Geomorphologic Instantaneous Unit Hydrograph Research Articles

Hydrological Simulation Study in Gansu Province of China Based on Flash Flood Analysis

The calibration and validation of hydrological model simulation performance and model applicability evaluation in Gansu Province is the foundation of the application of the flash flood early warning and forecasting platform in Gansu Province. It is difficult to perform the simulation for Gansu Province due to the fact that it covers a wide range, from north to south, with multiple climate types and diverse landforms. The China Flash Flood Hydrological Model (CNFF) was implemented in this study. A total of 11 model clusters and 289 distributed hydrological models were divided based on hydrology, climate, and land-use factors, among others. A spatiotemporally mixed runoff method and the Event-Specific Geomorphological Instantaneous Unit Hydrograph (GIUH) were applied based on large-scale fast parallel computation. To improve model calibration and validation efficiency, the RSA method (Regionalized Sensitivity Analysis) was used for CNFF model parameter sensitivity analysis, which could reduce the number of model parameters that need to be adjusted during the calibration period. Based on the model sensitivity analysis results, the CNFF was established in Gansu Province to simulate flood events in eight representative watersheds. The average NSE, REQ, and ET were 0.76 and 0.73, 9.1% and 12.6%, and 1.2 h and 1.7 h, respectively, in the calibration and validation period. In general, the CNFF model shows a good performance in multiple temporal and spatial scales, thus providing a scientific basis for flash flood early warning and analysis in Gansu Province.

Morphometric properties, scaling laws and hydrologic response of the Greater Paris combined sewer system

AbstractMorphometric properties of channel networks are useful tools to classify catchments and calculate their hydrological response. Scaling laws have been established for Optimal Channel Networks (OCNs), which are defined based on a generative geomorphological mechanism of minimizing the total energy dissipation. However, sewer networks obey engineering efficiency rules and are conceived based on local optimizations, both in time and space, for minimal costs. Not all the scaling laws have been verified for artificial sewer networks found in urban areas. This raises questions regarding the applicability of OCN scaling laws to sewer networks and their potential impact on the shape of the Geomorphological Instantaneous Unit Hydrograph (GIUH). Hence, this work aims to study the morphometric properties of the Greater Paris combined sewer system through a case study on twelve nested subcatchments. A two‐step methodology is used. First, the morphometric properties are analysed using the reference Horton‐Strahler, Rodríguez‐Iturbe and Moussa‐Bocquillon scaling laws. The results show that Horton‐Strahler's laws of bifurcation are verified while the length and area laws are not always verified. Rodriguez‐Iturbe and Moussa‐Bocquillon laws are verified with slightly different values of the descriptors in comparison to OCNs. Second, these morphometric properties are used to calculate four GIUHs: the reference Width Function (GWF), the Nash unit hydrograph (GN) using Horton‐Strahler ratios, the Nash Unit Hydrograph equivalent (GNe) using Moussa‐Bocquillon descriptors, and the Hayami function (GH) solution of the diffusive wave equation. We identified four catchments for which the scaling laws are verified and therefore all GIUHs are similar while for four other catchments the scaling laws are not verified and strongly impact the GIUHs. These morphometric descriptors and the GIUHs can be considered as ‘hydrological signatures’ of Combined Sewer Systems (CSSs) and are useful for the comparison and classification of hydrological responses.

Factors influencing calibration of a semi-distributed mixed runoff hydrological model: A study on nine small mountain catchments in China

Study Region: Nine mountain catchments (5 in northern and 4 in southern China).Study Focus: Flash floods in small mountain catchments are some of the most frequent and most destructive natural disasters of China. Mixed runoff hydrological model is a popular method for flood warning and forecasting. However, the key factors affecting runoff components in hydrological model parameter calibration need to be further studied. In this study, four different overland flow routing techniques are implemented into a semi-distributed mixed runoff hydrological model system (MRHMS), which are the triangle unit hydrograph (TUH), geomorphological instantaneous unit hydrograph (GIUH), geomorphoclimatic instantaneous unit hydrograph (GcIUH) and kinematic wave (KW). MRHMS-KW is the previously developed spatiotemporally-mixed runoff (SKBY) model.New hydrological insights for the region: The study finds that sensitivity parameters of the MRHMS in northern and southern China are related to their main runoff components. Different parameter orders in automatic calibration of MRHMS result in different model performances, and the suggested parameter orders are consistent with the sensitivity of parameters in northern and southern China. Soil moisture and primary runoff components in northern and southern China differ significantly. Only MRHMS-GcIUH can achieve similar performance in northern and southern catchments. MRHMS-GcIUH therefore enhances our understanding of runoff formation mechanisms in the heterogeneous hydroclimatic landscape of China and is a promising tool for a nationwide flood prediction and flood warning system.

Runoff Characteristics based on Geo-morphological Instantaneous Unit Hydrograph over Humid Region of Himalayas of Bhutan

It is critical to quantify runoff that would be generated due to rainfall in a catchment which would in turn help in predicting the nature of response from a catchment that can be used to come up with a strategic planning and implementation to prevent from certain foreseen or unforeseen calamities. Most of the sub-catchments in Bhutan are un-gauged, which results in the insufficient hydrological data for validating the accuracy of any hydrological model. The current study is approached with identification of reliable hydrological model with the help of real data obtained through customized gauging stations developed using Arduino chip that works on batteries, using sonar sensors. To overcome the issue of insufficient data sets, Om chu river, situated at Phuentsholing is chosen to be gauged for the study. This practical approach towards the analysis of intensity and response of catchment, would help engineers to foresee the possible calamities if any and design the structures accordingly with the reasonable costing. Key Words: quantify, runoff, catchment response, ungauged, hydrological models, arduino

Evaluation of the Velocity Parameter Estimation Methods in a Geomorphological Instantaneous Unit Hydrograph (GIUH) Model for Simulating Flood Hydrograph in Ungauged Catchments

Evaluation of the Velocity Parameter Estimation Methods in a Geomorphological Instantaneous Unit Hydrograph (GIUH) Model for Simulating Flood Hydrograph in Ungauged Catchments

Flood forecasting methods for a semi‐arid and semi‐humid area in Northern China

AbstractThe Double‐Excess (DE) model is a flood forecasting model which was developed to reflect the characteristics of runoff generation in semi‐arid and semi‐humid areas. However, the empirical unit hydrograph used in the subbasin confluence module often has low precision because of the difficulty associated with parameter quantification. This study improves the subbasin confluence module of the DE model by coupling the geomorphologic instantaneous unit hydrograph (GIUH) to establish the improved DE model (DE‐GIUH) to calculate the subbasin confluence based on topographic physical characteristics. The improved model is applied to the Wangjiahui Hydrological Station Basin in Northern China. Compared with the conventional DE model and the widely used hydrologic modelling system (HEC‐HMS) model, the results show that DE‐GIUH improved flood forecasting, including the component peak discharge, flood peak appearance time and flood progress. The qualified rate (QR) of all three models reached grade A (QR ≥ 85.0%). However, the proportion of the deterministic coefficient (DC) reaching grade B or above (DC ≥ 0.70) improved from 50% (HEC‐HMS) and 30% (DE) to 90% (DE‐GIUH) in the calibration period, and from 62.5% and 25% to 75% in the validation period. In particular, for large and medium floods, the proportion of DC reaching grade B and above is 100% for DE‐GIUH, which is much higher than that of the other two models. The proposed improved model provides an alternative method for flood prediction in ungauged areas.

Evaluating performance dependency of a geomorphologic instantaneous unit hydrograph-based hydrological model on DEM resolution

The digital elevation model (DEM) is a type of model that has been widely used in terrain analysis and hydrological modeling. DEM resolution influences the hydrological and geomorphologic features of delineated catchments and consequently affects hydrological simulations. This study investigated the impacts of DEM resolution on the performance of the XAJ-GIUH hydrological model, a model coupling the widely used Xinanjiang (XAJ) hydrological model with the geomorphologic instantaneous unit hydrograph (GIUH), in flood simulations in small and medium-sized catchments. To test the model performance, the model parameters were calibrated at a fine DEM resolution (30 m) and then directly transferred to the simulation runs using coarser DEMs. Afterwards, model recalibration was conducted at coarser DEM resolutions. In the simulation runs with the model parameters calibrated at the 30-m resolution, the DEM resolution slightly affected the overall shape of the simulated flood hydrographs but presented a greater impact on the simulated peak discharges in the two study catchments. The XAJ-GIUH model consistently underestimated the peak discharges when the DEM resolution became coarser. The qualified ratio of peak simulations decreased by 35% when the DEM resolution changed from 30 m to 600 m. However, model recalibration produced comparable model performances when DEMs with different resolutions were used. This study showed that the impact of DEM resolution on model performance can be mitigated by model recalibration to some extent, if the DEM resolution is not too coarse.

The Influence of Two Different Time of Concentration Equations on the GIUH-based Flood Hydrograph Estimates of Keduang and Temon Sub-Watersheds, Indonesia

Understanding the rainfall-runoff response on a watershed requires the study of both the observed and synthetic unit hydrographs. The application of a synthetic unit hydrograph for an ungauged watershed is the prospective alternative. Model development to obtain the unit hydrograph without rainfall and runoff data requires information on the physical characteristics of the watershed and its geomorphological parameters. This paper presents the results of a study on the application of the Geomorphological Instantaneous Unit Hydrograph (GIUH) model in which the time of concentration equations of Kirpich and Ventura were used as a comparison. The study objects are the Keduang and Temon Sub-watersheds of the Upper Bengawan Solo River, Indonesia. The study utilized the sub-watershed characteristic data obtained from the satellite data of ASTER Global DEM V3, which was then processed with the Watershed Modeling System and ArcMap. The results show that in the Keduang Sub-watershed, the Ventura equation gave results closer to the observed unit hydrograph than the Kirpich equation. In the Keduang Sub-watershed, the differences between the two times of concentration on the triangular parameters were significant, i.e. 77.13%, 337.57%, and 338.20% for peak discharge, peak time, and base time, respectively. On the other hand, in Temon Sub-watershed, the differences were 33.88%, 28.63%, and 25.09% for peak discharge, peak time, and base time, respectively. In terms of the GIUH-based flood hydrograph estimation, the results show that the utilization of the Ventura equation generally led to better estimates (closer to the observed flood hydrograph) than that of Kirpich equation.

The Event-specific Geomorphological Instantaneous Unit Hydrograph (E-GIUH): The basin hydrological response characteristic of a flood event

In the field of hydrology, the Geomorphological Instantaneous Unit Hydrograph (GIUH) is central to describing a watershed response. The application of GIUH is extended to individual hydrological events by accounting for the influence of rainfall spatial distribution. A method is proposed herein to identify the Geomorphological Instantaneous Unit Hydrograph specific to each flood event (i.e. E-GIUH), when runoff of effective rainfall is the dominant process. The E-GIUH is derived from observational data, namely: rainfall field time series, and a hydrograph. Such an identification process is formulated as an inverse problem with parameters such as the E-GIUH velocity and coefficient of dispersion, as well as the hyetograph of rainfall excess. The proposed method is applied to several flood events across two mountainous catchments within the Cevennes-Vivarais Mediterranean Hydrometeorological Observatory territory prone to flash flooding. Results indicate that the E-GIUHs display significant variability over the two basins, and the E-GIUH parameters appear to be correlated with the flood event magnitude. The E-GIUH synthetizes the basin response to rain forcing and can be considered as a signature of flood events. A sensitivity study suggests that E-GIUH identification is fairly robust, even with respect to the a priori hyetograph of effective rainfall.

Morphological-hydrological relationships and the geomorphological instantaneous unit hydrograph of Makkah Al-Mukarramah watersheds

The present study focused on developing the predominant relationships between morphological and morphological-hydrological parameters of watersheds in the Makkah Al-Mukarramah region, Kingdom of Saudi Arabia (KSA). These relationships are essential for flood mitigation studies in the region. The relationships developed in this study are averaged over 43 watersheds (varying in size from 42.2 to 6081.4 km2) to provide a theoretical basis for regional morphological and hydrological analyses. In addition, the similarity of the hydrologic response of these watersheds is studied via the theory of geomorphological instantaneous unit hydrograph (GIUH). The results show that there is a relatively high similarity among the 43 basins (the average similarity parameter is 0.61, and the values vary from 0.57 to 0.68 at 95% confidence). Comparisons of the peaking factor between the Soil Conservation Service (SCS) and the Arid-Zone, Ari-Zo, (Albishi et al., Arabian Journal of Geosciences 10:1–13, 2017) models show that the common SCS model underestimates the peak discharge. The time of concentration is overpredicted by the Kirpich (Civil Engineering 10:362, 1940) equation (up to 17 times) compared to the Ari-Zo model. The GIUH and SCS models overestimate the time to peak when compared with the Ari-Zo model. These results are crucial for flood estimation and mitigation in the region.

Mitigation of Scour Failure Risk of a River Bridge Located in an Ungauged Basin

In this study, scour failure risk of the Çatalzeytin Bridge located in the Western Black Sea Basin, Turkey, was assessed for possible future flood events and appropriate scour countermeasures were considered based on economic and constructability considerations. Waterway adequacy in the spans of the bridge and scour criticality around bridge foundations considered for risk calculations in HYRISK were estimated by hydrological and hydraulic analyses of the watershed and stream. Since the watershed of the bridge is ungauged, geomorphological instantaneous unit hydrograph concept was adopted to estimate the peak discharges with various return periods to be used in hydraulic modelling. Monte Carlo simulation results indicated that most of the simulated peak discharges were in the 95% confidence interval. Hydraulic model results from HECRAS indicated that waterway adequacy and scour criticality were critical for discharges with 200 and 500-year return periods. Scour failure risk of the Çatalzeytin Bridge was classified as high and it was proposed to reduce the risk by constructing partially grouted riprap as the most feasible alternative that would consequently increase the expected lifespan of the bridge. Following this methodology, river bridges may be prioritized based on the risk analysis.

Simulating Flash Floods in Small Rivers of the Northern Caucasus with the Use of Data of Automated Hydrometeorological Network

Examples are given for numerical modeling of rain-induced flash floods in mountain areas based on actual and forecast data on precipitation. The calculated hydrographs are compared with the data of hydrometeorological network and calculations of other authors. Two hydrological models were applied: STREAM 2D CUDA, based on numerical solution of the shallow water equations in a two-dimensional (horizontal) formulation using an original algorithm, and KW-GIUH―a Geomorphological Instantaneous Unit Hydrograph model, based on kinematic wave equation. The direct numerical simulation of level regimes at the passage of flood wave and the incorporation of the accumulation of a part of flood flow by reservoirs–traps in the dynamic regime are new scientific results in hydrology. It is concluded that both models can be effectively used to forecast rain floods, in case reliable data on precipitation are available.

Estimation of watershed width function: a statistical approach using LiDAR data

Terrain variability and channel network characteristics critically influence the hydrologic response of watersheds. Width function represents this response under idealized flow conditions of constant velocity and absence of losses, and can be estimated solely using the terrain data. However, the width function, in its graphical form, is less tractable for further analytical applications such as in the derivation of link-based geomorphological instantaneous unit hydrograph. In this study, we systematically redress these issues in the following manner: (a) develop a framework for the functional estimation of width functions using a mixture of truncated skew-normal distributions that captures a wide variety of distribution shapes, (b) provide a basis for model selection based on the Bayesian Information Criterion, (c) demonstrate the utility of a functional estimation approach by identifying hydrologically similar watersheds based on divergence measures applied to the width function estimates, and (d) illustrate the utility of efficient statistical estimation of geomorphic functions and metrics, which affords data reduction and can be scaled to very-large terrain datasets.

Effect of the stream extraction threshold on the morphological characteristics of arid basins, fractal dimensions, and the hydrologic response

This paper presents the effect of the threshold (S) used in the extraction of the stream network on the morphological characteristics, fractal dimensions, and the hydrologic response of arid basins. Four basins with areas vary between 252 and 2726 km2 are considered as a sample in Makkah Al-Mukarramah region, Saudi Arabia (SA). Three different values of the threshold are used for each basin: 0.5 km2, 1.0 km2, and 2.0 km2. The methodology estimated the fractal dimensions of the mainstream and the stream network of the basins based on Horton-Strahler ratios and compared them with measurements from GIS software using the box-counting technique. Two theoretical procedures were used to compute the fractal dimensions. The fractal dimension of the mainstream (d2) is closer to the measured (d) when compared to (d1). Both d1 and d2 overestimated the d values. In contrast, the fractal dimension of the stream network (D1) is closer to the measured (D) values when compared to D2. Both D1 and D2 overestimated D. The values of d range between 1.05 and 1.13 while the D values range between 1.36 and 1.71. Based on the theory of geomorphological instantaneous unit hydrograph (GIUH), it has been shown that the GIUH varies depending on the threshold. The computed GIUH parameters for different thresholds showed that the values of the peak discharge (qp) varies between 0.46 and 1.96 (1/hour) and the values of time to peak (tp) varies between 0.28 and 1.11 hour. The comparison between observed and estimated storm hydrographs of the gauged Dara basin showed high variability with different thresholds. The relative error (RE) in peak discharge (Qp) varies between 0 and 59%. While the RE in runoff volume varies between −7.9% and −58.4%. The RE in lag time (Tlag) varies between 6.3% and −275%. The GIUH based on gamma distribution seems not to be a representative model to the hydrographs in arid regions and other models should be investigated. A new approach has to be followed to develop a GIUH that does not depend on the threshold or finding an appropriate threshold that can be used for accurate flood predictions.

Variability of the geomorphometric characteristics of Makkah Al-Mukaramah basins in Saudi Arabia and the impact on the hydrologic response

Statistical analyses are performed on the geomorphological characteristics of Makkah Al-Mukaramah basins. The purpose of these analyses is to study the variability of the geomorphological characteristics (13 parameters) and their effects on the variability of the hydrological and kinematic response (6 variables). Different probability density functions (PDF) of the prevailing morphometric variables are tested. The Kolmogorov–Smirnov test is utilized for the goodness of fit test to find the best PDF together with Akaike Information Criterion to assess various best fits. The statistical analyses revealed that the highest coefficient of variation (CV = 1.43) is for peak discharge of the geomorphological instantaneous unit hydrograph (GIUH). Apparently, this is due to the high CV (1.14) for the length of the highest order stream. The lowest CV(0.07) is observed for the similarity parameter of basins. This indicates a high similarity between the basins from the geomorphological point of view. The PDF analyses show that the morphological and hydrological variables display different probability distribution patterns. Based on the geomorphoclimatic instantaneous unit hydrograph GCIUH, it has been shown that there is a high variability in the basin response as a result of an exponential distribution of rainfall intensity and duration. Peak discharge and time to peak have a practical truncations of the distribution tail at 0.5 h−1and 10 h, respectively. The quartile classification of the basins shows that some variables have distinct clusters, while others show almost no clustering at all. The study provides assessment of the potential flood risk and the potential recharge basins in the study area.

Flash flood potential prioritization of sub-basins in an ungauged basin in Turkey using traditional multi-criteria decision-making methods

Morphometric analysis of watersheds based on morphometric parameters is the most widely accepted method for watershed prioritization. However, traditional methods adopted for prioritization of sub-basins lack a standard classification of the morphometric parameters and ranges of their values. So, in this study several multi-criteria decision-making (MCDM) methods and a number of traditional methods are used for watershed prioritization regarding the flash flood potential of the sub-basins. Akcay, a small ungauged basin in Turkey, was chosen as the study area, and 12 morphometric parameters were determined for the basin. The geomorphological instantaneous unit hydrograph concept coupled with Monte Carlo analysis was used to estimate the flood yield of the basin due to the lack of flow data. Kendall tau and Spearman correlation coefficient tests and receiver operating characteristics analysis were performed to validate the results of the traditional methods and the MCDM approaches for prioritization of the sub-basins. Results showed that the AHP method could well predict the sub-basins with higher flood potential, while the methodology adopted in the study to determine the criteria weights obtained from ANP method in MCDM improved the prediction capability of those approaches, especially VIKOR. The initial values of criteria weights were determined to be effective on the predictions and sensitivity analysis. When the results of traditional methods and MCDM approaches were compared, the MCDM approaches were found to give improved results. This study showed that MCDM approaches can be used to provide an efficient management of basins regarding conservation of water resources and soil.

The Study of the Effect of Some Used Parameters on Geomorphologic Instantaneous Unit Hydrograph

The Study of the Effect of Some Used Parameters on Geomorphologic Instantaneous Unit Hydrograph

New method to calculate the dynamic factor\u2013flow velocity in Geomorphologic instantaneous unit hydrograph

The determination of characteristic flow velocity is a hydrodynamic problem needs to be solved in the application of geomorphologic instantaneous unit hydrograph (GIUH) for runoff simulation in areas with no or limited data. In this study, 120 watersheds are collected to construct a regression model; 85 of these basins are used for regression analysis, and the 35 remaining basins are utilized to verify the feasibility of the constructed model. Random forest algorithm is applied to screen out important geomorphologic factors from the 16 extracted factors that may affect flow velocity. Multivariate regression is used to establish the numerical relationship between velocity and the selected factors. Sensitivity analysis of each adopted factor in the constructed model is conducted using the LH-OAT method. The rationality and feasibility of the regression model are validated by comparing the flow velocity calculation with a previous approach, which is also calculated based on geomorphological parameters. Subsequently, the runoff simulation based on the GIUH model is evaluated using the proposed technique. Results demonstrate that the proposed formula possesses high fitting accuracy and can be easily used to calculate flow velocity and generate GIUH.

Physiographic Analysis of Tehri Dam Catchment and Development of GIUH Based Nash Model for Ungauged Rivers

Advanced information about incoming flows is required for operation of a variety of hydraulic structures including multipurpose storage hydropower projects. Inflow forecasts are used for optimum power generation during non -monsoon season and operation of gates and spillways during the flood season. In order to develop an inflow forecasting system for a reservoir, it has been observed that many a times number of ungauged rivers directly falling into the reservoirs are not accounted for. Such is the case for the Tehri Reservoir, where 16 small rivers/tributaries which are directly contributing to Tehri reservoir are ungauged. In the present study an attempt has been made to carry out physiographic objective Tehri catchment and to develop Geomorphological Instantaneous Unit Hydrograph (GIUH) for ungauged rivers/tributaries directly falling into the reservoir. GIUH developed for the ungauged rivers can be used to simulate the runoff from all the 16 ungauged rivers. Combining these GIUH models with a hydrological model of the other gauged rivers of the Tehri Catchment in the form of a network model provides a complete rainfall-runoff model. Thus, this study provides a useful input for the development of inflow forecasting model for the Tehri Dam as the network model can be used as flood forecasting model.

Integrating XAJ Model with GIUH Based on Nash Model for Rainfall-Runoff Modelling

The geomorphologic instantaneous unit hydrograph (GIUH) is an applicable approach that simulates the runoff for the ungauged basins. The nash model is an efficient tool to derive the unit hydrograph (UH), which only requires two items, including the indices n and k. Theoretically, the GIUH method describes the process of a droplet flowing from which it falls on to the basin outlet, only covering the flow concentration process. The traditional technique for flood estimation using GIUH method always uses the effective rainfall, which is empirically obtained and scant of accuracy, and then calculates the convolution of the effective rainfall and GIUH. To improve the predictive capability of the GIUH model, the Xin’anjiang (XAJ) model, which is a conceptual model with clear physical meaning, is applied to simulate the runoff yielding and the slope flow concentration, integrating with the GIUH derived based on Nash model to compute the river network flow convergence, forming a modified GIUH model for flood simulation. The average flow velocity is the key to obtain the indices k, and two methods to calculate the flow velocity were compared in this study. 10 flood events in three catchments in Fujian, China are selected to calibrate the model, and six for validation. Four criteria, including the time-to-peak error, the relative peak flow error, the relative runoff depth error, and the Nash–Sutcliff efficiency coefficient are computed for the model performance evaluation. The observed runoff value and simulated series in validation stage is also presented in the scatter plots to analyze the fitting degree. The analysis results show the modified model with a convenient calculation and a high fitting and illustrates that the model is reliable for the flood estimation and has potential for practical flood forecasting.