Design flood estimates in mountain streams – the need for a geomorphic approach

2001 ◽  
Vol 28 (3) ◽  
pp. 425-439 ◽  
Author(s):  
Matthias Jakob ◽  
Peter Jordan
Keyword(s):  
Debris Flows ◽  
Regional Analysis ◽  
Landslide Dam ◽  
Flood Frequency ◽  
Flood Hazards ◽  
Design Flood ◽  
Rainfall Frequency ◽  
Outburst Floods ◽  
Streamflow Data ◽  
Geomorphic Processes

Estimates of design flood frequencies are routinely required for engineering purposes on ungauged streams and streams with a limited period of streamflow record. In these cases, the design flood is determined either by rainfall frequency–duration analysis, regional analysis of streamflow data, or by extrapolation of a short record from a gauged stream. Although these types of analyses are valuable in a first approximation of peak discharges for different return periods, there is increasing evidence that geomorphic processes such as debris flows, landslide dam failures, glacial outburst floods, and even snow avalanches in the watershed can significantly exceed these estimates. This paper highlights the problem of a purely hydrologic approach for design flood estimates using several case studies, and suggests procedures to routinely include geomorphic processes in standard flood frequency studies.Key words: debris flows, debris floods, landslide dams, flood hazards, outburst floods, frequency analysis.

A Geomorphic Approach to the Design of Pipeline Crossings of Mountain Streams

2004 ◽  
Author(s):  
Matthias Jakob ◽  
Michael Porter ◽  
K. Wayne Savigny ◽  
Eugene Yaremko
Keyword(s):  
Return Period ◽  
Debris Flows ◽  
Peak Discharge ◽  
Hydrological Processes ◽  
Mountain Streams ◽  
Design Flood ◽  
Fluvial Process ◽  
Flood Discharge ◽  
Outburst Floods ◽  
Pipeline Crossing

Several hydrological methods are available to determine flood discharge and scour of streams at pipeline crossings. These methods are appropriate for streams dominated by purely hydrological processes, but fail where other, more hazardous processes occur within the design recurrence interval. Several investigations have shown that scour, impact and aggradation associated with debris flows, outburst floods or related phenomena may fundamentally change the parameters needed for proper pipeline crossing design. Depending on the process type, the peak discharge of the hazardous process can exceed that of the design flood (typically 50 to 200 year return period) by a factor of 2 to 50. Similarly, scour or aggradation by a non-fluvial process can exceed the hydrologically-derived estimates by several factors. It is therefore recommended that a geomorphic approach be taken in recognizing and quantifying the potential for non-fluvial processes and that the findings be integrated in the design of pipeline crossings.

scholarly journals Geomorphic effects of recurrent outburst superfloods in the Yigong River on the southeastern margin of Tibet

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Kaiheng Hu ◽  
Chaohua Wu ◽  
Li Wei ◽  
Xiaopeng Zhang ◽  
Qiyuan Zhang ◽  
...  
Keyword(s):  
Landslide Dam ◽  
Upstream Migration ◽  
One Dimensional ◽  
Landform Evolution ◽  
Outburst Floods ◽  
Stepwise Method ◽  
Large Landslide ◽  
Southeastern Margin ◽  
Channel Slope ◽  
The One

AbstractLandslide dam outburst floods have a significant impact on landform evolution in high mountainous areas. Historic landslide dams on the Yigong River, southeastern Tibet, generated two outburst superfloods > 105 m3/s in 1902 and 2000 AD. One of the slackwater deposits, which was newly found immediately downstream of the historic dams, has been dated to 7 ka BP. The one-dimensional backwater stepwise method gives an estimate of 225,000 m3/s for the peak flow related to the paleo-stage indicator of 7 ka BP. The recurrence of at least three large landslide dam impoundments and super-outburst floods at the exit of Yigong Lake during the Holocene greatly changed the morphology of the Yigong River. More than 0.26 billion m3 of sediment has been aggraded in the dammed lake while the landslide sediment doubles the channel slope behind the dam. Repeated landslide damming may be a persistent source of outburst floods and impede the upstream migration of river knickpoints in the southeastern margin of Tibet.

Debris Flows Resulting From Glacial-Lake Outburst Floods in Tibet, China

2010 ◽  
Vol 31 (6) ◽  
pp. 508-527 ◽  
Author(s):  
Peng Cui ◽  
Chao Dang ◽  
Zunlan Cheng ◽  
Kevin M. Scott
Keyword(s):  
Debris Flows ◽  
Glacial Lake ◽  
Outburst Floods ◽  
Glacial Lake Outburst Floods

Comparison of Annual Maximum and Peaks Over Threshold Methods with Automated Threshold Selection in Flood Frequency Analysis: A Case Study for Australia

2021 ◽  
Author(s):  
Xiao Pan ◽  
Ataur Rahman
Keyword(s):  
Frequency Analysis ◽  
Flood Frequency ◽  
Distribution Functions ◽  
Flood Frequency Analysis ◽  
Annual Maximum ◽  
Threshold Selection ◽  
Peaks Over Threshold ◽  
Design Flood ◽  
Threshold Detection ◽  
Using Data

Abstract Flood frequency analysis (FFA) enables fitting of distribution functions to observed flow data for estimation of flood quantiles. Two main approaches, Annual Maximum (AM) and peaks-over-threshold (POT) are adopted for FFA. POT approach is under-employed due to its complexity and uncertainty associated with the threshold selection and independence criteria for selecting peak flows. This study evaluates the POT and AM approaches using data from 188 gauged stations in south-east Australia. POT approach adopted in this study applies a different average numbers of events per year fitted with Generalised Pareto (GP) distribution with an automated threshold detection method. The POT model extends its parametric approach to Maximum Likelihood Estimator (MLE) and Point Moment Weighted Unbiased (PMWU) method. Generalised Extreme Value (GEV) distribution using L-moment estimator is used for AM approach. It has been found that there is a large difference in design flood estimates between the AM and POT approaches for smaller average recurrence intervals (ARI), with a median difference of 25% for 1.01 year ARI and 5% for 50 and 100 years ARIs.

scholarly journals Regional analysis using the Geomorphologic Instantaneous Unit Hydrograph (GIUH) method

2014 ◽  
Vol 9 (No. 1) ◽  
pp. 25-30 ◽  
Author(s):  
M.R. Khaleghi ◽  
J. Ghodusi ◽  
H. Ahmadi
Keyword(s):  
High Efficiency ◽  
Linear Regression Analysis ◽  
Regional Analysis ◽  
Suitable Model ◽  
Rainfall Runoff ◽  
Unit Hydrograph ◽  
Design Flood ◽  
Ungauged Catchments ◽  
Northern Iran ◽  
Simulation Accuracy

The construction of design flood hydrographs for ungauged drainage areas has traditionally been approached by regionalization, i.e. the transfer of information from the gauged to the ungauged catchments in a region. Such approaches invariably depend upon the use of multiple linear regression analysis to relate unit hydrograph parameters to catchment characteristics and generalized rainfall statistics. In the present study, Geomorphologic Instaneous Unit Hydrograph (GIUH) was applied to simulate the rainfall-runoff process and also to determine the shape and dimensions of outlet runoff hydrographs in a 37.1 km<sup>2</sup> area in the Ammameh catchment, located at northern Iran. The first twenty-one equivalent rainfall-runoff events were selected, and a hydrograph of outlet runoff was calculated for each event. An intercomparison was made for the three applied approaches in order to propose a suitable model approach that is the overall objective of this study. Hence, the time to peak and peak flow of outlet runoff in the models were then compared, and the model that most efficiently estimated hydrograph of outlet flow for similar regions was determined. Statistical analyses of the models demonstrated that the GIUH model had the smallest main relative and square error. The results obtained from the study confirmed the high efficiency of the GIUH and its ability to increase simulation accuracy for runoff and hydrographs. The modified GIUH approach as described is therefore recommended for further investigation and intercomparison with regression-based regionalization methods.

scholarly journals Non-Stationary Flood Frequency Analysis Using Cubic B-Spline-Based GAMLSS Model

Water ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1867
Author(s):  
Chunlai Qu ◽  
Jing Li ◽  
Lei Yan ◽  
Pengtao Yan ◽  
Fang Cheng ◽  
...  
Keyword(s):  
Quantile Regression ◽  
Frequency Analysis ◽  
Flood Frequency ◽  
Flood Frequency Analysis ◽  
Design Flood ◽  
Statistical Parameters ◽  
B Spline ◽  
Quantile Regression Model ◽  
Design Values ◽  
The Relationship

Under changing environments, the most widely used non-stationary flood frequency analysis (NFFA) method is the generalized additive models for location, scale and shape (GAMLSS) model. However, the model structure of the GAMLSS model is relatively complex due to the large number of statistical parameters, and the relationship between statistical parameters and covariates is assumed to be unchanged in future, which may be unreasonable. In recent years, nonparametric methods have received increasing attention in the field of NFFA. Among them, the linear quantile regression (QR-L) model and the non-linear quantile regression model of cubic B-spline (QR-CB) have been introduced into NFFA studies because they do not need to determine statistical parameters and consider the relationship between statistical parameters and covariates. However, these two quantile regression models have difficulties in estimating non-stationary design flood, since the trend of the established model must be extrapolated infinitely to estimate design flood. Besides, the number of available observations becomes scarcer when estimating design values corresponding to higher return periods, leading to unreasonable and inaccurate design values. In this study, we attempt to propose a cubic B-spline-based GAMLSS model (GAMLSS-CB) for NFFA. In the GAMLSS-CB model, the relationship between statistical parameters and covariates is fitted by the cubic B-spline under the GAMLSS model framework. We also compare the performance of different non-stationary models, namely the QR-L, QR-CB, and GAMLSS-CB models. Finally, based on the optimal non-stationary model, the non-stationary design flood values are estimated using the average design life level method (ADLL). The annual maximum flood series of four stations in the Weihe River basin and the Pearl River basin are taken as examples. The results show that the GAMLSS-CB model displays the best model performance compared with the QR-L and QR-CB models. Moreover, it is feasible to estimate design flood values based on the GAMLSS-CB model using the ADLL method, while the estimation of design flood based on the quantile regression model requires further studies.

scholarly journals Deriving Design Flood Hydrograph Based on Conditional Distribution: A Case Study of Danjiangkou Reservoir in Hanjiang Basin

2016 ◽  
Vol 2016 ◽  
pp. 1-16 ◽  
Author(s):  
Changjiang Xu ◽  
Jiabo Yin ◽  
Shenglian Guo ◽  
Zhangjun Liu ◽  
Xingjun Hong
Keyword(s):  
Joint Probability ◽  
Flood Frequency ◽  
Peak Discharge ◽  
Flood Frequency Analysis ◽  
Design Flood ◽  
Copula Functions ◽  
Danjiangkou Reservoir ◽  
Flood Peak ◽  
Flood Hydrograph

Design flood hydrograph (DFH) for a dam is the flood of suitable probability and magnitude adopted to ensure safety of the dam in accordance with appropriate design standards. Estimated quantiles of peak discharge and flood volumes are necessary for deriving the DFH, which are mutually correlated and need to be described by multivariate analysis methods. The joint probability distributions of peak discharge and flood volumes were established using copula functions. Then the general formulae of conditional most likely composition (CMLC) and conditional expectation composition (CEC) methods that consider the inherent relationship between flood peak and volumes were derived for estimating DFH. The Danjiangkou reservoir in Hanjiang basin was selected as a case study. The design values of flood volumes and 90% confidence intervals with different peak discharges were estimated by the proposed methods. The performance of CMLC and CEC methods was also compared with conventional flood frequency analysis, and the results show that CMLC method performs best for both bivariate and trivariate distributions which has the smallest relative error and root mean square error. The proposed CMLC method has strong statistical basis with unique design flood composition scheme and provides an alternative way for deriving DFH.

scholarly journals Dimensionless Assessment Method of Landslide Dam Formation Caused by Tributary Debris Flow Events

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Kun-Ting Chen ◽  
Xiao-Qing Chen ◽  
Gui-Sheng Hu ◽  
Yu-Shu Kuo ◽  
Yan-Rong Huang ◽  
...  
Keyword(s):  
Debris Flow ◽  
Water Depth ◽  
Debris Flows ◽  
Landslide Dam ◽  
Assessment Method ◽  
Main Stream ◽  
Deposition Thickness ◽  
The Relationship ◽  
Prepared Response

In this study, we develop a dimensionless assessment method to evaluate landslide dam formation by considering the relationship between the run-out distance of a tributary debris flow and the width of the main stream, deposition thickness of the tributary debris flow, and the water depth of the main stream. Based on the theory of debris flow run-out distance and fan formation, landslide dam formation may result from a tributary debris flow as a result of two concurrent formation processes: (1) the run-out distance of the tributary debris flow must be greater than the width of the main stream, and (2) the minimum deposition thickness of the tributary debris flow must be higher than the in situ water depth of the main stream. At the confluence, one of four types of depositional scenarios may result: (1) the tributary debris flow enters into the main stream and forms a landslide dam; (2) the tributary debris flow enters into the main stream but overflow occurs, thus preventing complete blockage of the main stream; (3) the tributary debris flow enters into the main stream, does not reach the far bank, and sediment remains partially above the water elevation of the main stream; or (4) the tributary debris flow enters into the main stream, does not reach the far bank, and sediment is fully submerged in the main stream. This method was applied to the analysis of 11 tributary debris flow events during Typhoon Morakot, and the results indicate that the dimensionless assessment method can be used to estimate potential areas of landslide dam formation caused by tributary debris flows. Based on this method, government authorities can determine potential areas of landslide dam formation caused by debris flows and mitigate possible disasters accordingly through a properly prepared response plan, especially for early identification.

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