scholarly journals Proposed Swedish Spillway Design Guidelines Compared with Historical Flood Marks at Lake Siljan

1989 ◽  
Vol 20 (4-5) ◽  
pp. 293-304 ◽  
Author(s):  
Joakim Harlin
Keyword(s):  
Sensitivity Analysis ◽  
Water Level ◽  
Frequency Analysis ◽  
Return Period ◽  
Design Guidelines ◽  
Water Levels ◽  
Spring Flood ◽  
Design Flood ◽  
Design Floods ◽  
Modelling Assumptions

A comparison between the proposed Swedish spillway design floods and historic flood marks made at lake Siljan in central Sweden, is shown. Frequency analysis is performed incorporating pregauge information on water levels together with a sensitivity analysis of modelling assumptions. A water level of 0.42 to 0.75 metres above the highest historic flood mark (166.10 m.a.sl., 1659) was obtained when routing the design spring flood through lake Siljan. The design autumn flood lifted the lake to 1.56 to 1.52 metres below the highest flood mark. Return period for the design spring and autumn flood was estimated to about 1,000 years. The uncertainty in frequency analysis proved to have larger impact than modelling assumptions on estimating the risk of the design flood.

scholarly journals Design Flood Estimation: Exploring the Potentials and Limitations of Two Alternative Approaches

Water ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 729
Author(s):  
Kenechukwu Okoli ◽  
Korbinian Breinl ◽  
Maurizio Mazzoleni ◽  
Giuliano Di Baldassarre
Keyword(s):  
Frequency Analysis ◽  
Return Period ◽  
Peak Flow ◽  
Water Levels ◽  
Annual Maximum ◽  
Design Flood ◽  
River Flows ◽  
Alternative Approach ◽  
Maximum Water ◽  
Maximum Flows

The design of flood defence structures requires the estimation of flood water levels corresponding to a given probability of exceedance, or return period. In river flood management, this estimation is often done by statistically analysing the frequency of flood discharge peaks. This typically requires three main steps. First, direct measurements of annual maximum water levels at a river cross-section are converted into annual maximum flows by using a rating curve. Second, a probability distribution function is fitted to these annual maximum flows to derive the design peak flow corresponding to a given return period. Third, the design peak flow is used as input to a hydraulic model to derive the corresponding design flood level. Each of these three steps is associated with significant uncertainty that affects the accuracy of estimated design flood levels. Here, we propose a simulation framework to compare this common approach (based on the frequency analysis of annual maximum flows) with an alternative approach based on the frequency analysis of annual maximum water levels. The rationale behind this study is that high water levels are directly measured, and they often come along with less uncertainty than river flows. While this alternative approach is common for storm surge and coastal flooding, the potential of this approach in the context of river flooding has not been sufficiently explored. Our framework is based on the generation of synthetic data to perform a numerical experiment and compare the accuracy and precision of estimated design flood levels based on either annual maximum river flows (common approach) or annual maximum water levels (alternative approach).

scholarly journals Estimation of Design Flood for Rivers of Saurashtra Region Contributing into the Gulf of Khambhat

2016 ◽  
Vol 11 (3) ◽  
pp. 869-882
Author(s):  
Priyanka Kumari ◽  
Sushil Kumar
Keyword(s):  
Frequency Analysis ◽  
Return Period ◽  
Statistical Approach ◽  
River Basins ◽  
Hydraulic Structures ◽  
Deterministic Approach ◽  
Design Flood ◽  
Rainfall Frequency ◽  
Rainfall Frequency Analysis ◽  
Design Floods

Design flood has been estimated for rivers of Saurashtra region contributing into the Gulf of Khambhat using deterministic as well as statistical approach for planning, design and management of hydraulic structures. By comparing the results obtained by these approaches, one can easily estimate the flow rate or peak discharge to a given design return period and can establish the suitability of approach for this study area. Nine river basins with 20 dams of Saurashtra region were analyzed in this study. Though Saurashtra is one of the most water scarce regions of India yet it suffers from the flooding problem, as the numbers of rainy days are very less and the rainfall intensity is very high. Due to being a regulated basin, dam wise study was preferred. Deterministic approach was carried out using synthetic unit hydrograph (SUH) and regional flood formulae (RFF) methods for subzone-3a provided in Central Water Commission (CWC) report, 2001. Statistical approach was carried out using Rainfall frequency analysis employingGumbel’s EV1distribution. As there is no spill by these hydraulic structures and the annual flood data for the nine river sites are heavily affected by the storage dams in the upstream. Hence these data violate the basic principle of virgin flow. Hence the analysis of these data was not attempted further. The main objective of study was to carry out the rainfall frequency analysis for these river basins to get 24 hour rainfall for a return period of 25, 50 and 100 years for an individual basin instead of using the value obtained by iso-pluvial map to estimate the design flood. The overall results reveals that due to construction of number of dams in 9 river basins, design flood estimation on each dam by using deterministic approach is more feasible.Revised design floods using SUH and RFF method on the basis of estimated rainfall indicates over-estimated and under-estimated design floods. Since the percentage difference is very less between revised SUH and revised RFF method. So, for safety purpose one with higher value should be used.

Uncertainty in coastal flooding: modelling and visualisation

2020 ◽  
Author(s):  
John Maskell
Keyword(s):  
Water Level ◽  
Storm Surge ◽  
Return Period ◽  
Flood Risk ◽  
High Water ◽  
Coastal Flooding ◽  
Water Levels ◽  
Tidal Range ◽  
The Uk ◽  
Flood Maps

<p>Two case studies are considered in the UK, where uncertainty and drivers of coastal flood risk are explored through modelling and visualisations. Visualising the impact of uncertainty is a useful way of explaining the potential range of predicted or simulated flood risk to both expert and non-expert stakeholders.</p><p>Significant flooding occurred in December 2013 and January 2017 at Hornsea on the UK East Coast, where storm surge levels and waves overtopped the town’s coastal defences. Uncertainty in the potential coastal flooding is visualised at Hornsea due to the range of uncertainty in the 100-year return period water level and in the calculated overtopping due to 3 m waves at the defences. The range of uncertainty in the simulated flooding is visualised through flood maps, where various combinations of the uncertainties decrease or increase the simulated inundated area by 58% and 82% respectively.</p><p>Located at the mouth of the Mersey Estuary and facing the Irish Sea, New Brighton is affected by a large tidal range with potential storm surge and large waves. Uncertainty in the coastal flooding at the 100-year return period due to the combination of water levels and waves is explored through Monte-Carlo analysis and hydrodynamic modelling. Visualisation through flood maps shows that the inundation extent at New Brighton varies significantly for combined wave and surge events with a joint probability of 100 years, where the total flooded area ranges from 0 m<sup>2</sup> to 10,300 m<sup>2</sup>. Waves are an important flood mechanism at New Brighton but are dependent on high water levels to impact the coastal defences and reduce the effective freeboard. The combination of waves and high-water levels at this return level not only determine the magnitude of the flood extent but also the spatial characteristics of the risk, whereby flooding of residential properties is dominated by overflow from high water levels, and commercial and leisure properties are affected by large waves that occur when the water level is relatively high at the defences.</p>

scholarly journals ANALISIS BANJIR DAN TINGGI MUKA AIR PADA RUAS SUNGAI CILIWUNG STA 7+646 s/d STA 15+049

2018 ◽  
Vol 7 (1) ◽  
pp. 43-49
Author(s):  
Redaksi Tim Jurnal
Keyword(s):  
Frequency Analysis ◽  
Return Period ◽  
Synthetic Data ◽  
Gumbel Distribution ◽  
Peak Discharge ◽  
Design Flood ◽  
Distribution Method ◽  
Flood Peak ◽  
Method Of Calculation ◽  
Flood Discharge

The problem of flooding in DKI Jakarta is considered normal because almost every year can hit the city of Jakarta especially during the rainy season. In DKI Jakarta itself there are several rivers, one of which is Ciliwung River which is the most influential river in DKI Jakarta which often cause flood every year. The purpose of this research is to know the location of flood / river flood that occurs in the segments along Ciliwung River STA 7 + 646 s / d STA 15 + 049. Data processing begins with the calculation of average rainfall, frequency analysis, and then hour-time rain distribution. Method of calculation of flood discharge using the synthetic unit of Nakayasu and Gama I synthetic data. Rainfall data using 2 observation stations for 3 years rain (2014-2016). In the frequency analysis used Gumbel distribution berdasrkan test results suitability data Smirnov- Kolmogorov and Chi-Square. The result of flood peak discharge design with HSS Nakayasu on return period Q5 = 687,80 m3 / dt, Q10 = 743,21 m3 / dt, Q20 = 796,36 m3 / s, Q50 = 865,15 m3 / dt, Q100 = 916,71 m3 / s, while flood peak discharge design with HSS Gama I on return period Q5 = 347,03 m3 / s, Q10 = 372,12 m3 / s, Q20 = 396,20 m3 / s, Q50 = 427, 36 m3 / s, Q100 = 450,71 m3 / s. The design flood discharge value approaching the measured debit value is HSS Nakayasu. Steps continued using HEC-RAS 4.1.0 software to determine the capacity of river catchment by using Nakayasu discharge. After analyzing using the software, most stationing of the Ciliwung River at STA 7 + 646 to STA 15 + 049 can not accommodate the planned discharge during the 20th anniversary period, hence the need for river improvements in the form of river normalization and elevation of dikes.

scholarly journals EXTREME WATER LEVEL EXCEEDANCE PROBABILITIES AROUND AUSTRALIA

2012 ◽  
Vol 1 (33) ◽  
pp. 53
Author(s):  
Leigh MacPherson ◽  
Ivan David Haigh ◽  
Matthew Mason ◽  
Sarath Wijeratne ◽  
Charitha Pattiaratchi ◽  
...  
Keyword(s):  
Tropical Cyclone ◽  
Water Level ◽  
Return Period ◽  
Meteorological Data ◽  
Storm Surges ◽  
Value Theory ◽  
Water Levels ◽  
Sea Levels ◽  
Extreme Water Level ◽  
Extreme Water Levels

The potential impacts of extreme water level events on our coasts are increasing as populations grow and sea levels rise. To better prepare for the future, coastal engineers and managers need accurate estimates of average exceedance probabilities for extreme water levels. In this paper, we estimate present day probabilities of extreme water levels around the entire coastline of Australia. Tides and storm surges generated by extra-tropical storms were included by creating a 61-year (1949-2009) hindcast of water levels using a high resolution depth averaged hydrodynamic model driven with meteorological data from a global reanalysis. Tropical cyclone-induced surges were included through numerical modelling of a database of synthetic tropical cyclones equivalent to 10,000 years of cyclone activity around Australia. Predicted water level data was analysed using extreme value theory to construct return period curves for both the water level hindcast and synthetic tropical cyclone modelling. These return period curves were then combined by taking the highest water level at each return period.

scholarly journals Flood frequency analysis of the Djetinja river

2010 ◽  
Vol 90 (2) ◽  
pp. 15-28 ◽  
Author(s):  
Dragana Milijasevic
Keyword(s):  
Water Resources ◽  
Water Level ◽  
Frequency Analysis ◽  
Drainage Basin ◽  
Flood Frequency ◽  
Water Levels ◽  
Flood Frequency Analysis ◽  
Extreme Water Levels ◽  
High Flows ◽  
Hydrological Forecast

Based on extreme water levels data, using the method of series, a forecast for protection of river has been accomplished, i.e. probable water level maximums of the Djetinja river at Sengolj were measured. High flows were analyzed with a probability from 0.01% to 99.9%. These probabilities indicate the occurrence of high flows of certain values once in 10.000, 1.000, 100, 33, 20 etc years. Applying a hydrological forecast, one can perceive the possibility for using water resources for various purposes, as well as protection of areas and people from flooding. A review of the greatest floods in the Djetinja drainage basin in the last hundred years is given in this paper. .

scholarly journals Analisis Debit Banjir Rancangan Sub DAS Air Bengkulu Menggunakan Analisis Frekuensi dan Metode Distribusi

2020 ◽  
Vol 17 (1) ◽  
pp. 1-9
Author(s):  
Gusta Gunawan Gunawan ◽  
Besperi Besperi ◽  
Liza Purnama
Keyword(s):  
Frequency Analysis ◽  
Return Period ◽  
Estimation Method ◽  
Type I ◽  
Distribution Analysis ◽  
Design Flood ◽  
Chi Square ◽  
Distribution Method ◽  
Average Value ◽  
Design Discharge

Abstract The Design discharge is the important data needed for design of the water infrastructure. The purpose of this study is to estimate the design discharge with a variety of times using a frequency analysis in the Air Bengkulu Sub-watershed. Rain fall data were obtained from the BMKG of Bengkulu province, its starting from 2009 to 2018 years. The design flood estimation method used a statistical method. It is using the distribution method. The initial stage of the research is to process rain data and then conduct frequency analysis. The mathematical equation for frequency analysis includes statistical equations to determine the average value, standard deviation, coefficient of variation, skewness coefficient and kurtosis coefficient. The method used in determining the type of distribution for frequency analysis in this study uses the Gumbel Type I distribution method, Pearson Log Type III, Normal, and Normal Log. Distribution fit test was performed with chi square test and Kalmogorof Smirnov test. The results of estimated design discharges for the 2 years return period, 5 years return period, 10 years return period, 25 years return period, 50 years return period and 100 years returns period in the Air Bengkulu down stream Sub-watershed are respectively 125.16 m3 / sec (2 years return period), 145.24 m3 / sec (5 years return period), 157.59 m3 / sec (10 years return period), 172.43 m3 / sec (25 years return period), 183.03 m3 / sec (50 years return period) and 193.34 m3 / sec (100 years return period).   Keywords: watershed, Air Bengkulu, Design Discharge, Frequency Analysis, Distribution Analysis

Study on the Extreme High Water Levels and Wave Heights of Different Return Periods in Laizhou Bay, China

2017 ◽  
Author(s):  
Chunyan Zhou ◽  
Jinhai Zheng ◽  
Jisheng Zhang ◽  
Xiaoying Fu
Keyword(s):  
Water Level ◽  
Wave Height ◽  
Return Period ◽  
Current Velocity ◽  
Yellow River ◽  
River Mouth ◽  
High Water ◽  
Water Levels ◽  
Laizhou Bay ◽  
Distribution Method

Based on good simulation results during storm events in 2009, MIKE21 was used to study the extreme water level, current velocity and wave height in Laizhou Bay, China. 95 extreme weather processes during 1988–2012 were simulated. For each event, coupled hydrodynamic and wave modules of MIKE21 was chosen to calculate the maximum water level and current velocity. The Gumbel distribution method, commonly used for estimating return-period values of marine hydrodynamic variables, is adopted in this study. The extreme high water level of 50-year return period in Laizhou Bay can reach 2.6–3.8 m; and that of 100-year return period can be as high as 2.8–4.6 m. The 50-year and 100-year return-period values of current velocity can reach up to about 2.8 m/s and 3.2 m/s respectively, both around the Yellow River mouth. Wave height strongly depends on water depth, water level rise, wind speed and direction. The results provide parameter reference for structure design in the Laizhou Bay.

scholarly journals Assessing the performance of regional flood frequency analysis methods in South Africa

Water SA ◽  
2018 ◽  
Vol 44 (3 July) ◽  
Author(s):  
JJ Nathanael ◽  
JC Smithers ◽  
MJC Horan
Keyword(s):  
South Africa ◽  
Frequency Analysis ◽  
Relevant Literature ◽  
Flood Frequency ◽  
Flood Frequency Analysis ◽  
Design Flood ◽  
Regional Flood Frequency Analysis ◽  
Design Floods ◽  
Regional Flood Frequency ◽  
Better Than

In engineering and flood hydrology, the estimation of a design flood associates the magnitude of a flood with a level of exceedance, or return period, for a given site. The use of a regional flood frequency analysis (RFFA) approach improves the accuracy and reliability of estimates of design floods. However, no RFFA method is currently widely used in South Africa, despite a number of RFFA studies having been undertaken in Africa and which include South Africa in their study areas. Hence, the performance of the current RFFA approaches needs to be assessed in order to determine the best approaches to use and to determine if a new RFFA approach needs to be developed for use in South Africa. Through a review of the relevant literature it was found that the Meigh et al. (1997) method, the Mkhandi et al. (2000) method, the Görgens (2007) Joint Peak-Volume (JPV) method and the Haile (2011) method are available for application in a nationwide study. The results of the study show that the Haile method generally performs better than the other RFFA methods; however, it also consistently underestimates design floods. Due to the poor overall performance of the RFFA methods assessed, it is recommended that a new RFFA method be developed for application in design flood practice in South Africa.

scholarly journals Integrating Monte Carlo and the Hydrodynamic Model for Predicting Extreme Water Levels in River Systems

2018 ◽  
Author(s):  
Wen-Cheng Liu ◽  
Hong-Ming Liu
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Water Level ◽  
Engineering Design ◽  
Frequency Analysis ◽  
Hydrodynamic Model ◽  
Water Levels ◽  
Return Periods ◽  
River Systems ◽  
Extreme Water Levels

Estimates of extreme water level return periods in river systems are crucial for hydraulic engineering design and planning. Recorded historical water level data of Taiwan’s rivers are not long enough for traditional frequency analyses when predicting extreme water levels for different return periods. In this study, the integration of a one-dimensional flash flood routing hydrodynamic model with the Monte Carlo simulation was developed to predict extreme water levels in the Danshuei River system of northern Taiwan. The numerical model was calibrated and verified with observed water levels using four typhoon events. The results indicated a reasonable agreement between the model simulation and observation data. Seven parameters, including the astronomical tide and surge height at the mouth of the Danshuei River and the river discharge at five gauge stations, were adopted to calculate the joint probability and generate stochastic scenarios via the Monte Carlo simulation. The validated hydrodynamic model driven by the stochastic scenarios was then used to simulate extreme water levels for further frequency analysis. The design water level was estimated using different probability distributions in the frequency analysis at five stations. The design high-water levels for a 200-year return period at Guandu Bridge, Taipei Bridge, Hsin-Hai Bridge, Da-Zhi Bridge, and Chung-Cheng Bridge were 2.90 m, 5.13 m, 6.38 m, 6.05 m, and 9.94 m, respectively. The estimated design water levels plus the freeboard are proposed and recommended for further engineering design and planning.

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