Flood Hazard Mapping with Distributed Hydrological Simulations and Remote-Sensed Slackwater Sediments in Ungauged Basins

We present a basin-scale method to assimilate hydrological data from remote-sensed flood evidence and map civil infrastructures with risk of flooding. As in many rural areas with a semi-arid climate, the studied catchments do not contain stream gauge, and precipitation data does not capture the spatial variability of extreme hydrological events. Remote-sensed flood evidence as slackwater sediments were available at the whole basin, allowing the paleohydrological reconstruction at many sites across the catchment. The agreement between the predicted and observed inundation area was excellent, with an error lower than 15% on average. In addition, the simulated elevations overlapped the observed values in the flooded areas, showing the accuracy of the method. The peak discharges that provoked floods recorded the spatial variability of the precipitation. The variation coefficients of the rainfall intensity were 30% and 40% in the two studied basins with a mean precipitation rate of 3.1 and 4.6 mm/h, respectively. The assumption of spatially uniform precipitation leads to a mean error of 20% in evaluating the local water discharges. Satellite-based rainfall underpredicted the accumulated precipitation by 30–85.5%. Elaborating an inventory of the civil infrastructures at risk was straightforward by comparing the water surface elevation and transport network. The reconstructed maps of rainfall rate were used in the distributed hydrological model IBERPLUS to this end. Recent flood events that overtopped the infrastructures at risk verified our predictions. The proposed research methods can be easily applied and tested in basins with similar physical characteristics around the Mediterranean region.

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A metric-based assessment of flood risk and vulnerability of rural communities in the Lower Shire Valley, Malawi

Proceedings of the International Association of Hydrological Sciences ◽

10.5194/piahs-370-139-2015 ◽

2015 ◽

Vol 370 ◽

pp. 139-145 ◽

Cited By ~ 6

Author(s):

A. J. Adeloye ◽

F. D. Mwale ◽

Z. Dulanya

Keyword(s):

Rural Communities ◽

Spatial Variability ◽

Flood Risk ◽

Flood Hazard ◽

Sub Saharan Africa ◽

Structured Interviews ◽

Adaptation Measures ◽

Flood Depth ◽

Inundation Area ◽

Sub Saharan

Abstract. In response to the increasing frequency and economic damages of natural disasters globally, disaster risk management has evolved to incorporate risk assessments that are multi-dimensional, integrated and metric-based. This is to support knowledge-based decision making and hence sustainable risk reduction. In Malawi and most of Sub-Saharan Africa (SSA), however, flood risk studies remain focussed on understanding causation, impacts, perceptions and coping and adaptation measures. Using the IPCC Framework, this study has quantified and profiled risk to flooding of rural, subsistent communities in the Lower Shire Valley, Malawi. Flood risk was obtained by integrating hazard and vulnerability. Flood hazard was characterised in terms of flood depth and inundation area obtained through hydraulic modelling in the valley with Lisflood-FP, while the vulnerability was indexed through analysis of exposure, susceptibility and capacity that were linked to social, economic, environmental and physical perspectives. Data on these were collected through structured interviews of the communities. The implementation of the entire analysis within GIS enabled the visualisation of spatial variability in flood risk in the valley. The results show predominantly medium levels in hazardousness, vulnerability and risk. The vulnerability is dominated by a high to very high susceptibility. Economic and physical capacities tend to be predominantly low but social capacity is significantly high, resulting in overall medium levels of capacity-induced vulnerability. Exposure manifests as medium. The vulnerability and risk showed marginal spatial variability. The paper concludes with recommendations on how these outcomes could inform policy interventions in the Valley.

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GIS-Based Flood Hazard Mapping in Itang District of the Gambella Region, Ethiopia

10.21203/rs.3.rs-430787/v1 ◽

2021 ◽

Author(s):

Dame Tadesse ◽

Venkata Suryabhagavan Karuturi ◽

Dessie Nedaw

Keyword(s):

Global Economy ◽

Flood Hazard ◽

Gumbel Distribution ◽

Extreme Value ◽

Hazard Mapping ◽

Distribution Models ◽

Inundation Area ◽

Pearson Type ◽

Gis Data ◽

Log Normal

Abstract Flood is one of the natural disasters that affect societies around the world. Every year, flood claims hundreds of human lives and causes damage to the global economy and environment. Consequently, the identification of flood-vulnerable areas is important for comprehensive flood risk management. This study aims to delineate flood hazard areas in Itang District of Gambella Region, Ethiopia, applying the Gumbel probability distribution and Analytical Hierarchy Process (AHP) method. Distribution models applied in the study involve the generalized extreme value, Gumbel, Log-Normal, and Log Pearson type III. The Gumbel distribution provides the best fit according to the extreme value analyses. After obtaining discharge level through the method, the region's flood inundation area was mapped at 5, 10, 25, 50, and 100-year recurrence intervals. The developed methodology processes six parameters, namely, slope, elevation, land-use/land-cover, rainfall, discharge, and soil. Each criterion was evaluated with the aid of AHP and mapped by GIS. Data were assorted into five suitability classes, viz., very high, high, moderate, low, and very low flooding areas, representing 29.7%, 27.8%, 18.5%, 12.7%, and 11.4%, respectively. The outcome is extremely useful for evacuation planning, damage assessment, and losses estimation, thereby minimizing the natural disaster's effect in the study area.

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