Quantifying the effect of dams in reducing global flood exposure under climate change

2021 ◽  
Author(s):  
Julien Boulange ◽  
Naota Hanasaki ◽  
Dai Yamazaki ◽  
Yadu Pokhrel
Keyword(s):  
Climate Change ◽  
Flood Risk ◽  
Greenhouse Gas Emission ◽  
Hydrological Cycle ◽  
Climate Change Impacts ◽  
Flood Protection ◽  
Population Exposure ◽  
Water Regulation ◽  
Catchment Scale ◽  
Flood Exposure

<p>Flood risk was reported to increase in the future due to climate change and population growth. While recent and earlier studies have derived plausible climate change impacts on global flood risk, dams have never been explicitly implemented into simulation tools. Currently, about half of major river systems worldwide are regulated by dams and more than 3,700 major dams are planned or under construction. Consequently, to realistically assess population exposure to present and future floods, current and future dam landscapes must be integrated into existing flood modeling frameworks.</p><p>In this research, the role of dams on future flood risk under climate change is quantified by simulating the global hydrological cycle, including floodplain dynamics, and considering flow regulation by dams.</p><p> </p><p>The global population exposed to historical once-in-100-year floods in our simulation was 9.4 million people, relatively close to the estimate of 5.6 million people indicated in a previous study (Hirabayashi et al., 2013) and the Dartmouth Flood Observatory database which estimated this number as 11.9 million people. Downstream of dams, the number of people exposed to the historical once-in-100-year floods were 7.2 and 13.4 million on average over 2006–2099 given a low and a medium-high greenhouse gas emission trajectory (RCP2.6 and RCP6.0, respectively). By the end of the 21<sup>st</sup> century, the populations exposed to flooding below dams decreased on average by 20.6% and 12. 9% for the two trajectories compared to simulations not accounting for the flow regulations produced by dams.</p><p>At the catchment scale, by considering water regulation in densely populated and heavily water regulated catchments, the occurrence of flood events largely decreases compared to projections not accounting for water regulation. Over the 2070–2099 period and for 14 catchments, the annual flooded area shrank by, on average (first and third quartiles given in bracket), 22.5% (19.8–40.5) and 25.9% (12.1–34.5) for RCP2.6 and RCP6.0 respectively.</p><p>To maintain the levels of flood protection that dams have provided, new dam operations will be required to offset the effect of climate change, possibly negatively affecting energy production and water storage. In addition, precise and reliable hydro-meteorological forecasts will be invaluable for enhancing flood protection and avoid excessive outflows. Given the many negative environmental and social impacts of dams, comprehensive assessments that consider both potential benefits and adverse effects are necessary for the sustainable development of water resources.</p>

scholarly journals Role of dams in reducing global flood exposure under climate change

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Julien Boulange ◽  
Naota Hanasaki ◽  
Dai Yamazaki ◽  
Yadu Pokhrel
Keyword(s):  
Climate Change ◽  
Population Growth ◽  
Flood Risk ◽  
Impact Analysis ◽  
Flow Regulation ◽  
Flood Mitigation ◽  
Population Exposure ◽  
Flood Exposure ◽  
Future Population

AbstractGlobally, flood risk is projected to increase in the future due to climate change and population growth. Here, we quantify the role of dams in flood mitigation, previously unaccounted for in global flood studies, by simulating the floodplain dynamics and flow regulation by dams. We show that, ignoring flow regulation by dams, the average number of people exposed to flooding below dams amount to 9.1 and 15.3 million per year, by the end of the 21st century (holding population constant), for the representative concentration pathway (RCP) 2.6 and 6.0, respectively. Accounting for dams reduces the number of people exposed to floods by 20.6 and 12.9% (for RCP2.6 and RCP6.0, respectively). While environmental problems caused by dams warrant further investigations, our results indicate that consideration of dams significantly affect the estimation of future population exposure to flood, emphasizing the need to integrate them in model-based impact analysis of climate change.

scholarly journals Coastal and river flood risk analyses for guiding economically optimal flood adaptation policies: a country-scale study for Mexico

2018 ◽  
Vol 376 (2121) ◽  
pp. 20170329 ◽  
Author(s):  
Toon Haer ◽  
W. J. Wouter Botzen ◽  
Vincent van Roomen ◽  
Harry Connor ◽  
Jorge Zavala-Hidalgo ◽  
...  
Keyword(s):  
Climate Change ◽  
Risk Assessment ◽  
Flood Risk ◽  
Cost Benefit ◽  
Economic Benefits ◽  
Adaptation Strategies ◽  
Policy Implications ◽  
Flood Protection ◽  
Local Data ◽  
Flood Adaptation

Many countries around the world face increasing impacts from flooding due to socio-economic development in flood-prone areas, which may be enhanced in intensity and frequency as a result of climate change. With increasing flood risk, it is becoming more important to be able to assess the costs and benefits of adaptation strategies. To guide the design of such strategies, policy makers need tools to prioritize where adaptation is needed and how much adaptation funds are required. In this country-scale study, we show how flood risk analyses can be used in cost–benefit analyses to prioritize investments in flood adaptation strategies in Mexico under future climate scenarios. Moreover, given the often limited availability of detailed local data for such analyses, we show how state-of-the-art global data and flood risk assessment models can be applied for a detailed assessment of optimal flood-protection strategies. Our results show that especially states along the Gulf of Mexico have considerable economic benefits from investments in adaptation that limit risks from both river and coastal floods, and that increased flood-protection standards are economically beneficial for many Mexican states. We discuss the sensitivity of our results to modelling uncertainties, the transferability of our modelling approach and policy implications. This article is part of the theme issue ‘Advances in risk assessment for climate change adaptation policy’.

scholarly journals Climate change impacts on hydrology and water resources of Indian River basin

2018 ◽  
Vol 13 (1) ◽  
pp. 32-43 ◽  
Author(s):  
Umesh Kumar Singh ◽  
Balwant Kumar
Keyword(s):  
Climate Change ◽  
Groundwater Recharge ◽  
River Basin ◽  
Greenhouse Gas Emission ◽  
Hydrological Cycle ◽  
Indian Subcontinent ◽  
Climatic Variability ◽  
River Basins ◽  
Extreme Weather Events ◽  
Runoff Generation

Anthropogenic greenhouse gas emission is altering the global hydrological cycle due to change in rainfall pattern and rising temperature which is responsible for alteration in the physical characteristics of river basin, melting of ice, drought, flood, extreme weather events and alteration in groundwater recharge. In India, water demand for domestic, industrial and agriculture purposes have already increased many folds which are also influencing the water resource system. In addition, climate change has induced the surface temperature of the Indian subcontinent by 0.48 ºC in just last century. However, Ganges–Brahmaputra–Meghna (GBM) river basins have great importance for their exceptional hydro-geological settings and deltaic floodplain wetland ecosystems which support 700 million people in Asia. The climatic variability like alterations in precipitation and temperature over GBM river basins has been observed which signifies the GBM as one of the most vulnerable areas in the world under the potential impact of climate change. Consequently, alteration in river discharge, higher runoff generation, low groundwater recharge and melting of glaciers over GBM river basin could be observed in near future. The consequence of these changes due to climate change over GBM basin may create serious water problem for Indian sub-continents. This paper reviews the literature on the historical climate variations and how climate change affects the hydrological characteristics of different river basins.

scholarly journals Satellites, Self-reports, and Submersion: Exposure to Floods in Bangladesh

2015 ◽  
Vol 105 (5) ◽  
pp. 232-236 ◽  
Author(s):  
Raymond Guiteras ◽  
Amir Jina ◽  
A. Mushfiq Mobarak
Keyword(s):  
Climate Change ◽  
Economic Activity ◽  
Climate Change Impacts ◽  
Objective Data ◽  
Short Term ◽  
Temperature And Precipitation ◽  
Flood Exposure ◽  
Self Reports ◽  
Term Variation

A burgeoning “Climate-Economy” literature has uncovered many effects of changes in temperature and precipitation on economic activity, but has made considerably less progress in modeling the effects of other associated phenomena, like natural disasters. We develop new, objective data on floods, focusing on Bangladesh. We show that rainfall and self-reported exposure are weak proxies for true flood exposure. These data allow us to study adaptation, giving accurate measures of both long-term averages and short term variation in exposure. This is important in studying climate change impacts, as people will not only experience new exposures, but also experience them differently.

scholarly journals Assessing the Effectiveness of Supplemental Irrigation to Improve Soil Moisture in an Arid Ecosystem with an Emphasis on Climate Change: A Case Study from the State of Kuwait

2020 ◽  
Vol 12 (21) ◽  
pp. 9104
Author(s):  
Ahmed Alqallaf ◽  
Bader Al-Anzi ◽  
Meshal Alabdullah
Keyword(s):  
Climate Change ◽  
Soil Moisture ◽  
Hydrological Cycle ◽  
Winter Season ◽  
Climate Change Impacts ◽  
Summer Season ◽  
Arid Ecosystems ◽  
Arid Ecosystem ◽  
Supplemental Irrigation ◽  
The State Of Kuwait

Arid ecosystems are extremely vulnerable to climate change, which is considered one of the serious global environmental issues that can cause critical challenges to the hydrological cycle in arid ecosystems. This work focused on assessing the effectiveness of supplemental irrigation to improve the actual soil moisture content in arid ecosystems and considering climate change impacts on soil moisture. The study was conducted at two fenced protected sites in Kuwait. The first site is naturally covered with Rhanterietum epapposum, whereas the other study site is a supplemented irrigated site, containing several revegetated native plants. The results showed that supplemental irrigation highly improved soil moisture (∆SM) during the winter season by >50%. However, during the summer season, the rainfed and irrigated site showed low ∆SM due to the high temperature and high evapotranspiration (ET) rates. We also found that ∆SM would negatively get impacted by climate change. The climate change projection results showed that temperature would increase by 12%–23%, ET would increase by 17%–19%, and precipitation would decrease by 31%–46% by 2100. Such climate change impacts may also shift the current ecosystem from an arid to a hyper-arid ecosystem. Therefore, we concluded that irrigation is a practical option to support the ∆SM during the low-temperature months only (spring and winter) since the results did not show any progress during the summer season. It is also essential to consider the possibility of future shifting in ecosystems and plant communities in restoration and revegetation planning.

scholarly journals Water-level attenuation in broad-scale assessments of exposure to coastal flooding: a sensitivity analysis

2018 ◽  
Author(s):  
Athanasios T. Vafeidis ◽  
Mark Schuerch ◽  
Claudia Wolff ◽  
Tom Spencer ◽  
Jan L. Merkens ◽  
...  
Keyword(s):  
Water Level ◽  
Flood Risk ◽  
Land Surface ◽  
Surface Characteristics ◽  
Water Levels ◽  
Risk Indicators ◽  
Population Exposure ◽  
Modelling Framework ◽  
Complex Interactions ◽  
Flood Exposure

Abstract. This study explores the uncertainty introduced in global assessments of coastal flood exposure and risk when not accounting for water level attenuation due to land-surface characteristics. We implement a range of plausible water-level attenuation values for characteristic land-cover classes in the flood module of the Dynamic and Integrated Vulnerability Assessment (DIVA) modelling framework and assess the sensitivity of flood exposure and flood risk indicators to differences in attenuation rates. Results show a reduction of up to 47 % in area exposure and even larger reductions in population exposure and expected flood damages when considering water level attenuation. The reductions vary by country, reflecting the differences in the physical characteristics of the floodplain as well as in the spatial distribution of people and assets in coastal regions. We find that uncertainties related to not accounting for water attenuation in global assessments of flood risk are of similar magnitude to the uncertainties related to the amount of SLR expected over the 21st century. Despite using simplified assumptions to account for the process of water level attenuation, which depends on numerous factors and their complex interactions, our results strongly suggest that an improved understanding and representation of the temporal and spatial variation of water levels across floodplains is essential for future impact modelling.

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