A Review on Adaptation Practices of Affected People with Riverine Floods in Bangladesh

Bangladesh is a riverine country. Every year flood devastated Bangladesh. Therefore, response and adaptation strategies of flood affected people are important for planning future mitigation action. Present study focuses to review on adaptation practices of affected people with riverine floods in Bangladesh to reduce vulnerability of awaited flood. Consequently, they adopt several adaptation techniques by their life long experience. The major adaptation practiced of the people are raise homesteads using ‘dig-elevate-dwell’ principle of settlement, cultivate flood tolerant paddy (e.g. bona aman), cultivate vegetables in floating bed, tube well have been placed on an elevated base or raised with an additional pipe, and cementing the base of tube well. People also use their indigenous knowledge to cure diseases during flood. Hence, holy basil, and basak (Adhatoda Vasica) are used to treat colds and fevers. On the contrary, durba grass, gando badal (Gaultheria Fragrantissima), garden mint, and Indian pennywort are used for diarrhea and dysentery. Basically, people’s indigenous adaptation techniques have helped them to reduce damages of property and lives as well. Therefore, various types of adaptation should incorporate at the local level plan and implement by the concerned authority.

Increasing Timeliness of Satellite-Based Flood Mapping Using Early Warning Systems in the Copernicus Emergency Management Service

Remotely sensed images have become an important source of information for actors involved in disaster management and satellite-based emergency mapping (SEM) is increasingly used to support the response phase in the first hours and days after a disaster occurs. The delivery timeliness of the crisis information is key to the success of SEM. In the Copernicus Emergency Management Service (CEMS), a procedure was tested during the past 5 years which links the European Flood Awareness System (EFAS) with the on-demand Rapid Mapping module in order to anticipate satellite tasking in view of an upcoming activation of the service for riverine floods. This study aims at assessing if the procedure has helped to improve the delivery timeliness of the first flood impact information. For the assessment, we used the Rapid Mapping performance statistics recorded from June 2016 to December 2020. Standard Rapid Mapping activations for floods were compared with those preceded by an EFAS based pre-tasking request. The focus was on essential time stamps such as activation start, provision of imagery and the availability of derived information products. For the pre-tasking-related activations, we further compared the EFAS predictions with the Rapid Mapping user request and compared flood predictions with actual observations. Our results show that the EFAS based pre-tasking improves the timeliness of the first product delivery due to the fact that satellite images could be acquired earlier compared to activations without pre-tasking.

Environmental Inequalities in Flood Exposure: A Matter of Scale

Studies on inequalities in exposure to flood risk have explored whether population of a lower socio-economic status are more exposed to flood hazard. While evidence exist for coastal flooding, little is known on inequalities for riverine floods. This paper addresses two issues: (1) is the weakest population, in socio-economic terms, more exposed to flood hazard, considering different levels of exposure to hazard? (2) Is the exposure to flood risk homogeneous across the territory, considering different scales of analysis? An analysis of the exposure of inhabitants of Liège province to flood risk was conducted at different scales (province, districts, and municipalities), considering three levels of exposure to flood hazard (level 1- low hazard, level 3- high hazard), and five socio-economic classes (class 1-poorest, class 5-wealthiest households). Our analysis confirms that weaker populations (classes 2 and 3) are usually more exposed to flood hazards than the wealthiest (classes 4 and 5). Still it should be stressed that the most precarious households (class 1) are less exposed than low to medium-range ones (classes 2 and 3). Further on the relation between socio-economic status and exposure to flood hazard varies along the spatial scale considered. At the district level, it appears that classes 4 and 5 are most exposed to flood risk in some peripheral areas. In municipalities located around the center of the city, differences of exposure to risk are not significant.

Climate dominates changes in flood magnitude and timing across China during 1960-2017

<p>Riverine floods are exhibiting temporal shifts in both magnitude and timing under the context of climate change as well as human alternations of the river systems (i.e., construction of reservoirs and land management practices). A nation-wide assessment of changes in riverine floods is still lacking over China, despite the societal perception that recent Chinese flood trends are dictated by drastic environmental changes associated with rapid economic development. Here we examine changes in flood magnitude and timing based on the most comprehensive database of annual maximum flood peak discharge (AMF) over China during the period 1960-2017. We find both increasing and decreasing trends in AMF magnitude and timing. Trends in AMF magnitudes range from -4.29% to 2.86% (per year relative to long-term mean flood peak discharge). Decreased AMF magnitudes are observed in central and northern China, while increased AMF magnitudes mainly in northwestern and southern China. The shifts of AMF timing range from -16 days to +18 days per decade. Changes in AMF timing show less spatial consistency than that in AMF magnitude. We categorize the gauged watersheds into human-modified and natural categories. Flood changes in natural watersheds can only be attributed to climate variability. The spatial pattern of changes in AMF magnitude and timing in human-modified watersheds resembles those in natural watersheds, pointing towards the dominant role of climate in dictating recent flood changes over China. Impacts of reservoirs and land management practices are only isolated cases. We further provide a predictive understanding of climatic controls on flood hazards over China (and East Asian countries) by establishing connections between changes in AMF magnitude/timing and climate indices. Our analyses, together with similar efforts in other continents, contribute to a general understanding of space-time dynamics of riverine floods around the globe.</p>

A data-mining approach to investigate El Niño damage in Peru

<p>Compound natural hazards, like El Niño events, which trigger torrential rain, mudslides, riverine and flash floods, cause high damage to society. An improved risk management based on reliable risk assessments are urgently needed. However, knowledge about the complex processes leading to El Niño damage is lacking, and so are loss models.  We explore a large dataset of building damage from the coastal El Niño event 2017 in Peru. We use data-mining techniques to analyse data of damage grades of about 180.000 affected houses together with satellite observations and open geo-information. In a first step, we use unsupervised clustering (t-SNE + OPTICS) to separate regions of different dominant processes. Secondly, we train various supervised classification algorithms and create feature importance rankings per cluster, to identify drivers of observed damage for each of these regions. A comparison of different algorithms provides further insights about the potential and limitations of these methods and datasets. Results indicate that topographic wetness is the most important indicator, as selected by the algorithms, when using the entire dataset. Rainfall sum and maximum from TRMM satellite measurements are identified as damage driver despite the coarse spatial resolution. Also urbanity, based on a focal window around the global urban footprint, appears to play a role for the amount of damage. At least a coarse separation of processes is possible: the slope length and steepness, bare soil index, stream power index, and maximum rainfall are dominating the damage processes in lower mountain ranges and canyons, indicating rapid processes. Damage in upper mountain areas seem more influenced by the rainfall sum, local topographic position, and vegetation cover. In the lowlands, topographic wetness is very dominant, indicating ponding water or riverine floods. As opposed to previous work, this study constructs importance rankings based entirely on real observed damage to buildings. It is therefore a step towards data-driven damage assessments for El Niño events.</p>