Application of a rainfall-runoff model for regional-scale flood inundation mapping for the Langat River Basin

2016 ◽  
Vol 11 (2) ◽  
pp. 373-383
Author(s):  
Majid Mirzaei ◽  
Mina Faghih ◽  
Tan Pei Ying ◽  
Ahmed El-Shafie ◽  
Yuk Feng Huang ◽  
...  
Keyword(s):  
Assessment Tool ◽  
Regional Scale ◽  
Extreme Rainfall ◽  
Water Levels ◽  
Army Corps ◽  
Return Periods ◽  
Flow Rates ◽  
Peak Flows ◽  
Langat River ◽  
Maximum Flows

Rapid growth in recent decades has changed engineering concepts about the approach to controlling storm water in cities. Over the past years flood events have occurred more frequently in several countries in the tropics. In this study the behavior of Langat River in Malaysia was analyzed using the hydrodynamic modeling software (HEC-RAS) developed by the ‘Hydrologic Engineering Center, U.S. Army Corps of Engineers’, to simulate different water levels and flow rates corresponding to different return periods from the available database. The aim was to forecast peak flows, based on rainfall data and the maximum rate of precipitation in different return periods in storms of different duration. The maximum flows were obtained from the Automated Geospatial Watershed Assessment tool for the different return periods, and the peak flows from extreme rainfall were applied to HEC-RAS to simulate different water levels and flow rates corresponding to different return periods. The water level along the river and its tributaries could then be analyzed for different flow conditions.

scholarly journals BARRIER ISLAND RESTORATION FOR STORM DAMAGE REDUCTION: WILLAPA BAY, WASHINGTON, USA

2011 ◽  
Vol 1 (32) ◽  
pp. 32
Author(s):  
David R Michalsen ◽  
Steven D Babcock ◽  
Lihwa Lin
Keyword(s):  
Assessment Tool ◽  
Barrier Island ◽  
Water Levels ◽  
Storm Event ◽  
Army Corps ◽  
Storm Damage ◽  
Indian Reservation ◽  
Island Restoration ◽  
Damage Reduction ◽  
Extreme Water Levels

The U.S. Army Corps of Engineers, Seattle District has completed a feasibility study and determined barrier island restoration to be the most appropriate long-term coastal flood and storm damage reduction measure for the Shoalwater Indian Reservation. Over the last century, Cape Shoalwater has receded more than 2.8 miles. By 1990, the Shoalwater Reservation’s only remaining protection from storm wave attack was a series of barrier islands fronting Tokeland Peninsula. Extreme water levels coincident with strong winter storms have historically inundated this low lying topography and are responsible for the erosion and overwash of the protective barrier island known as Graveyard Spit. Here a simple risk assessment tool is presented for identifying flood risk to the Shoalwater Reservation infrastructure. Statistical analysis of extreme water levels and numerical modeling is utilized to determine the extent of inundation. From the analysis it was determined 54% of the inventoried infrastructure is at risk during a storm event equivalent to the observed event on March 3, 1999. With the barrier island restoration it was found that this risk is reduced to 7%.

scholarly journals Flood Inundation Assessment in the Low-Lying River Basin Considering Extreme Rainfall Impacts and Topographic Vulnerability

Water ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 896
Author(s):  
Thanh Thu Nguyen ◽  
Makoto Nakatsugawa ◽  
Tomohito J. Yamada ◽  
Tsuyoshi Hoshino
Keyword(s):  
River Basin ◽  
Extreme Rainfall ◽  
Flood Damage ◽  
Water Levels ◽  
Flood Inundation ◽  
Inundation Area ◽  
Inundation Depth ◽  
Study Results ◽  
Inundation Duration ◽  
Short Time

This study aims to evaluate the change in flood inundation in the Chitose River basin (CRB), a tributary of the Ishikari River, considering the extreme rainfall impacts and topographic vulnerability. The changing impacts were assessed using a large-ensemble rainfall dataset with a high resolution of 5 km (d4PDF) as input data for the rainfall–runoff–inundation (RRI) model. Additionally, the prediction of time differences between the peak discharge in the Chitose River and peak water levels at the confluence point intersecting the Ishikari River were improved compared to the previous study. Results indicate that due to climatic changes, extreme river floods are expected to increase by 21–24% in the Ishikari River basin (IRB), while flood inundation is expected to be severe and higher in the CRB, with increases of 24.5, 46.5, and 13.8% for the inundation area, inundation volume, and peak inundation depth, respectively. Flood inundation is likely to occur in the CRB downstream area with a frequency of 90–100%. Additionally, the inundation duration is expected to increase by 5–10 h here. Moreover, the short time difference (0–10 h) is predicted to increase significantly in the CRB. This study provides useful information for policymakers to mitigate flood damage in vulnerable areas.

scholarly journals A comparative survey of the impacts of extreme rainfall in two international case studies

2017 ◽  
Author(s):  
Matthieu Spekkers ◽  
Viktor Rözer ◽  
Annegret Thieken ◽  
Marie-Claire ten Veldhuis ◽  
Heidi Kreibich
Keyword(s):  
Case Studies ◽  
Online Survey ◽  
Residential Buildings ◽  
Age Groups ◽  
Extreme Rainfall ◽  
Water Levels ◽  
Economic Losses ◽  
Biased Sampling ◽  
Wide Range ◽  
Damage Data

Abstract. Flooding is assessed as the most important natural hazard in Europe, causing thousands of deaths, affecting millions of people and accounting for large economic losses in the past decade. Little is known about the damage processes associated with extreme rainfall in cities, due to a lack of accurate, comparable and consistent damage data. The objective of this study is to investigate the impacts of extreme rainfall on residential buildings and how affected households coped with these impacts in terms of precautionary and emergency actions. Analyses are based on a unique dataset of damage characteristics and a wide range of potential damage explaining variables at the household level, collected through computer-aided telephone interviews (CATI) and an online survey. Exploratory data analyses based on a total of 859 completed questionnaires in the cities of Münster (Germany) and Amsterdam (the Netherlands) revealed that the uptake of emergency measures is related to characteristics of the hazardous event. In case of high water levels, more efforts are made to reduce damage, while emergency response that aims to prevent damage is less likely to be effective. The difference in magnitude of the events in Münster and Amsterdam in terms of rainfall intensity and water depth, is probably also the most important cause for the differences between the cities in terms of the suffered financial losses. Factors that significantly contributed to damage in at least one of the case studies are water contamination, the presence of a basement in the building and people's awareness of the upcoming event. Moreover, this study confirms conclusions by previous studies that people's experience with damaging events positively correlates with precautionary behaviour. For improving future damage data acquisition, we recommend to include cell-phones in a CATI survey to avoid biased sampling towards certain age groups.

scholarly journals A synthetic view of rainfall intensification in the West African Sahel

2022 ◽  
Author(s):  
Guillaume Chagnaud ◽  
Geremy Panthou ◽  
Theo Vischel ◽  
Thierry Lebel
Keyword(s):  
Decadal Variability ◽  
Regional Scale ◽  
Daily Rainfall ◽  
Extreme Value Distribution ◽  
Extreme Rainfall ◽  
West African ◽  
Rainfall Regime ◽  
The West ◽  
West African Sahel ◽  
African Sahel

Abstract The West African Sahel has been facing for more than 30 years an increase in extreme rainfalls with strong socio-economic impacts. This situation challenges decision-makers to define adaptation strategies in a rapidly changing climate. The present study proposes (i) a quantitative characterization of the trends in extreme rainfalls at the regional scale, (ii) the translation of the trends into metrics that can be used by hydrological risk managers, (iii) elements for understanding the link between the climatology of extreme and mean rainfall. Based on a regional non-stationary statistical model applied to in-situ daily rainfall data over the period 1983-2015, we show that the region-wide increasing trend in extreme rainfalls is highly significant. The change in extreme value distribution reflects an increase in both the mean and variability, producing a 5%/decade increase in extreme rainfall intensity whatever the return period. The statistical framework provides operational elements for revising the design methods of hydraulic structures which most often assume a stationary climate. Finally, the study shows that the increase in extreme rainfall is more attributable to an increase in the intensity of storms (80%) than to their occurrence (20%), reflecting a major disruption from the decadal variability of the rainfall regime documented in the region since 1950.

Testing the impacts of wildfire on hydrological and sediment response using the OpenLISEM model

2021 ◽  
Author(s):  
Jinfeng Wu ◽  
João Pedro Nunes ◽  
Jantiene E. M. Baartman
Keyword(s):  
Water Discharge ◽  
Extreme Rainfall ◽  
Fire Occurrence ◽  
Return Periods ◽  
Extreme Rainfall Events ◽  
Rainfall Events ◽  
Erosion Risk ◽  
Sediment Yields ◽  
Splash Erosion ◽  
Event Based

<p>Wildfires have become a major concern to society in recent decades because increases in the number and severity of wildfires have negative effects on soil and water resources, especially in headwater areas. Models are typically applied to estimate the potential adverse effects of fire. However, few modeling studies have been conducted for meso-scale catchments, and only a fraction of these studies include transport and deposition of eroded material within the catchment or represent spatial erosion patterns. In this study, we firstly designed the procedure of event-based automatic calibration using PEST, parameters ensemble, and jack-knife cross-validation that is suitable for event-based OpenLISEM calibration and validation, especially in data-scarce burned areas. The calibrated and validated OpenLISEM proved capable of providing reasonable accurate predictions of hydrological responses and sediment yields in this burned catchment. Then the model was applied with design storms of six different return periods (0.2, 0.5, 1, 2, 5, and 10 years) to simulate and evaluate pre- and post-wildfire hydrological and erosion responses at the catchment scale. Our results show rainfall amount and intensity play a more important role than fire occurrence in the catchment water discharge and sediment yields, while fire occurrence is regarded as an important factor for peak water discharge, indicating that high post-fire hydro-sedimentary responses are frequently related to extreme rainfall events. The results also suggest a partial shift from flow to splash erosion after fire, especially for higher return periods, explained by a combination of higher splash erosion in burnt upstream areas with a limited sediment transport capacity of surface runoff, preventing flow erosion in downstream areas. In consequence, the pre-fire erosion risk in the croplands of this catchment is partly shifted to a post-fire erosion risk in upper slope forest and natural areas, especially for storms with lower return periods, although erosion risks in croplands are important both before and after fires. This is relevant, as a shift of sediment sources to burnt areas might lead to downstream contamination even if sediment yields remain small. These findings have significant implications to identify areas for post-wildfire stabilization and rehabilitation, which is particularly important given the predicted increase in the occurrence of fires and extreme rainfall events with climate change.</p>

scholarly journals Global flood hazard map and exposed GDP comparison: a China case study

2020 ◽  
Author(s):  
Jerom P. M. Aerts ◽  
Steffi Uhlemann-Elmer ◽  
Dirk Eilander ◽  
Philip J. Ward
Keyword(s):  
Return Period ◽  
Flood Hazard ◽  
Regional Scale ◽  
Flood Protection ◽  
Economic Losses ◽  
Return Periods ◽  
Hazard Maps ◽  
High Exposure ◽  
Pluvial Flooding

Abstract. Floods are among the most frequent and damaging natural hazard events in the world. In 2016, economic losses from flooding amounted to $56 bn globally, of which $20 bn occurred in China (Munich Re, 2017). National or regional scale mapping of flood hazard is at present providing an inconsistent and incomplete picture of floods. Over the past decade global flood hazard models have been developed and continuously improved. There is now a significant demand for testing of the global hazard maps generated by these models in order to understand their applicability for international risk reduction strategies and for reinsurance portfolio risk assessments using catastrophe models. We expand on existing methods for comparing global hazard maps and analyse 8 global flood models (GFMs) that represent the current state of the global flood modelling community. We apply our comparison to China as a case study and, for the first time, we include industry models, pluvial flooding, and flood protection standards in the analysis. We find substantial variability between the flood hazard maps in modelled inundated area and exposed GDP across multiple return periods (ranging from 5 to 1500 years) and in expected annual exposed GDP. For example, for the 100 year return period undefended (assuming no flood protection) hazard maps the percentage of total affected GDP of China ranges between 4.4 % and 10.5 % for fluvial floods. For the majority of the GFMs we see only a small increase in inundated area or exposed GDP for high return period undefended hazard maps compared to low return periods, highlighting major limitations in the models’ resolution and their output. The inclusion of industry models which currently model flooding at higher spatial resolution, and which additionally include pluvial flooding, strongly improves the comparison and provides important new benchmarks. Pluvial flooding can increase the expected annual exposed GDP by as much as 1.3 % points. Our study strongly highlights the importance of flood defenses for a realistic risk assessment in countries like China that are characterized by high concentrations of exposure. Even an incomplete (1.74 % of area of China) but locally detailed layer of structural defenses in high exposure areas reduces the expected annual exposed GDP to fluvial and pluvial flooding from 4.1 % to 2.8 %.

Evidence of layered piezometry system within the Chalk aquifer in parts of SE England

2020 ◽  
pp. qjegh2019-175
Author(s):  
Ilias Karapanos ◽  
Mahmoud Jaweesh ◽  
Daniel R. Yarker ◽  
Robert C. Sage ◽  
Alessandro Marsili ◽  
...  
Keyword(s):  
Groundwater Level ◽  
Environmental Sustainability ◽  
Regional Scale ◽  
Water Levels ◽  
Layered System ◽  
Lithostratigraphic Units ◽  
Support Tools ◽  
Multi Level ◽  
Chalk Aquifer ◽  
Deep Boreholes

The Chalk aquifer is often considered as a single, homogeneous, isotropic groundwater system in regional groundwater management studies, even though it has been subdivided into several different lithostratigraphic units. Low-permeability layers, including marl bands and hardgrounds, extend on a regional scale and define different layers within the Chalk. Four case studies in different locations of the Chalk aquifer of SE England are presented: (1) a multi-level observation borehole in the Upper Colne catchment in Hertfordshire; (2) different water levels in shallow and deep boreholes in the River Ver catchment; (3) artesian conditions and rises in the groundwater level during drilling in the Chiltern Hills; and (4) groundwater level separation in a public water supply borehole in Kent. The evidence clearly shows a layered system in the Chalk and vertical hydraulic discontinuity within the studied sequences. The current conceptual model of the Chalk aquifer should be enhanced to include this new understanding and to update the existing numerical groundwater models. This will, in turn, increase confidence in the current decision support tools for environmental sustainability and the management of water resources in the Chalk aquifer.

scholarly journals Flood forecasting using a coupled hydrological and hydraulic model (based on FVM) and highresolution meteorological model

2018 ◽  
Vol 40 ◽  
pp. 06028 ◽  
Author(s):  
Marcos Sanz-Ramos ◽  
Arnau Amengual ◽  
Ernest Bladé ◽  
Romu Romero ◽  
Hélène Roux
Keyword(s):  
Flood Risk ◽  
Overland Flow ◽  
Extreme Rainfall ◽  
Flood Forecasting ◽  
Water Levels ◽  
Flood Risk Assessment ◽  
Flood Events ◽  
Risk Models ◽  
Meteorological Model ◽  
Risk Assessment And Management

A forecasting systems based on the coupling of meteorological, hydrologic, hydraulic and risk models is used to minimize the risks associated to water scarcity and flooding. The fulfilment of such complex forecasting chains can allow obtaining information of the most plausible scenarios of water and risk management up to 96 hours ahead. In the present work, flood forecasting was carried out for different events in the upper La Muga basin (including the reservoir), within the European project “Flood Risk Assessment and Management in the Pyrenees” (http://pgriepm. eu/). The main purpose of the project was to develop a method to optimize the management of flood scenarios in order to minimize the flood risk while maximizing the water resources. The good fit of all the models, obtaining the forecasting rainfall and converting the overland flow in water levels in the reservoir, can give tools and important information to the authorities or dam managers for suitable management during the extreme rainfall and flood events.

scholarly journals Sustainable Floodplains: Linking E-Flows to Floodplain Management, Ecosystems, and Livelihoods in the Sahel of North Africa

2020 ◽  
Vol 12 (24) ◽  
pp. 10578
Author(s):  
Gordon C. O’Brien ◽  
Chris Dickens ◽  
Chris Baker ◽  
Retha Stassen ◽  
Frank van Weert
Keyword(s):  
North Africa ◽  
Water Resource Management ◽  
Regional Scale ◽  
Water Levels ◽  
Low Flow ◽  
Floodplain Management ◽  
Ecological Consequences ◽  
Development Scenarios ◽  
Sustainable Services ◽  
Sahel Region

Floodplains are particularly important in the semi-arid region of the Sub-Sahelian Africa. In this region, water governance is still being developed, often without adequate information and technical capacity for good, sustainable water resource management. However, water resources are being allocated for use with minimal sustainability considerations. Environmental flows (e-flows) include the quantity and timing of flows or water levels needed to meet the sustainable requirements of freshwater and estuarine ecosystems. Holistic regional scale e-flows linked to floodplain management can make a noticeable contribution to sustainable floodplain management. The Inner Niger Delta (IND) in Mali is an example of a vulnerable, socio-ecologically important floodplain in the Sahel region of North Africa that is being developed with little understanding of sustainability requirements. Although integrally linked to the Upper Niger River catchment, the IND sustains a million and half people within the region and exports food to surrounding areas. The flooding of the Delta is the engine of the socio-economic development as well as its ecological integrity. This paper aims to demonstrate the contribution that holistic regional e-flow assessment using the PROBFLO approach has to achieving floodplain sustainability. This can be achieved through the determining the e-flow requirements to maintain critical requirements of the ecosystems and associated services used by local vulnerable human communities for subsistence and describing the socio-ecological consequences of altered flows. These outcomes can contribute to the management of the IND. In this study, the socio-ecological consequences of altered flows have been evaluated by assessing the risk of alterations in the volume, duration, and timing of flows, to a number of ecological and social endpoints. Based on the risk posed to these endpoints by each scenario of change, an e-flow of 58% (26,685 million cubic meters (MCM) of water annually) was determined that would protect the ecosystem and maintain indicator components at a sustainable level. These e-flows also provide sustainable services to local communities including products for subsistence and limit any abnormal increases in diseases to the vulnerable African communities who live in the basin. Relative risk outputs for the development scenarios result in low-to-high-risk probabilities for most endpoints. The future development scenarios include insufficient flows to maintain sustainability during dry or low-flow periods with an increase in zero flow possibilities. Although unsuitable during the low-flow or dry periods, sufficient water is available through storage in the basin to meet the e-flows if these scenarios were considered for implementation. The IND is more vulnerable to changes in flows compared to the rivers upstream of the IND. The e-flow outcomes and consequences of altered flow scenarios has contributed to the management of vulnerable IND floodplains and the requirements and trade-off considerations to achieve sustainability.

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