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

2019 ◽  
Vol 19 (5) ◽  
pp. 973-984 ◽  
Author(s):  
Athanasios T. Vafeidis ◽  
Mark Schuerch ◽  
Claudia Wolff ◽  
Tom Spencer ◽  
Jan L. Merkens ◽  
...  
Keyword(s):  
Water Level ◽  
Flood Risk ◽  
Land Surface ◽  
Surface Characteristics ◽  
Global Scale ◽  
Water Levels ◽  
Risk Indicators ◽  
Population Exposure ◽  
Modelling Framework ◽  
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 44 % 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 sea-level rise 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.

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.

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

2017 ◽  
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 by not accounting for water level attenuation due to land–surface characteristics. We implement a range of plausible water level attenuation values in the flood module of the Dynamic Interactive 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. Despite the use of a spatially constant rate for water 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 the omission of this factor 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, as the process of water level attenuation depends on numerous factors and their complex interactions, our results strongly suggest that future impact modelling needs to focus on an improved representation of the temporal and spatial variation of water levels across floodplains by incorporating the effects of relevant processes.

scholarly journals Feedback Mechanism in Bifurcating River Systems: the Effect on Water-Level Sensitivity

Water ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1915
Author(s):  
Matthijs R.A. Gensen ◽  
Jord J. Warmink ◽  
Fredrik Huthoff ◽  
Suzanne J.M.H. Hulscher
Keyword(s):  
Water Level ◽  
Flood Risk ◽  
River System ◽  
Feedback Mechanism ◽  
Water Levels ◽  
River Systems ◽  
Water Level Variations ◽  
System Water ◽  
Discharge Distribution ◽  
Single Branch

Accurate and reliable estimates of water levels are essential to assess flood risk in river systems. In current practice, uncertainties involved and the sensitivity of water levels to these uncertainties are studied in single-branch rivers, while many rivers in deltas consist of multiple distributaries. In a bifurcating river, a feedback mechanism exists between the downstream water levels and the discharge distribution at the bifurcation. This paper aims to quantify the sensitivity of water levels to main channel roughness in a bifurcating river system. Water levels are modelled for various roughness scenarios under a wide range of discharge conditions using a one-dimensional hydraulic model. The results show that the feedback mechanism reduces the sensitivity of water levels to local changes of roughness in comparison to the single-branch river. However, in the smaller branches of the system, water-level variations induced by the changes in discharge distribution can exceed the water-level variations of the single-branch river. Therefore, water levels throughout the entire system are dominated by the conditions in the largest branch. As the feedback mechanism is important, the river system should be considered as one interconnected system in river maintenance of rivers, flood-risk analyses, and future planning of river engineering works.

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 A high resolution global scale groundwater model

2014 ◽  
Vol 11 (5) ◽  
pp. 5217-5250 ◽  
Author(s):  
I. E. M. de Graaf ◽  
E. H. Sutanudjaja ◽  
L. P. H. van Beek ◽  
M. F. P. Bierkens
Keyword(s):  
Groundwater Flow ◽  
Land Surface ◽  
Regional Scale ◽  
Land Surface Model ◽  
Global Scale ◽  
Water Levels ◽  
Natural State ◽  
Surface Model ◽  
Groundwater Model ◽  
Aquifer Systems

Abstract. Groundwater is the world's largest accessible source of fresh water. It plays a vital role in satisfying needs for drinking water, agriculture and industrial activities. During times of drought groundwater sustains baseflow to rivers and wetlands, thereby supporting ecosystems. Most global scale hydrological models (GHMs) do not include a groundwater flow component, mainly due to lack of geohydrological data at the global scale. For the simulation of lateral flow and groundwater head dynamics a realistic physical representation of the groundwater system is needed, especially for GHMs that run at finer resolution. In this study we present a global scale groundwater model (run at 6' as dynamic steady state) using MODFLOW to construct an equilibrium water table at its natural state as the result of long-term climatic forcing. The aquifer schematization and properties were based on available global datasets of lithology and transmissivities combined with estimated aquifer thickness of an upper unconfined aquifer. The model is forced with outputs from the land-surface model PCR-GLOBWB, specifically with net recharge and surface water levels. A sensitivity analysis, in which the model was run with various parameter settings, showed variation in saturated conductivity causes most of the groundwater level variations. Simulated groundwater heads were validated against reported piezometer observations. The validation showed that groundwater depths are reasonably well simulated for many regions of the world, especially for sediment basins (R2 = 0.95). The simulated regional scale groundwater patterns and flowpaths confirm the relevance of taking lateral groundwater flow into account in GHMs. Flowpaths show inter-basin groundwater flow that can be a significant part of a basins water budget and helps to sustain river baseflow, explicitly during times of droughts. Also important aquifer systems are recharged by inter-basin groundwater flows that positively affect water availability.

scholarly journals Global riverine flood risk – how do hydrogeomorphic floodplain maps compare to flood hazard maps?

2021 ◽  
Vol 21 (10) ◽  
pp. 2921-2948
Author(s):  
Sara Lindersson ◽  
Luigia Brandimarte ◽  
Johanna Mård ◽  
Giuliano Di Baldassarre
Keyword(s):  
High Resolution ◽  
Flood Risk ◽  
Flood Hazard ◽  
Global Scale ◽  
Research Centre ◽  
Hazard Maps ◽  
Joint Research ◽  
Flood Exposure ◽  
Population Grid ◽  
Flood Hazard Maps

Abstract. Riverine flood risk studies often require the identification of areas prone to potential flooding. This modelling process can be based on either (hydrologically derived) flood hazard maps or (topography-based) hydrogeomorphic floodplain maps. In this paper, we derive and compare riverine flood exposure from three global products: a hydrogeomorphic floodplain map (GFPLAIN250m, hereinafter GFPLAIN) and two flood hazard maps (Flood Hazard Map of the World by the European Commission's Joint Research Centre, hereinafter JRC, and the flood hazard maps produced for the Global Assessment Report on Disaster Risk Reduction 2015, hereinafter GAR). We find an average spatial agreement between these maps of around 30 % at the river basin level on a global scale. This agreement is highly variable across model combinations and geographic conditions, influenced by climatic humidity, river volume, topography, and coastal proximity. Contrary to expectations, the agreement between the two flood hazard maps is lower compared to their agreement with the hydrogeomorphic floodplain map. We also map riverine flood exposure for 26 countries across the global south by intersecting these maps with three human population maps (Global Human Settlement population grid, hereinafter GHS; High Resolution Settlement Layer, hereinafter HRSL; and WorldPop). The findings of this study indicate that hydrogeomorphic floodplain maps can be a valuable way of producing high-resolution maps of flood-prone zones to support riverine flood risk studies, but caution should be taken in regions that are dry, steep, very flat, or near the coast.

scholarly journals Flood mapping under an extreme event in a large shallow lake influenced by flood pulse in Southeast Asia

2020 ◽  
Vol 148 ◽  
pp. 06004
Author(s):  
Sokly Siev ◽  
Vannak Ann ◽  
Takashi Nakamura ◽  
Hideto Fujii ◽  
Chihiro Yoshimura
Keyword(s):  
Southeast Asia ◽  
Water Level ◽  
Shallow Lake ◽  
Flood Risk ◽  
Extreme Event ◽  
Gumbel Distribution ◽  
Flood Pulse ◽  
Water Levels ◽  
Mekong River ◽  
Flood Mapping

Tonle Sap Lake (TSL) in Cambodia is the largest shallow lake in Southeast Asia. Influenced by flood pulse system of the Mekong River, TSL provides diverse benefits including ecosystem services, ecological functioning, and flood water storage in the floodplains. However, extreme events (e.g., flooding) due to rising water level caused by dam break and/or heavy rainfall in the Mekong River Basin could threaten the ecosystems of the lake, community health and economic growth in the region. Flood mapping under such extreme event could be informative in the flood risk and emergency management. In this study, we aim to develop a flood risk boundary map in TSL using an existing 2D hydrodynamic model (Caesar-Lisflood, CL) with rising water levels estimated by Gumbel distribution. As a result, the extreme water level of 1% chance (or 100-year flood return period) exceeding the annual maximum water level at Prek Kdam station was approximately 11.38 m resulting in the largest inundation area of 15193 km2. Overall, the employed method and flood risk mapping are useful for the decision makers to manage flood risks and emergency in the lake. This is to anticipate the consequences of a possible rising water level by an extreme event.

scholarly journals Characterization of SWOT Water Level Errors on Seine Reservoirs and La Bassée Gravel Pits: Impacts on Water Surface Energy Budget Modeling

2020 ◽  
Vol 12 (18) ◽  
pp. 2911
Author(s):  
Catherine Ottlé ◽  
Anthony Bernus ◽  
Thomas Verbeke ◽  
Karine Pétrus ◽  
Zun Yin ◽  
...  
Keyword(s):  
Water Level ◽  
Measurement Errors ◽  
Water Reservoir ◽  
Global Scale ◽  
Water Levels ◽  
Surface Energy Budget ◽  
Water Bodies ◽  
Energy Budgets ◽  
Gravel Pits ◽  
Better Than

The Surface Water and Ocean Topography (SWOT) space mission will map surface area and water level changes in lakes at the global scale. Such new data are of great interest to better understand and model lake dynamics as well as to improve water management. In this study, we used the large-scale SWOT simulator developed at the French Space National Center (CNES) to estimate the expected measurement errors of the water level of different water bodies in France. These water bodies include five large reservoirs of the Seine River and numerous small gravel pits located in the Seine alluvial plain of La Bassée upstream of the city of Paris. The results show that the SWOT mission will allow to observe water levels with a precision of a few tens of centimeters (10 cm for the largest water reservoir (Orient), 23 km2), even for the small gravel pits of size of a few hectares (standard deviation error lower than 0.25 m for water bodies larger than 6 ha). The benefit of the temporal sampling for water level monitoring is also highlighted on time series of pseudo-observations based on real measurements perturbed with the simulated noise errors. Then, the added value of these future data for the simulation of lake energy budgets is shown using the FLake lake model through sensitivity experiments. Results show that the SWOT data will help to model the surface temperature of the studied water bodies with a precision better than 0.5 K and the evaporation with an accuracy better than 0.2 mm/day. These large improvements compared to the errors obtained when a constant water level is prescribed (1.2 K and 0.6 mm/day) demonstrate the potential of SWOT for monitoring the lake energy budgets at global scale in addition to the other foreseen applications in operational reservoir management.

Changes in hydrologic conditions in the Dixie Valley and Fairview Valley areas, Nevada, after the earthquake of December 16, 1954

1957 ◽  
Vol 47 (4) ◽  
pp. 387-396
Author(s):  
C. P. Zones
Keyword(s):  
Ground Water ◽  
Water Level ◽  
Land Surface ◽  
Water Levels ◽  
Temporary Increase ◽  
Valley Fill ◽  
Dixie Valley ◽  
Main Fault ◽  
Hydrologic Conditions ◽  
Total Discharge

abstract The earthquake of December 16, 1954, affected hydrologic conditions in the Dixie Valley and Fairview Valley areas, Nevada. In Dixie Valley the rate of flow of water from wells was temporarily increased and water flowed for more than a month from several wells that had not flowed before. Water levels in wells were higher after the earthquake, but the trend of water levels since the earthquake has varied locally. There is no evidence that ground-water temperatures were affected. The flow of Mud Springs, which is on the main fault on the west side of Dixie Valley, increased substantially immediately after the earthquake, but since has decreased to essentially its pre-earthquake rate. The water level in Fairview Valley was about 4 feet higher after the earthquake. In East Gate Valley and at West Gate, ground-water levels were lower after the earthquake. In June, 1956, the water level in East Gate Valley was 34 feet lower than the pre-earthquake level. At West Gate the water level was about 9 feet lower. In Stingaree Valley the water level began to rise after an initial decline and reached a peak about 11 feet higher than the pre-earthquake level. Possible causes for the rise in ground-water levels in Dixie and Fairview Valleys include tilting of the confined and semiconfined aquifers in the valleys, compaction of the sediments of the valley fill, and increased upward leakage of ground water. It is possible that opening of new fractures and widening of pre-existing fractures in the bedrock between East Gate, Cowkick, and Stingaree valleys has accelerated the rate of movement of ground water between those valleys. The temporary increase in the flow of water from Mud Springs may be due to the opening of fractures in the fault zone along which the water is rising, or to a possible lowering of the land surface at the springs with a resulting increase in artesian head at the spring orifices. It is thought that any increase in the total discharge of ground water in the Dixie Valley and Fairview Valley areas is temporary because the increased discharge is probably from ground-water storage.

scholarly journals Flood risk assessment of river “Kelani Ganga” exceeding its threshold water level

2020 ◽  
Vol 157 ◽  
pp. 02006
Author(s):  
Charith Dushyantha ◽  
Irina Ptuhina
Keyword(s):  
Risk Assessment ◽  
Water Level ◽  
Extreme Value Theory ◽  
Flood Risk ◽  
Value Theory ◽  
Extreme Value ◽  
Water Levels ◽  
Suitable Model ◽  
Flood Risk Assessment ◽  
Maximum Water

Flood risk assessment curves were developed for a flood risk assessment carried out in Colombo, Sri Lanka. Annual maximum water levels at three gauging stations in Kelani Ganga were used as data to prepare the flood risk assessment. Information sources include the Ministry of Disaster Management, Irrigation department and Department of Metrology. Current approaches to risk assessment function development were improved by using the extreme value theory. The most suitable model from the extreme value theory was defined by the behaviour of the probabilistic density function. The probability of a threshold water level exceeding in a given year can be predicted by using the developed model. According to the results of the flood risk assessment at the three gauging stations along river Kelani Ganga, the Hanwella station is at an 89.3% high risk of inundating the area with the water level reaching up to 9.6m in 10 years of time. These results can be used to develop hazard maps for these areas as one of the criteria that must be taken into consideration when choosing the optimal site for construction.

Sign in / Sign up

Export Citation Format

Share Document