Keywords

1 Introduction

All human activities such as land use change and fossil fuel burning increase the release of greenhouse gases into the atmosphere, which results in climate change. The main characteristics of climate change are changes in precipitation, increases in average temperature on a global scale (global warming); melting of ice and glaciers inducing rises in the sea level (UNFCCC, 2007). According to The Fourth Assessment Report of the IPCC, over the last century, the average global temperature rose by 0.74 °C and is predicted by 2100 to range from 1.8 °C to as much as 4 °C. During the twentieth century, sea levels rose by 0.17 m and by 2100, they are projected to rise between 0.18 and 0.59 m (IPCC, 2007). There are many negative impacts of climate change, such as water resources for human use will be exhausted because of the ice and glaciers melting in places such as Greenland in recent years (UNEP, 2007). Moreover, the type, frequency, and intensity of extreme events, such as hurricanes, typhoons, heavy precipitation events, floods, and droughts are also expected to rise (Greenough et al., 2001). If the average global temperature were to rise around 2 °C, approximately 59% of population in the world would be exposed to water shortage (Rockstrom et al., 2009).

Vietnam is one of the countries predicted to be most severely affected by climate change owing to its long coastlines, the high concentration of population, and economic activity in coastal areas, as well as a heavy reliance on agriculture, natural resources, and forestry (Adger, 1999). The impacts of climate change such as typhoons, floods, prolonged droughts, and sea level rises would increase risks to properties, livelihoods, and urban infrastructure assets (MONRE, 2012).

Phanrang-Thapcham is the urban coast of the Ninhthuan province, which is often affected by natural disasters and is predicted to be severely affected by climate change in the coming decades. Recently, droughts and depletion of water resources have frequently occurred, which have severely affected agriculture, aquaculture, urban water supply, and the environment. Moreover, the frequent heavy rains and floods have greatly damaged the urban area and its surroundings. Salinity intrusion, bank erosion, and coastal erosion are also severe impacts in these areas. All consequences have a negative effect on urban development (NinhThuan Provincial People Committee [NinhThuan PPC], 2012).

Vulnerability is a concept to describe a weakness in a system; its susceptibility to physical harm or damage. This concept is used across multiple disciplines, which are often place- or sector-specific. Many literature reviews on climate change have assessed these definitions of vulnerability (Ribot, 1995). The most common use is that the exposure and sensitivity to a hazard and the capacity to adjust to the hazard impacts are essential parts of the vulnerability (Brooks, Adger, & Kelly, 2005). From a social perspective, vulnerability can be considered as the exposure of people to livelihood stress caused by impacts of climate extremes or environmental change (Kelly & Adger, 2004). As such, the vulnerability can be a combination of social factors and environmental risk (Adger, 2006). The vulnerability of climate change is known as a function of biophysical and socio-economic factors (O’Brien, Eriksen, Nygaard, & Schjolden, 2007). Vulnerability is also an equation of the character, magnitude, rate of climate variation to which a system is exposed, sensitivity, and capacity to adjust to the impacts of climate change (McCarthy, Canziani, Leary, Dokken, & White, 2001). Vulnerability to climate change is also defined as the degree to which a system is susceptible to and unable to cope with the negative impacts of climate change, including climate variability and extremes (Adger et al., 2007). The definition of the IPCC is criticized for being too vague and the resulting difficulty in making it operational (Hinkel, 2011). But the definition could be considered as an integrative concept that can link the social and biophysical dimensions of environmental change (Turner et al., 2003).

The general objective of this research study is to calculate the vulnerability index of urban development to climate change, to discover which urban assets are vulnerable, and to classify the major risks concerning resource stress, growth pressure, and management ability. The results of the vulnerability index computed from these basic components should provide the administrators with an estimation of the prevailing situation, modify current policies, and implement mitigation and adaptation measures for sustainable management of water resources in the study region (Figs. 53.1 and 53.2).

Fig. 53.1
figure 1

Map of Phan Rang-Thap Cham city and surroundings

Full size image
Fig. 53.2
figure 2

Framework for vulnerability assessment (IPCC, 2007)

Full size image

2 Methodology

Vulnerability is the degree to which a system is susceptible to the adverse effects of climate change, including climate variability and extreme events. Vulnerability is a function of the character, magnitude, and rate of climate change and variation to which a system is exposed, its sensitivity, and its adaptive capacity.

$$ \mathrm{V}=\mathrm{f}\;\left(\mathrm{E},\mathrm{S},\mathrm{AC}\right) $$

Of which:

  • Exposure (E): the extent to which a system is exposed to the climate change. E depends on the threats (threat intensity, frequency, duration) and location of the system with respect to the threat (how far between the system and the threat).

  • Sensitivity (S): the degree to which exposure to a threat arising from climate change will negatively affect the operation of the system. S may be influenced by the integrity of assets under threats and related factors.

  • Adaptive capacity (AC): a measure of the potential, ability, or opportunities available to decrease exposure or sensitivity of a system to a climate-induced stress.

2.1 Set up Indicator Set

According to IPCC, vulnerability index is a function of E, S, and AC (IPCC, 2007). To calculate these primary indicators, a set of secondary indicators should be constructed. In this study, the set of secondary indicators are made based on the characteristics of natural resources—environmental, socio-economic, data availability of the study area, as well as the expert consultation results. The set of indicators E, S, and AC are described in detail in Table 53.1.

Table 53.1 The indicator set of exposure (E), sensitivity (S), and adaptive capacity (AC)
Full size table

2.2 Determine Vulnerability Index

2.2.1 Determine Indicators (E), (S), and (AC)

Indicators (E), (S), and (AC) were three main elements to determine vulnerability index. These indicators were calculated in both RCP 4.5 and RCP 8.5 in 2030 and estimated according to the methodology and equations in Table 53.2.

Table 53.2 Determine indicators of (E), (S), and (AC)
Full size table

The value of indicators is classified into five categories as below:

Value

0.0–0.2

0.2–0.4

0.4–0.6

0.6–0.8

0.8–1.0

Categories

Very low

Low

Average

High

Very high

2.2.2 Determine Vulnerability Indices

As shown in Fig. 53.1, the potential impact is calculated from (E) and (S), based on the assessment matrices in Tables 53.3 and 53.4. As Fig. 53.2, after (E) and (S) are calculated from Tables 53.1 and 53.2, the potential impact is combined between (E) and (S), based on the follow assessment matrix.

Table 53.3 The assessment matrix of (I)
Full size table
Table 53.4 The assessment matrix of (AC)
Full size table

Vulnerability (V) is calculated based on the Potential Impact (I) and Adaptive Capacity (AC) (V = I × AC).

2.3 Climate Change Scenarios

Vulnerable indices are an important element to develop the adaptive plan to climate change. Therefore, the vulnerable indices calculated should cover both average and severe climate change impacts in the short future. It is the reason the RCP 4.5 and RCP 8.5 scenarios in 2030 are chosen.

3 Results

3.1 Vulnerability Indices under the Baseline Scenario

The results of the vulnerability assessment points out that the vulnerability of several communes is average (15/32 ward/commune). Only three communes, including Phuoc Dan, An Hai, and Phuoc Hai, have high vulnerability because these communes have high exposure and low adaptation. Low vulnerability is identified in communes along the Dinh River owing to low exposure and high adaptation. These communes are located in the urban center (Table 53.5 and Fig. 53.3).

Table 53.5 The vulnerable index of each ward/commune under the baseline scenario
Full size table
Fig. 53.3
figure 3

The vulnerability index map under the baseline

Full size image

3.2 Vulnerability Indices under the RCP 4.5 Scenario in 2030

In 2030, the vulnerable index of most communes shows an upward trend. There are five communes and one town with a high vulnerability index, Nhon Son, Phuoc Thuan, Phuoc Huu, Phuoc Hai, Phuoc Dan, and An Hai communes, whereas most in the urban areas suffer only a low to average index. This can be explained by the fact that the urban area has the lowest to average impact level and the highest adaptation compared with other areas (Table 53.6 and Fig. 53.4).

Table 53.6 The vulnerability index of each ward/commune under the RCP 4.5 scenario
Full size table
Fig. 53.4
figure 4

The vulnerability index map under the RCP 4.5

Full size image

3.3 Vulnerability Indices under the RCP 8.5 Scenario in 2030

Vulnerability in the RCP 8.5 scenario tends to be higher than in the RCP 4.5. Two communes (Phuoc Dan and An Hai) have a very high level of vulnerability and five communes reached high vulnerability (Nhon Son, Phuoc Thuan, Phuoc Huu, Phuoc Hai, and Phuoc Nam). The vulnerability of the urban wards is ranges from a low to an average level. Unlike the RCP 4.5 scenario, the vulnerability in some areas is higher than the level in the RCP 8.5 scenario. In detail, the vulnerability index of Phuoc Dan town and An Hai communes rise from a high to a very high level and Phuoc Nam commune will go from a medium to a high level (Table 53.7 and Fig. 53.5).

Table 53.7 The vulnerability index of each ward/commune under the RCP 8.5 scenario
Full size table
Fig. 53.5
figure 5

The vulnerability index map under the RCP 8.5

Full size image

4 Discussion and Conclusions

4.1 Discussion

Owing to the steep topography upstream, flooding downstream happens quickly (about 4–5 h). The flood risk map (Fig. 53.6) shows that the flooding occurs almost in the urban area, mainly along the banks of the Dinh river. The districts of Ninh Hai, Ninh Son, Thuan Nam, and PR-TC (Phan Rang-Thap Cham), especially Ninh Phuoc district, are the areas that are often severely flooded (accounting for nearly 50% of the district area). The areas with a high flooding risk are mainly located in Nhon Son (Ninh Son District); Phuoc Vinh; the neighboring areas of Phuoc Hau, Phuoc Huu, and Phuoc Thai; and Phuoc Dan and An Hai of Ninh Phuoc district. The urban area is not severely affected because of the surrounding banks, but if extreme flooding occurs upstream, the urban area is affected more severely than other surrounding areas.

Fig. 53.6
figure 6

The map of flooding risk

Full size image

The exposure assessment shows that the high exposure occurs in Phuoc Dan, Phuoc Hai, and An Hai communes (Ninh Phuoc district), Bao An and Thanh Hai ward (the urban area). Other communes and wards of the urban area have different exposure levels, from very low to low.

The sensitivity assessment indicates that the sensitivity varies from low to high. In particular, My Son (Ninh Son) and Phuoc Ninh (Thuan Nam) are highly sensitive. The urban are has low sensitivity to the flood risk. The other communes in the flood-affected area have an average level.

In contrast to the sensitivity, the adaptive capacity of most wards of the urban area is high, except for Dong Hai, My Dong, and My Binh wards (average level), located near the coastal areas. The adaptive capacity is low in communes located in the surrounding areas.

Based on the indicators of exposure, sensitivity, and adaptation of ward/commune in the urban and surrounding areas, the vulnerability of several communes is average (15/32 ward/commune). Only three communes, namely, Phuoc Dan, An Hai, and Phuoc Hai, have a high vulnerability because these communes have high exposure and low adaptation. The low vulnerability is identified in communes along the Dinh River owing to their low exposure and high adaptation. These communes are located in the urban center.

Throughout the time to 2030, the climate change scenarios in Ninhthuan show that extreme weather events happen frequently and intensely. Therefore, the exposure and sensitivity indicators will be higher, leading to high vulnerability. The highly vulnerable areas are almost located in the surrounding areas, especially along the southern bank of the Dinh River, in the areas near the coast, etc., owing to high flooding and low adaptive capacity.

4.2 Conclusions

Recently, extreme weather events such as drought, water depletion, and floods have negatively impacted the Phan Rang-Thap Cham urban area. Therefore, the vulnerability of this area is very high. Throughout time, the vulnerability tends to be higher from the baseline to the RCP 8.5 scenarios. If in the baseline scenarios, there are only three communes with high vulnerability, then in the RCP 8.5, there are two communes with very high vulnerability and five communes with high vulnerability. Generally, approximately 10% of the area has very high vulnerability, 15% of the area has high vulnerability, mostly in the surrounding areas. Thirty percent have low vulnerability, and located mainly in the urban center. The remaining have average vulnerability, and are located near the urban area or are part of the urban area. One of the reasons why the urban area has low vulnerability is because it has high adaptive capacity, although the exposure is almost the same as that of other areas.