Application of Active Space-Borne Microwave Remote Sensing in Flood Hazard Management

Satellite remote sensing is a powerful tool to map flooded areas. In recent years, the availability of free satellite data significantly increased in terms of type and frequency, allowing the production of flood maps at low cost around the world. In this work, we propose a semi-automatic method for flood mapping, based only on free satellite images and open-source software. The proposed methods are suitable to be applied by the community involved in flood hazard management, not necessarily experts in remote sensing processing. As case studies, we selected three flood events that recently occurred in Spain and Italy. Multispectral satellite data acquired by MODIS, Proba-V, Landsat, and Sentinel-2 and synthetic aperture radar (SAR) data collected by Sentinel-1 were used to detect flooded areas using different methodologies (e.g., Modified Normalized Difference Water Index, SAR backscattering variation, and supervised classification). Then, we improved and manually refined the automatic mapping using free ancillary data such as the digital elevation model-based water depth model and available ground truth data. We calculated flood detection performance (flood ratio) for the different datasets by comparing with flood maps made by official river authorities. The results show that it is necessary to consider different factors when selecting the best satellite data. Among these factors, the time of the satellite pass with respect to the flood peak is the most important. With co-flood multispectral images, more than 90% of the flooded area was detected in the 2015 Ebro flood (Spain) case study. With post-flood multispectral data, the flood ratio showed values under 50% a few weeks after the 2016 flood in Po and Tanaro plains (Italy), but it remained useful to map the inundated pattern. The SAR could detect flooding only at the co-flood stage, and the flood ratio showed values below 5% only a few days after the 2016 Po River inundation. Another result of the research was the creation of geomorphology-based inundation maps that matched up to 95% with official flood maps.

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Review of different methods and techniques used for flood vulnerability analysis

10.5194/nhess-2020-297 ◽

2020 ◽

Author(s):

Dilip Kumar ◽

Rajib Kumar Bhattacharjya

Keyword(s):

Vulnerability Assessment ◽

Flood Hazard ◽

Ground Level ◽

Primary Objective ◽

Single Type ◽

Flood Vulnerability ◽

Hazard Management ◽

Multiple Risks ◽

Flood Hazard Management ◽

Precise Relationship

Abstract. Assessment of vulnerability is the primary objective of ﬂood hazard management. One of the most signiﬁcant purposes of ﬂood vulnerability appraisal is to make a precise relationship between the theoretical conceptions of ﬂood vulnerability and the ground level management policies. A variety of approaches have been defined by many researchers to evaluate vulnerability. As such, the selection of the most suitable methodology is essential for policymakers to adequate mitigation policies. The purpose of the present study is to review all the vulnerability methods floating over the research universe and compare their beneﬁts and drawbacks. This study evaluated more than 250 selected articles related to the assessment of vulnerability published between 1980 and 2020 to determine their competence in the estimation of flood vulnerability. The findings show that most of the research works are related to statistical methods, and the methods used to allocate weight to different indicators associate to the vulnerability. Moreover, most of the vulnerability assessment methods are centred around the single type of hazard, i.e., flood, drought, etc. As such, the results recommend the necessity for developing a new integrated vulnerability assessment framework applicable to worldwide considering multiple risks.

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