A Review of Social Impact Assessment (SIA) and Flood Risk: Recommendations for the Management of Dam Disaster

The selected articles included in this research, which discussed SIA and flood risk or assessed social impact, are summarized and presented in Table 3, highlighting whether SIA was conducted, methodologies, and loss elements considered in the studies. Although, societal impact is frequently mentioned across the seventeen (17) studies. Only two studies [2, 26] practically assessed SIA, while four studies predicted social impact [9, 22, 27, 28] through social vulnerability or impact indexes [29]. One study assessed social impact as part of a comprehensive or integrated impact assessment, which considers not only social impacts but also economic and environmental losses, and whereas seven articles partially assessed social impact elements considering only a few loss elements [10, 11, 30-34]. For instance, some studies ignored educational impact and impact on cultural resources [10]; some studies only considered physical impact [11], population dynamics; some studies only considered social impact of post disaster infrastructure outrage [30]; some studies only considered impact on residential property [31-33]; some studies only considered infrastructural losses [34].

Besides that, two studies provided methodological frameworks, such as Aznar-Crespo et al. [8] offered complete guidelines for incorporating SIA into FRM, and Aqilah et al. [23] proposed a comprehensive framework for that includes social, economic, and environmental impact assessments based on United States’ Federal Emergency Management Agency (FEMA) damage factors which might not be fit to the countries with different socio-economic and environmental conditions. Among the literature, only two studies are related to dam disaster flood consequence assessment [22, 23]. The following Figure 2 shows the number of studies based on publication year and Figure 3 shows the countries of included studies.

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Figure 2. The number of studies based on publication year

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Figure 3. The countries of included studies

Table 3. Table showing review of included studie

As mentioned earlier, most reviewed studies assessed social impact elements partially considering only a few elements; some considered social loss elements under comprehensive or integrated impact assessments and economic and environmental elements. Some offered methodological or framework-based guidelines without practical assessment of SIA.

However, one review article provided a structured SIA assessment in the disaster management cycle beyond traditional post-disaster evaluations [8]. By adapting the IAIA's framework and reviewed concepts and methods from existing literature developed and proposed an SIA framework for management [8]. According to them, the adaptation of SIA in FRM may involve four key phases, shown in Figure 4.

1). Baseline study: to analyze the natural hazard characteristics, adaptive capacities of the potential exposure unit, and the social context;

2). Stakeholder analysis: To identify the prominent individuals and groups related to governance who have any interest in flood risk impacts and can facilitate effective communication and decision-making.

3). Impact identification and assessment: to identify the potential impacts and evaluate them, and

4). Impact management measures: After assessing the impacts, it is necessary to develop a strategic tool for policymakers and flood managers to enhance effective mitigation impact based on the significant of each loss.

Different studies used different processes for impact identification and assessment. For example, Yu et al. [2] applied a five-step process to evaluate socio-economic and environmental damage. First, they assessed flood risk using simulation models and remote sensing to analyze inundation, depth, and duration. Next, they gathered socio-economic and land-use data into a spatial database, followed by GIS overlay analysis to assess asset values across flood depths. In the fourth step, depth-damage rates were developed from historical data to estimate losses, which were then calculated using depth-to-loss ratios in the final step.

Besides that, other authors who mentioned the assessment framework, such as Righini et al. [27], also followed the key steps of assessment of hazard, understanding the flood exposure area, assessment of vulnerability, and finally assessing the impact index [23] also demonstrated assessment flow such as identifying flood characteristics variables, assessment of data and calculation of flood impact through scenario building analysis. However, upon reviewing the included studies we identified the commonly observed steps and stated in the Sections 3.1 to 3.5.

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Figure 4. Suggested phases of SIA in flood risk management (FRM) process [8]

3.1 Step one: Understanding the flood risk variables

Understanding key flood risk variables that are responsible for the degree of flood impact severity is the first step in any flood impact assessment study. Table 4 below depicts the list of flood characteristics variables discussed in the reviewed studies.

Table 4. Key flood risk variables

Most of the reviewed studies addressed flood depth, duration, inundation mapping, flood extent, and volume as significant variables in assessing flood risk impact. ‘Depth’ has been addressed as a flood risk variable in numerous research works [2, 23, 27, 33, 36]. Another important flood characteristic variable is the ‘duration’ of flooding [2, 23]. Flood inundation mapping, a term that defines the coverage of the flooded area, is also one of the predictive components of flood risk impact [2, 23, 36, 37]. Some other researchers [9, 36] addressed another important flood risk variable, "flood extent", which is a combination of flood depth and volume.

However, past studies mainly utilized flood simulation and numeric modelling to understand the nature of flood risks. For instance, Yu et al. [2] modelled flood hazards, including depths, durations and velocities through 2D hydro-hydraulic simulation models, remote sensing analysis, and field study. Pastor-Escuredo et al. [11] and used the Shuttle Radar Topography Mission (SRTM), Digital Elevation Model (DEM) to estimate the depth, and Afifi et al. [33], Gabriels et al. [36] also utilized DEM to determine flood extent. Righini et al. [27] applied Floodwater Depth Estimation Tool (FwDET-GEE) with multitemporal satellite imagery using Google Earth Engine along with high-resolution Digital Terrain Models (DTM) to map floodwater depth and forecast the inundation extents. Aqilah et al. [23] proposed analyzing flood risk variables- depth, duration, and area of inundation a scenario-building process to measure flood damage across high, medium, and low-risk scenarios. Also, Porter et al. [34] simulated the depth of flooding by a probabilistic method, calculating the expected depth level for each point of interest or asset. Whereas, Beck and Cha [30] used the Monte Carlo simulation technique.

3.2 Step two: Assessing socio-economic data of the exposure area

The second important phase of the study of flood risk impact is the socio-economic evaluation of the potential flood affected areas. This phase lays the foundation for understanding the potential impacts. This step includes assessment of socio-economic determinants such as demographic information [27, 37] and economic activities, income levels, employment status, and educational attainment of the occupants [2, 8, 36]. It also considers real estate values [2, 27], geographic features involving precipitation and topography [8, 11], and land use classes ranging from residential to commercial and industrial zones [2, 27, 33, 36]. The protected areas and suspected sources of contaminants [2] are also needed to assess to know the potential environmental impacts. The previous study mainly gathered these data from statistical yearbooks, field surveys with questionnaires, national and international databases, and GIS analysis. Table 5 presents an overview of the socio-economic and geographic factors to be considered in flood risk assessment, including probable sources of data collection.

Beyond assessment of socioeconomic conditions, previous studies also addressed some of the social vulnerability factors as contributing factors of flood risk impact severity [8, 9].

Social vulnerability factors include ‘demographic characteristics’ such as gender, age, the background of the family, race, ethnic background, and languages spoken [2, 8, 9]; ‘population density’ [9, 33]; and ‘socioeconomic status,’ which encompasses income, purchasing power, employment, education, and social capital [8, 9]. Additionally, ‘access to health services’ is also critical factor [8]. ‘Land tenure issues,’ including property structure, settlement regulation, housing quality, property markets, and insurance systems, further influence vulnerability [8]. Factors such as ‘proximity to rivers’ [33], ‘distance from emergency services’ like police and fire stations, and ‘neighborhood characteristics’ are also significant [8]. ‘Risk perception,’ or awareness of flood risks, past experiences, knowledge of self-protection measures, and trust in public institutions, also impacts the effectiveness of community responses against flood [8]. Finally, inadequate infrastructure and poorly maintained drainage systems, worsen flooding, particularly during heavy rainfall [9, 37]. The potential social vulnerability factors are depicted in Table 6.

Table 5. Socio-economic factors needed to assess before flood impact assessment

Table 6. Social vulnerability factors

3.3 Step three: Identifying loss elements

a) Prelisting of impacts (based on literature review and historical data).

The findings of the content analysis shows, loss elements considered in past studies are under social, economic and environmental loss categories. However, it is revealed that there is divergence among literature in categorizing the losses as socio, economic and environmental. For example, Porter et al. [34] evaluated aspects of social loss regarding community infrastructures, including wastewater treatment facilities, governmental institutions, historical buildings, places of worship, museums, and educational institutions. In contrast, Deniz et al. [32] confine their evaluation to only residential losses as social losses. Carrivick and Tweed [28] considered impacts on residential property values. Meanwhile, Wen et al. [35] addressed social losses under economic loss. Another study considered only the affected population as social loss [2]. The only study that presented complete methodological guidelines to incorporate SIA into FRM, by Aznar-Crespo et al. [8], also did not consider the crucial elements of loss such as health impacts, household impacts, or educational impacts as social losses. On the contrary, various researches have assessed the social impacts of flooding based on an overall assessment [2, 23, 26, 28, 29]. Table 7 highlights that previous works have segregated different loss components into social, economic, and environmental heads.

Although there is a discrepancy in the categorization of impact elements as social, economic and environmental, one thing is evident in the literature on how to define social, economic and environmental losses. Anything which is directly or indirectly related to the population or residents belongs to society. For example, Carrivick and Tweed [28] considered the overall impacts of the floods as societal impacts. However, most studies considered economic impact as monetarily measurable in the short or long term. In contrast, social and environmental impacts [2] seem to be a mixture of quantitative and qualitative. Yu et al. [2] assessed environmental impact semi-quantitatively in such a case. However, the key impact elements that were assessed in past studies as social impact elements are categorized under the following six (six) categories.

1). Household impact: Impact on residential building /housing, and residential property such as furniture, clothes, electronic devices, and domestic appliances [27, 31, 35].

2). Health impact: Loss of life, physical damage/injury- disease outbreak (cholera, malaria), treatment cost, workdays lost due to injury, psychological effect [8, 22, 23, 26, 35].

3). Impact on social well-being: Social unrest and turmoil due to panic, loss of livelihood [8, 22].

4). Impact on Education: Building damage, cleaning cost, missing school days, temporary classroom and reset service cost [23, 35].

5). Infrastructural losses: Damage to public and social infrastructure and service network and post disaster infrastructure outrage can interrupt social wellbeing of impacted areas community [2, 28, 34].

i) Public infrastructures: damage to water infrastructure such as dam, dike, sluice gate losses, damage to road and railway network (damage and traffic disruptions) also causes social impact.

ii) Social Infrastructure: damage to government building, historic building, house of worship, museum, school.

iii) Service network: disruption to irrigation, drainage, electricity, mobile and telephone network.

iv) Cultural Resources: damage to worship places, recreational places, graveyard.

6). Other Impacts: Population Dynamics/ migratory process due to flood, post flood political consequences due to lack of efficiency in management of flood damage [2, 8, 22, 35].

Table 7. Impact elements of flood risk