Analysis of applicability of flood vulnerability index in Pre- Saharan region, a pilot study to assess flood in Southern Morocco

Abstract. Moroccan Pre-Saharan zone is an oasis system, which it is characterised by extreme events, like drought and flood. The flood risks will likely increases in frequency and magnitude due to global and regional climate change. Flood tends to have an important impact on isolated and poor regions such as oasis regions. This paper aims the analysis of applicability of Flood Vulnerability Index (FVI) in pre-Saharan region of Morocco. The FVI, it is a numerical index that reflects the status of a region’s flood vulnerability. It was determined for four components social, economic, physical, and environmental. These components can help to assist to propose strategies for improvement of the holistic system. For this study five sub-catchments were selected: Upper Draa Valley (UDV), Middle Draa Valley (MDV), Tata sub-catchment, Guelmim sub-catchment and Tafilalt subcatchment; and five urban areas, Ouarzazate, Zagora, Tata, Guelmim and Errachidia. A comparative analysis of the results from thus areas allows us to assess the applicability of the FVI. The overall FVI for these areas was determined by the calculating and standardisation of 36 indicators for each sub-catchment scale and 34 for each urban scale.

Climate change causes acceleration in the frequency of extreme events. Human societies have developed in trying to cope by limiting impacts. In this context the IPCC (2012) has developed risk management strategies. According to the IPCC report, the impacts of changes in flood are highly dependent on how climate changes in the future (IPCC 2012). That is happening for droughts as well. In fact, the impact of natural disasters is correlated to the vulnerability of communities in developing countries, as previous socio-economic vulnerabilities may accelerate these disasters, making the recovery very difficult (Vatsa & Krimgold 2000). Thus, the impact of such events increases the poverty (Carter et al. 2007). Historically, flood has damaged properties infrastructure and thousands of populations. In Morocco, floods are the most dangerous natural disasters, as seen in Fig. 1 and Table 1. The number of affected people and lives lost due to floods exceeds any other natural disasters in the past thirty years.
The data related to human and economic losses) from disasters that have occurred between 1980 and 2010 in Morocco, according to UNISDR (UN Office for Disaster Risk Reduction (www.preventionweb.net), can be seen on Table 2). During this period , 78 dams have been built at the national scale. During the last decade, the notion of vulnerability has changed. After IPCC in 2001 hazards such as climate change, defines vulnerability as "the degree to which a system is susceptible to or unable to cope with, adverse effects of climate change, including climate variability and extremes". Connor & Hiroki (2005)

developed a Flood
Vulnerability Index (FVI), which allows for a comparative analysis of flood vulnerability between different River basins. Methodology which let operators to recognize the key causes conscience-stricken for the basin's vulnerability. Vulnerability is expected to happen under certain conditions of exposure, susceptibility and resilience, measuring the extent of harm (Fuchs et al. 2011). The present article will use the following definition of vulnerability specifically related to flooding (Balica et al. 2009): the degree to which a natural or man-made system is susceptible to floods due to exposure, a perturbation, in co-occurrence with its ability (or inability) to Nat. Hazards Earth Syst. Sci. Discuss., doi:10.5194/nhess-2016-96, 2016 Manuscript under review for journal Nat. Hazards Earth Syst. Sci. Published: 11 April 2016 c Author(s) 2016. CC-BY 3.0 License. cope, recover, or basically adapt. Managing risks from floods should be an important component of climate change adaptation. This study focuses on an approach to assess flood vulnerability and discuss the benefits of adaptation options at a city-scale and sub-catchment-scale, using Flood Vulnerability Index (Balica et al. 2009) in pre-Saharan region. The indicators used show the variables affecting the flood vulnerability in the pre-Saharan region. It provides an important tool for decision maker for monitoring and evaluating changes over time. Data was collected from a variety of sources (see Appendices 2), including household surveys, documents, government and ministries.
The data gathered pertained to the particular indicator to be calculated. The FVI is an indicator-based index which reflects the status of a scale's flood vulnerability. This index was determined for four components social, economic, physical, and environmental. As indicated in the title of this article, the paper aims to assess flood vulnerability in Southern Morocco; in oasis basins, by analyzing the applicability of FVI. Five sub-catchments and five urban areas were selected; the results from thus areas allow us to assess the applicability of the FVI.

Study area
Pre-Saharan North Africa constitutes a major indicator of climatic trends in the Mediterranean region; is currently experiencing a rapid climatic deterioration and desertification (RBOSM 2008). This situation makes the region (see Fig. 2) a vulnerable area. In fact, since the middle of the twentieth century, oases have borne increasing demographic and investment pressures resulting in larger water abstraction, soil salinization, loss of surrounding  The study area corresponds to the perimeters of the oasean provinces of Zagora, Ouarzazate, Guelmim, Tata and Errachidia. It is located in part of the Draa Basin (Upper, Middle and low Draa), and of Tafilalet basin. At the economic level of the entire area, agriculture occupies a prominent place in the economy of these provinces; in fact it is one of the main sources of income and occupies the major part of the workforce (EVICC 2011a). Industrial activity is almost non-existent and the tourism activity remains well below the existing potential. These oasis basins are located near the Wadis (temporary rivers) to facilitate the use of water surface. This location near the Wadi beds is important for the mobilization of water, however it causes the exposure of these areas to flood risk (EVICC 2011e). The floods are rare in the basin of Draa (UDV, MDV, Tata sub-catchment and Guelmim Subcatchment) but they are brutal and violent (PACC 2012a).
The study area has experienced several floods, causing considerable socio-economic damages; we will quote the most important in the study area:

Tafilalet
On the 5 th of November 1965, a flood destroyed the Ziz valley (Tafilalet), leaving 25,000 people homeless and accelerating the decision to build the dam Hassan Addakhil (Saidi et al. 2010). In Merzouga, the last important

Guelmim sub-catchment
In the Guelmim sub-catchment, the drainage system is composed by Seyad Wadi, Oum El Achar Wadi, Ourg Wadi and Assaka Wadi. It is therefore subject to the risk of flooding due to overflowing of these Wadis. The main tributaries of the Assaka Wadi (Seyad and Oum Laachar) have been planning for the spreading of flood waters.
Thus, seven thresholds derivation (small dam) concrete, masonry or gabions have been constructed and are used to derivate flow rates of 15 to 30 m 3 /s per small dam, of a total capacity of derivation of 174 m 3 /s (Water and Environment Ministry).
On the 7 th of January 1985, the Province of Guelmim was hit by flooding due to overflowing of the Oum Laachar Wadi, 33mm in Guelmim center and 65 mm in Bouizakarne in 53min, at a flow rate of 1000m 3 /s(EVICC 2011b).
The importance of these events is due to the socio-economical vulnerability of this area. Unfortunately, human and economic damages for these floods are not available.

Tata sub-catchment
Tata province has experienced several floods. History indicates that the floods that overflow Akka River in 1995 is one of the major events (see Table 3) that impacted the zone. The damage is as following: 13 deads, 2 wounded, 4 missing and 350 families homeless; as well as destruction of 655 homes (EVICC 2011b).

Methodology
In this paper, we used and normalized different variables (indicators) for each selected spatial scale (at urban area and sub-catchment), in a numerical index that reflects the status of a region's flood vulnerability (See Table 4).
Data for calculating the FVI (and initially setting the response levels) were collected for five oasis provinces: Guelmim, Tata, Zagora, Ouarzazate and Errachidia to provide some initial testing of the model. These data were obtained from national and regional reports.

Method for scoring: Standardization/normalization
A standardization method was used for adjusting indicator values in a scale from 0 to 1 (See Table 5).The standardized formula of the FVI is as follow (10): The flood vulnerability analysis was done using a detailed evaluation of the four components of flood vulnerability: social, economic, environmental and physical. These components were gathered and calculated to give the overall vulnerability.

Results
After data collection, the flood vulnerability index was calculated for the four flood vulnerability components and for the total FVI. The indicator values are gathered, compiled and standardized for five case studies selected of Moroccan pre-Sahara region, while the total FVI was determined by the calculating it from the 36 indicators of each sub-catchment and 34 for each urban area.

At urban scale of the Moroccan Pre-Sahara
At urban scale, we used the following equations:   Table 3 presented by U in social component. These indicators emphasize clearly that Zagora is very high vulnerable to floods because this city is characterized by widespread poverty, high rates of unemployment and illiteracy. During floods, planning and measures taken in this city are inadequate. As to the Errachidia city, is small vulnerable and Guelmim is very small vulnerable to floods. Regarding the Ouarzazate and Tata cities, are vulnerable to flood.

Economic Component
The value for the FVI ec is near to zero except for the Tata city. The economic component is largely sensitive to the value of storage capacity of the area because the retention capacity improves the resilience of the cities. In fact, Tata city is very high vulnerable to floods, whereas the other cities have very small vulnerability to floods. The high vulnerability of Tata city is due to the low capacity to water storage. The other four case studies present very low values of exposure. In fact, this relative small vulnerability or resilience is due to the relative higher capacity of storage of water. Effectively, the four cities (Guelmim, Zagora, Ouarzazate and Errachidia) take advantages of the following dams (www.water.gov.ma) and small reservoirs (Ouhajou 1996).
The low vulnerability of Tata, Guelmim and Errachidia is due to the followings: low rainfall, low land use and high evaporation/rainfall rate. Comparing these cities with Zagora and Ouarzazate, the environmental vulnerability of Zagora and Ouarzazate to floods is higher than the three other cities. Figure 5 illustrates that Ouarzazate city has a higher environmental vulnerability to floods due to a relative large rainfall amounts and the low percentage of green areas.

Total Flood Vulnerability Index (FVI total)
All the components together give the total value of the flood vulnerability index for each case study (each urban area). Errachidia (0.09) is small vulnerable, while the four other cities (Zagora (0.47), Tata (0.28), Ouarzazate (0.26), and Guelmim (0.25)) are vulnerable to floods. Comparing these four later cities, the total FVI makes Zagora more vulnerable urban area then Tata, Ouarzazate and Guelmim. Flood management leads to decrease the flood impacts of the socio-economical sector in the pre-Saharan region. The traditional management widely observed in developing countries and vulnerable region take account mainly the economic loses than the environmental and social components. As a measure to the recovery after a flooding event, is the flood insurance, this provides compensation for losses caused by the flood. Particularly, in the case studies, the insurance is not included in the flood risks. The second measure is rehabilitation. The post-flood management problems can be pre-planned. In order to achieve this, objective surveys need to be carried covering human casualties and material damage. On the basis of an objective assessment of hazard, economic, social, and environmental factors, the government should impose that the future development projects will be compliant with the local flood vulnerability.

At Sub-catchments scale of the Moroccan Pre-Sahara
The calculating of the FVI at sub-catchment scale in Moroccan Pre-Sahara requires a total of 36 indicators, presented in Table 2  Guelmim sub-catchment in Guelmim province and Errachidia sub-catchments city in Tafilalt or (Errachidia Province), for the 4 components (social, economic, environmental, and physical) and the total FVI.

Social component
Comparing the five sub-catchments, Guelmim (1) is socially the most vulnerable to floods (very high vulnerability).This high vulnerability is due to the high number of rural population, most disabled people, and the non-functional warning system than the others sub-catchments. Regarding the other sub-catchment, the MDV (0.37) and Errachidia (0.17) are vulnerable to floods, but Tata (0.04) and UDV (0.03) have small vulnerability.

Total Flood Vulnerability Index
The components (social, economic, environmental, and physical) together give the total value of the flood

Discussion
The challenges posed by climate change (CC) increase the importance of adaptation in Moroccan pre-Saharan region. Reduced vulnerability and adaptation to CC cannot be achieved by one sector alone, but all sectors that depend directly or indirectly on services provided from this environment. The impacts of these practices include the loss of land and other natural resources (loss of biodiversity and reduced agricultural). Together, these effects cause a deterioration of living conditions and poverty especially in the rural population. Today, CC aggravates these problems. This paper also provides basic management of flood risk and informs decision makers in development and urban planning. At urban scale, the social vulnerability is very high, and government should reduce vulnerability in Zagora and Errachidia, but also reduce economic vulnerability in Tata To increase the socio-economic level of the poorest people, the government must invest in public transport, education (schools), appropriate housing (economical). Reducing social inequalities in flood vulnerability is the right thing to do. Reducing vulnerability also fight existing socio-economic problems. Because, reducing vulnerability is an interdisciplinary problem. It requires that physical, social and economic scientists and engineers work together to take the lead on flood vulnerability issues.
The methodology used in this paper, is based on several indicators for different factors and two geographical scales, focusing on fluvial and urban floods. Various indicators were taken into account to assess flood vulnerability.
The FVI allow to give solutions by identifying the most and the less vulnerable geographical scale in different sectors (economy, social, physical and environment), and to also bring out an easy to use tool which can be applied and used by the non-scientific community. The results of the FVI study allow that increased knowledge of these sectors can help to assess and manage probable floods. In this way, the FVI helps to identify the exact areas of potential vulnerability for the particularity or elements at risk disregarding of the intensity of the flood, which may occur. The FVI approach attempted to accomplish to take in social science knowledge to define the index indicators individually and thus calculate their vulnerability. As a reminder, the limitation of existing work shows that most collected data is descriptive. That is because most data is gathered and stored in a different ways and formats as this in turn can make comparisons difficult. Therefore, data computation and preparation for such assessments helps to derive higher accuracy. The FVI assessment demonstrated that the FVI tool can be applied at arid zone (Moroccan pre-Sahara), and can generate a range of information to help implement infrastructure projects and to identify areas of risk. The FVI study provides insights the natural and social susceptibility to flood for the four dimensions of the social, economic, environmental and physical for the urban scale. The results of the FVI study could be used for planning of new or better protected settlement in the area.

Conclusion
The methodology used in this paper, is based on several indicators for different factors and two geographical scales, focusing on fluvial and urban floods. Various indicators were taken into account to assess flood vulnerability. The Flood vulnerability Index was used on 5 case studies at two scales (sub-catchment scale and area scale). Lot of data was needed to estimate the flood vulnerability indicators for each of the two areas. An accurate assessment of flood vulnerability is difficult, due to the lack of official necessary data.  The FVI is adaptable to different uses in the Moroccan pre-Saharan region.
 This tool allow to identify the risks and the management methods to assess flood vulnerability;  Find out the priority components and sectors of flood vulnerability in order to take urgent measures  The FVI is applicable in sub-catchment and urban area scales in pre-Saharan region.
 Finally, the proposed methodology to calculate a FVI provides an approach to quantify how much floods are affecting, or can affect a sub-catchment or an urban area in pre-Saharan regions.