 2001, part of the western dike of the reservoir was breached and generated a flow release of 3.5∗106m3 of secondary irrigation water that was channeled down the 1st order ephemeral loess stream (Nahal Yare'akh). The consequent 12-hour flood surge, with an estimated peak discharge of 1000m3s−1, inflicted severe loess erosion, agricultural, property and infrastructural damage downstream ($6million).Post-flood mapping documented the geomorphic response to the flood which included channel scour and widening along the initial 2km downstream of the reservoir where a spillway channel was formed. The increase in the cross-sectional area was about 60% and had an estimated 170,000m3 of sediment bed, bank and floodplain erosion. Calculated maximum shear stress and stream power along this section are estimated at 300Nm−2 and 900 wm−2, respectively. The peak discharge at the end of this segment was estimated at 800m3s−1 indicating only minor attenuation along this segment. Two km downstream of the breach, a wide braided fan indicated deposition of the eroded sediments. At the end of this segment the floodwater diverged into several watercourses and inundated tilled agricultural fields and neighborhoods. Downstream, 9km from the reservoir, the discharge attenuated to 100m3s−1, slightly above bankfull. Further downstream and upon reaching the large Shikma stream the flow was already very low. This reduction in discharge is attributed to the anthropogenic infrastructure — roads, neighborhoods and agricultural fields and the large transmission losses typical of sandy ephemeral streams.The study shows that channels within erodible materials respond to high peak discharges very locally. Erosional thresholds that severely incised the channel are only maintained for 2km below the breached reservoir and as distance from the source area increases, available energy is substantially reduced due to high transmission losses, gentler valley gradients, very wide shallow flow and the ability of the drainage network to accommodate large discharges. Consequently, the geomorphic impact was limited to the first 2.6km with only minor erosional or depositional evidence downstream. The current natural flow regime has only minor impact on the newly formed channel geometry below the breached dam. Accordingly, the channel geometry may be preserved for a relatively long time. However, channel recovery in this segment was rapid and within a few years all bare loess surfaces exposed during the flood have been covered by dense vegetation. The analysis also shows that Nahal Oz Reservoir's dam-break flood transmission losses and flood attenuation rates were extreme in comparison to other case studies. This artificial flood event in a desert environment offers a rare opportunity to quantify channel and bank erosion evolution processes during an extremely high-magnitude flood within highly erodible fine sediment as well as to detect the recovery processes a few years later.

Estimation of Peak Flood Discharge for an Ungauged River: A Case Study of the Kunur River, West Bengal

Due to unavailability of sufficient discharge data for many rivers, hydrologists have used indirect methods for deriving flood discharge amount, that is, application of channel geometry and hydrological models, for the estimation of peak discharge in the selected ungauged river basin(s) in their research/project works. This paper has studied the estimation of peak flood discharge of the Kunur River Basin, a major tributary of the Ajay River in the lower Gangetic plain. To achieve this objective, field measurements, GIS technique, and several channel geometry equations are adopted. Three important geomorphic based hydrological models—manning’s equation, kinematic wave parameter (KWP), and SCS curve number (CN) method—have been used for computing peak discharge during the flood season, based on daily rainfall data of September, 2000. Peak discharges, calculated by different given models, are 239.44 m3/s, 204.08 m3/s, and 146.52 m3/s, respectively. The hydrograph has demonstrated the sudden increase with heavy rainfall from the 18th to the 22nd of September, 2000. As a result, a havoc flood condition was generated in the confluence zone of Ajay and Kunur Rivers. This hydrograph might be not only successful application for flood forecasting but also for management of the lower Ajay River Basin as well as the downstream area of Kunur Basin.

Estimation of Instantaneous Peak Discharge Using GIUH, Snyder, SCS and Triangular Models: a Case Study of Central Alborz Watershed

The estimation of instantaneous peak discharge is important for watershed management because there is ainsufficient climatic and hydrologic data in countries such as Iran. Researchers have been forced to link constantparameters (geomorphology) and variable parameters (hydrology) to models with minimum dependence on climaticand hydrologic data for hydrologic estimation. The present study used a synthetic unit hydrograph at three drainagebasins in the central Alborz watershed (Kan, Amameh and Mehran) and compared the results with peak discharge inthe study areas to derive the best model. The results of the instantaneous peak discharge estimation were similar foreach drainage basin. A comparison of the models using relative mean error (RME) and root of mean square error(RMSE) for the three drainage basins showed that the mean RME for GIUH was 21.31, for Snyder was 82.25, forSCS was 227.34, and for triangular was 231.27. The mean RMSE for GIUH was 12.76, for Snyder was 17.05, forSCS was 42.84, and for triangular was 43.62. This confirms that the best estimation was produced by GIUH,followed by the Snyder, SCS and triangular models.

Estimation of Runoff, Peak Discharge and Sediment Load at the Event Scale in a Medium‐Size Mediterranean Watershed Using the Annagnps Model

AbstractIn this paper, the Annualized Agricultural Non‐Point Source (AnnAGNPS) model has been used to estimate runoff, peak discharge and sediment load at the event scale in a Mediterranean watershed. The study area is the Carapelle torrent, Southern Italy (area = 506 km2), where continuous rainfall, streamflow and sediment load data are available. Nineteen flood events have been registered in the period 2007–2009 and were used for the application of the model.The aim of the paper is to evaluate the predictive accuracy of the model at the event scale, in a medium‐size watershed, given the specific conditions of the semi‐arid environments. A sensitivity analysis has been carried out to assign the correct parameterization: the mean normalized output variation of the most meaningful input parameters pointed out the influence of the curve number on runoff, peak discharge and sediment load predictions (values greater than 1); the MN Manning's roughness coefficient and K, C and P factors of the universal soil loss equation showed a moderate influence on sediment load simulations (values between 0·5 and 1).The selection of the Soil Conservation Service synthetic storm types has been based on the observed storm events analysis to improve the peak discharge simulations. The model prediction has proved to be good for runoff (R2 = 0·74, NSE = 0·75, W = 0·92) and peak discharge (R2 = 0·85, NSE = 0·70, W = 0·94), and satisfactory for sediment yield (R2 = 0·70, NSE = 0·63, W = 0·91). The relative error is lower for high events; this result is quite interesting in semi‐arid environments, where most of the annual sediment yield is concentrated in a few, severe events. Copyright © 2013 John Wiley & Sons, Ltd.

Estimating design floods based on the critical storm duration for small watersheds

The objective of this study was to propose a new method to determine design floods using the critical storm duration concept. Five different models, including the Rational, SCS, and Clark methods, were used to estimate peak discharges, while the uniform distribution, Mononobe, Huff, and Yen and Chow methods were applied for the determination of temporal rainfall distribution. Two small watersheds, Baran (HP#6) and Banweol (WS#1), for which watershed hydrologic data were available since 1996, were selected as the study areas. A total of 41 rainfall events was chosen from the study watersheds to calculate peak runoffs and evaluate the performances of the selected hydrological models based on the statistics of RMSE, Nash efficiency criterion (NEC), and R2 value. The Clark method performed the best overall among the selected models, with both NEC and R2 values greater than 0.95. The Huff method resulted in the longest critical storm duration, which was much greater than the times of concentration. The increase in the recurrence interval decreased the critical storm duration while increasing the peak flow rates. The SCS model estimated the greatest design floods, 94.2 m3/s for HP#6 and 56.4 m3/s for WS#1, with a 25-year return period. The design floods for the study watersheds that were estimated by the selected hydrologic models ranged from 68.3 to 132.1% of those estimated by the Rational method. The greatest to the smallest peak flows resulted from the SCS, WFRP, Clark and Nakayasu methods in order. As an alternative to the Rational method, the WFRP method may be appropriate for rural watershed areas in Korea, where paddy fields commonly exist, whereas the SCS model may be more suitable for urban areas, where most land surfaces are covered with impervious material. It was concluded that the incorporation of a critical storm duration concept can contribute to the advance of design flood estimation method in Korea.

Return Period Adjustment for Runoff Coefficients Based on Analysis in Undeveloped Texas Watersheds

The rational method for peak discharge (Qp) estimation was introduced in the 1880s. The runoff coefficient (C) is a key parameter for the rational method that has an implicit meaning of rate proportionality, and the C has been declared a function of the annual return period by various researchers. Rate-based runoff coefficients as a function of the return period, C(T), were determined for 36 undeveloped watersheds in Texas using peak discharge frequency from previously published regional regression equations and rainfall intensity frequency for return periods T of 2, 5, 10, 25, 50, and 100 years. The C(T) values and return period adjustments C(T)/C(T=10 year) determined in this study are most applicable to undeveloped watersheds. The return period adjustments determined for the Texas watersheds in this study and those extracted from prior studies of non-Texas data exceed values from well-known literature such as design manuals and textbooks. Most importantly, the return period adjustments exceed values currently recognized in Texas Department of Transportation design guidance when T>10 years.

Historic floods in the city of Prague – a reconstruction of peak discharges for 1481–1825 based on documentary sources

The paper aims to reconstruct peak discharges of historic floods in an urbanized area of the historic city of Prague based on documentary sources from pre-instrumental and the early instrumental period (1481–1825). Approximately 20–30 maximum water levels are denoted by flood-marks, accounts describing or related at unchanged sites, or by early instrumental measurements. The challenge in this reconstruction is the identification and consideration of man-made floodplain modifications influencing the cross-section area and the hydraulic roughness. In order to overcome this problem, a simple approach to estimate peak discharges of historic floods has been developed and applied to the River Vltava. This approach includes a procedure for reconstructing the hydraulic parameters of the river channel and inundated floodplain, coupled with an approach for the verification of estimated peak discharge reliability. As a result of the different hydraulic characteristics associated with ice jam floods all winter-flood events are excluded to avoid their potential inclusion. We present 18 reconstructed discharge maxima. The validation of the technique by comparison with the recent gauged flood of 2002 reveals results of adequate accuracy. The comparison also shows that the flood event of 2002 was conspicuously greater than all calculated summer floods in 1481–1825.

Evaluation of several techniques for estimating stormwater runoff in arid watersheds

Several traditional techniques have been used for estimating storm-water runoff from ungauged watersheds. Some of these techniques were applied to watersheds of Rashadia in south-eastern desert of Jordan. When engineers apply rainfall-runoff models for hydrologic design, there are difficulties in defining and quantifying peak discharges that are required to design different types of hydraulic structures. The lack of data presents major difficulties for rainfall-runoff modeling in arid regions. These regions have characteristically high rainfall intensity and consequent flash floods. The specific objectives of this study are: (1) apply synthetic hydrographs for estimating peak discharges from limited hydrological data. (2) Evaluate the reliability of six techniques to accurately estimate storm-water runoff; and, to evaluate the runoff that is required to design hydraulic structures such as bridges, culverts and dams. (3) Estimate the flood resulting from direct runoff after subtracting all the loses such as: the infiltration, interflow and evaporation. (4) Develop a simple regression relationship between peak flow discharges and catchment areas. The results show that there is uncertainty in determining the accuracy of storm-water volume, this is due to several methods were utilizing the estimation the hydrographs base time, but promising results in predicting the peak flow discharge.

Extreme flood response to short-duration convective rainfall in South-West Germany

Abstract. The 2 June 2008 flood-producing storm on the Starzel river basin in South-West Germany is examined as a prototype for organized convective systems that dominate the upper tail of the precipitation frequency distribution and are likely responsible for the flash flood peaks in Central Europe. The availability of high-resolution rainfall estimates from radar observations and a rain gauge network, together with indirect peak discharge estimates from a detailed post-event survey, provided the opportunity to study in detail the hydrometeorological and hydrological mechanisms associated with this extreme storm and the ensuing flood. Radar-derived rainfall, streamgauge data and indirect estimates of peak discharges are used along with a distributed hydrologic model to reconstruct hydrographs at multiple locations. Observations and model results are combined to examine two main questions, (i) assessment of the distribution of the runoff ratio for the 2008 flash flood and how it compares with other less severe floods; and (ii) analysis of how the spatial and temporal distribution of the extreme rainfall, and more specifically storm motion, controls the flood response. It is shown that small runoff ratios (less than 20%) characterized the runoff response and that these values are in the range of other, less extreme, flood events. The influence of storm structure, evolution and motion on the modeled flood hydrograph is examined by using the "spatial moments of catchment rainfall". It is shown that downbasin storm motion (in the range of 0.7–0.9 m s−1) had a noticeable impact on flood response by increasing the modeled flood peak by 13%.

Regional model for peak discharge estimation in ungauged drainage basin using GIUH, Snyder, SCS and triangular models

Due to the importance of instantaneous peak discharge estimation for watershed management study in countries like Iran, the search is ongoing to correlate geomorphologic and hydrologic parameters to present models. This paper describes the use of synthetic unit hydrograph at drainage basin of Mehran (Joestan River). The obtained results were compared with recorded peak discharge in outlet of watershed. The models of Relative Mean Error (RME) and Root of Mean Square Error (RMSE) in drainage basin in central Alborz watershed were compared with each other. The results indicate the RMEs of 20.43, 40.06, 133.082, and 135.72, and RMSEs of 16.08, 14.65, 25.37 and 25.82 for GIUH, Snyder, SCS and Triangular models respectively. The daily peak discharge model was derived by 177 recorded events of daily peak discharge. Key words: Peak discharge, parameter, model, Mehran Basin.