Introducing an Ecient System for Assessing Solutions for Damage Reduction From Dam Construction on Semi-Arid Forest Areas

Background: Today, the environmental damages of dams are enormous and undeniable, and it is very dicult to reduce these losses. However, environmental damages from dam construction projects may be reduced in intensity and scope through remedial proceedings in the realm of engineering and management operations. The aim of this study was to provide a framework for reducing the destructive effects of dam construction in western Iran in the heart of the Oak forests of the Zagros. Methods: To explore policymaking options and provide technical solutions to reduce damages from the dams and restoration the forests in the region, the scenario examination approach was used in a dynamic model due to the complexity of human-forest relationship interaction and the presence of many actors in this realm. In order to conduct this study, the value of forest ecosystem services in the dam reservoir area in the current situation was estimated. The model of forest growth in the region was prepared in the form of a dynamic system model. Then, the proposed scenarios of reducing the damage caused by the construction of the dam and repairing the damaged vegetation were prepared Results and Conclusion: The dynamic model prepared by variations of forest growth over time and the evaluation of the value of forest ecosystem services made it possible to implement predened scenarios in forest management. Four different scenarios were designed to develop policies for reducing damages caused by the dam construction. According to estimations, the largest share of Oak forest ecosystem services has been in wood and soil production. The value of damage to forest resources due to the Dam reservoir was estimated at $ 16237819.4 and Finally, the appropriate scenario (S4) is one in which conservation, restoration and reduction of pressure on forest resources in the region is proposed as the nal solution to reduce the damages to forest resources caused by dam construction and restoration of vegetation. Also, the afforestation in the area is not a suitable option for remediation of vegetation in this area.


Introduction
In developing countries, dam construction has always been considered as an engineering method for supplying irrigation water in farms, storing drinking water, energy production, ood control and other applications ( has a historical background in Iran, with its dry and semi-arid climate, especially in order to prevent water wastage, deal with water shortage crisis, and regulate river water ow (Tajziehchi et al. 2012). There are different views on the dam construction in the world, which have their own pros and cons among the experts.
Although dam construction has many bene ts for human beings, it has also causes damages that have been irreparable in some cases, because in most cases and in practice, dam construction does not take into account environmental considerations or the necessary forecasts to reduce the environmental, Among the effects of dam construction, mentioned in many studies, their effects on the energy and hydrological cycles of the region, changes in river ow, changes in hydrological and geomorphological system of the region, changes in frequency, peak and duration of oods in the region, reduction of river water ow and changing in the riverbed, increased evaporation from the dam water level that causes changes in the chemical properties of water, increased environmental pollution, spread of waterborne diseases, forced migration of residents of surrounding villages, changes in land use from rangeland and forest lands to agricultural lands and factories, disconnection of path roads from existing roads, Additionally, there is no doubt that the presence of vegetation on the surface of the basin is one of the factors that reduce ooding due to the effects it has on the components of the hydrological cycle (Rezaian et al. 2016;Yang et al. 2019). Therefore, the conservation, restoration and creation of vegetation are very important due to their great impacts on increasing the permeability and duration of concentration and control of surface runoff and other services. Deforestation and destruction of vegetation around dams will reduce the penetrability of the soil or increase the drainage capacity of the basin, which in turn will lead to an increase in ood discharge (Qicai 2011;Chen et al. 2015). Therefore, the environmental impact assessment of dam construction should be considered in a comprehensive manner.
In developing countries, it is usually assumed that the economic bene ts of building dams outweigh its costs, thus providing a logical reason for building dams. But this should not be taken as a loophole to ignore its social and cultural, and especially ecological, damages (Beck et al. 2012;Biswas and Tortajada 2001;Wiejaczka et al. 2020). Although in most parts of Iran, dam construction may be economical in some respects, it is not compatible with the sustainable and comprehensive development plan (Moradi et al. 2010;Zare and Kalantari 2018). In the triangle of sustainable development, striking a balance among economic, social and environmental components at any time and place requires spending money obtained from other sectors in the less developed sector. On the other hand, the emphasis is on meeting the needs of the current and future generations. Therefore, the only way to achieve sustainable development is to pay enough attention to all the ecosystems downstream and upstream of the dams (Heydari et al. 2013;McCartney 2009).
Dam construction causes damage to the natural ecosystems and it is not possible to compensate for the damages, but its damages can be reduced (Moradi et al. 2010). When the decision is made on the construction of the dam, an attempt should be made to adopt a policy that minimizes the threat. A wide range of technical and non-technical operations have been proposed to improve the negative effects of dams (McCartney 2009). Given the inevitable damages from dam construction on the surrounding natural resources, especially forests, methods that can provide solutions to reduce or compensate for the damage in the form of applied policies, can be useful to take utmost care and adopt the right policy in order to refrain from any unconsidered actions (Moradi et al. 2010;Loncar et al. 2006). Dam construction and the resulting consequences on forest resources is a complex phenomenon with different aspects, including various stakeholders, many components and parameters involved, and various goals. It includes a variety of ecological, economic, and social variables that have interrelated, complex relationships and interdependencies between their components. Today, the description of interrelations and the evaluation of their effects, especially the environmental and social effects of dam development, has become an important issue that plays a role in the sustainable development of communities and natural resources. Therefore, its inclusion in a systematic and integrated approach to a project based on sustainable development is important (Tundisi et al. 2015).
Based on the systems perspective, the dynamic system approach rst developed by Forrester (1961) is an idea developed by system modeling methods (Forrester 1961). It consists of a series of cause and effect links through which the interaction between the elements of the system is shown (Olabisi 2010;Collins et al. 2013;Purnomo and Mendoza 2011;Hossain et al. 2020). This technique is used as a tool in the analysis and modeling of systems with various aspects, complex, reciprocal and nonlinear relations, and with feedback and delays (Tao et al. 2017;Machado et al. 2015). This model has been used in an interesting way in various scienti c researches to model complex and dynamic natural and social systems such as natural resource system and forest, whose patterns are a function of time and need long-term planning (Collins et  The performance of the dynamics and scenario modeling system and the formulation of management policies and strategies in the forest based on its simulations has been tested in a series of studies with different criteria. In the oldest study, a dynamic system was used to simulate the dynamics of forest development (Bossel 1994). Also, modeling the dynamic system has been performed for forest re management (Collins et  The construction of Liro Dam in the Zagros Mountains, dominated by the ecosystem of unique forests of the Iranian Oak, is under consideration. Damage to the vegetative coverage of the dam will cause a lot of damage to the region's ecosystem if it is not compensated. In this study, the method of determining the amount of damage and the methods of restoration and reducing damage to the vegetation caused by dam construction in the region have been discussed. To conduct this study, rst a dynamic system model was prepared for Oak forests in the region. Then, the value of ecosystem services of the existing vegetation and its changes over time was estimated in the dynamic system model. In the next step, different options for reducing damage and restoring vegetation under different scenarios and their impacts on damage compensation are examined. In the end, the optimal policies were introduced based on the best scenarios. The results of this study have the potential to provide solutions to reduce the adverse environmental impacts of dam construction by planning to restore the vegetation in the area and to prevent the continuation of forest degradation along the dam.

Study area
In this study, the construction of Liro hydroelectric dam on the common border of three provinces of Lorestan, Chaharmahal and Bakhtiari and Khuzestan in the Oak forests of Zagros, western Iran, was investigated. The annual storage capacity of the dam is 500 million cubic meters. With the construction of the Dam in the most pristine areas of the Zagros Oak forests, a vast part of the forests will be destroyed in one of the most inaccessible and natural areas and tens of thousands of trees in the virgin habitats of the endangered species in Zagros will be submerged. The area is located at the longitude of 50°20 to 49°15 E and the latitude of 32°35' to 20°33' N. The region's precipitation regime is predominantly Mediterranean, ranging from 300 to 1,400 millimeters per year. The average temperature in the region is 18 °C and the average annual evaporation is estimated at 1720 mm.
The dominant ecosystem of the region at the dam's wall consists of the Persian Oak forests and at the bed of the forest reservoir, it is riparian. The schematic of the Iranian Oak forests and the river ecosystem adjacent to the dam can be observed in Fig. 1. The Oak forests of the Zagros in the foothills of the Zagros Mountains are classi ed as semi-arid forests, covering an area of about 5 million hectares, or about 40% of Iran's forests. In general, this region has the greatest impact on water supply, soil protection, climate change and socio-economic balance. Currently, these forests have been damaged in many places due to the harvest of wood and livestock grazing and land use changes (Valipour et al. 2014). The Quantitative characteristics of the existing Oak stands in the reservoir area are as follows (Table 1).

Research Method
To conduct this study, rst, the value of Iranian Oak forest ecosystem services was measured/estimated in the current conditions and priced through conventional methods (alternative goods or costs, opportunity cost method, Willingness to pay for participatory, etc.) ( Then, the vegetation growth model of the region's forests was prepared in the form of a stand-scale dynamic system model, so that the value of forest ecosystem services would be estimated over time. In the next step, the proposed scenarios for the reduction of vegetation damage caused by the construction of the Dam were prepared and evaluated in the constructed model. Figure 2 shows the process of this study.
The forest growth model used in this study, which is based on data obtained from existing local study records, was implemented in the Vensim Dss software, which has the following characteristics.
Model type: Whole-stand Simulator environment: Vensim DSS Simulator facilities: coppice forest natural stand growth, afforested high forest stand growth, calculating the value of ecosystem services (wood production, carbon sequestration, oxygen production, soil erosion reduction, habitat, tourism, pest control, dust reduction, socio-economic), the impact of internal and external factors on forest growth Time validity: 60 years Estimation error: 10 To investigate the quantitative accuracy of the model, the thresholds for the characteristics of Iranian Oak forest stands in Zagros habitat, including stand volume, annual growth, basal area, density, etc. were examined and the problems of the initial model were resolved. To investigate the quality of the model, the relationship between the components of the model was examined, so as not to violate the basic assumptions of forest dynamics.
In this study, a standard approach has been used to devise the scenario (Johansen 2018). In short, for devising the scenario, rst the elements and drivers are identi ed, and then, the variants are formed. Scenarios are designed and nally the selected scenarios are introduced. The scenario building process of this study is shown in Fig. 3.
Estimation of the value of forest ecosystem services in the dam reservoir under current conditions The most important of direct services are soil resources, forage production, wood, charcoal, medicinal plants, tannins, syrup, Oak tree extract, Oak fruit for human and livestock feed, thin skin on Oak fruit skin used in medicine. Most of these values indicate the potentials of Oak forests, and more time is needed to commercialize them and their current valuation may not re ect their true value. Therefore, in this study, wood production and available soil values were calculated, which is the most important element for the survival of other indirect values. From among indirect values, carbon sequestration, oxygen production, soil erosion reduction, soil elements preserving, habitat protection, water production, runoff regulation, dust reduction, tourism services, pest reduction and socio-economic bene ts were selected and evaluated ( Table 2).  Based on strengths and weaknesses, these elements can be converted into the 7 elements described in Table 3.  The elements are arranged on a Wilson matrix according to the impact score and certainty about their implementation (Fig. 4). Finally, the appropriate (effective and certain) elements or drivers were introduced, with which the scenario was created. As shown in Fig. 4, elements 1, 2, and 6 are effective and reliable, and were introduced as project drivers. Development or afforestation elements (elements No. 4 and 5) in semi-arid regions are not reliable and are not recommended, because of the weak habitats and limited water resources, and are not effectively cared for in the long-term. On the other hand, in semiarid areas, including the study area, due to the socio-economic problems of forest dwellers, the forest harvestation rate is much higher than forest growth. Therefore, in order to reduce the destruction of existing resources, the elements of restoration and reduction of pressure on resources must be fully implemented (elements No. 2 and 7) to be effective.
In the next step, possible scenarios of drivers and variants were de ned using morphological analysis. The scenarios considered in the morphological analysis method are as shown in Fig. 5. Variant A is related to the non-implementation of the drivers and variant B is the complete implementation of the drivers. A list of possible scenarios is given in the results section (Table 4).

Examining The Scenarios Using The Dynamic Model
The dynamic system model was used to examine the nal scenarios and simulate them over time. The results of simulation using this model show the analysis of the behavior of problem variables over time in order to present policies and decisions. Part of the causal loop diagram of the ow state of the dynamic system is given in Fig. 6. The main parts of the model include coppice forest growth model, afforestation growth model, calculation of forest ecosystem services, evaluation of forest ecosystem services, effect of external degradation factors on forest growth and nally, the effect of damage reduction and vegetation restoration (conservation, restoration, afforestation and reduction of pressure on forest resources).

Results of estimating the value of forest ecosystem services in the dam reservoir under current conditions
According to the calculations in Table 2, in total, the highest shares of ecosystem services in Oak forests are related to wood production (37%), soil available value (35%) and soil nutrient preserving (21%), respectively (Fig. 7). If the dam is built, 640 ha of Oak forests will be submerged. The value of damages incurred to forest resources from the Dam reservoir is given in Table 4.
It should be noted that the calculation of damages caused by the construction of the dam in the riparian forests is a large problem addressed in the main report of on environmental impact assessment of Liro dam and power plant (2019) and does not t in this article. However, due to the importance and value of riparian forests, the amount of damage has been included in Table 4. Based on the above calculations, the value of the lost forest resources due to the dam construction and the proposed roads (excluding the operation of these forest resources in the future) was estimated at about $16,237,819.4. Model simulation, reviewing the scenarios and formulating the desired policies The list of suggested scenarios is given in Table 5. There is complete internal compatibility in all scenarios S1, S2, S3 and S4, because each has completely distinguished drivers.  Figure 8 is a simulation of the stand under current conditions or in S1 scenario. As it turns out, over time, the soil depth and the stand density and the stand volume decrease, so that the soil gradually disappears in 29 years and the trees of the area, in 35 years. So the volume of the stand reduces to zero. Based on the severity of the destruction under current conditions, in the next 50 years, almost all forested lands within the dam area will be converted to other uses, including garden and agricultural lands, roads, settlements, and so on.
As can be seen from Table 4, the current value of a one-hectare stand of Iranian Oak is estimated at $ 24,151.6. Now, if we add the current value of the stand ($ 24,151.6) to its expected annual value in the next 50 years, with the 7% rate (annual net present value or NPV), the total value of the stand will be obtained (Saeed 2009). To compensate for this damage, four scenarios of S1 to S4 have been implemented, and their annual present cumulative values (ACV) are shown in Fig. 10.
As shown in Fig. 10, only scenarios S3 and S4 can compensate for the calculated vegetation damage in the future, and the difference is in the duration of the vegetation restoration. Under S3 and S4 scenarios, the duration of recovering the lost capital of $32,951.67 is estimated at 33 years and 23 years, respectively. This means that if the S4 and S3 scenarios are implemented, at a surface area equivalent to that of the dam reservoir (640 ha), the damage to the destroyed Oak forest caused by the dam construction will be compensated for over a period of 23 and 33 years. It is clear that with increasing surface area in s3 and s4 scenarios, the damage recovery time can be reduced. The domain proposed for the selection of this 640-hectare area is determined under the name of the effective domain of vegetation destruction due to the construction of Liro Dam according to ecological principles in ecosystem and landscape scale, on which the conservation, restoration and reduction of pressure on forest resources must be implemented. In addition to the Iranian Oak forests that submerge in the dam area, 238 hectares of riparian forest will also be destroyed, so that the same amount of riparian forest should also be protected, restored, resource pressures of which should be reduced elsewise.

Discussion
This study aims to determine the optimal solutions to compensate for the damages caused by the construction of the Liro Dam and to achieve the goals of sustainable development through simulating different scenarios within the dynamic system model and calculating ecological and socio-economic values of Iranian Oak forests in semi-arid areas of western Iran.
Based on the combination of the four options of conservation, restoration, development and reduction of pressure on forest resources, four scenarios S1 to S4 were designed. The results of model simulation in the present study showed that the continuation of the current situation (scenario S1) will cause the complete destruction of forest areas and erosion and destruction of soil. Therefore, the value of the forest stand under this scenario decreases over time. In two scenarios of S3 (reduction of pressure on forest resources along with conservation) and S4 (reduction of pressure on forest resources along with conservation and 100% restoration), the destroyed Oak forest will be recovered in 33 and 23 years, respectively. Therefore, the optimal policy should be such that, rst of all, it guarantees the preservation and conservation of existing forests and reduces the pressure on forest resources. Along with these two, efforts should be made to restore and enrich the forest in order to minimize the damage caused by the dam construction to the forests of the region.
Unfortunately, the existing forest lands face changes in their use every year, especially toward agriculture and quality reduction due to grazing and cutting down trees and soil erosion. With the construction of the dam, the largest share of damages is related to wood (biomass), soil and elements lost in the soil, which is due to the destruction of a forest ecosystem and its conversion into a dam reservoir. Compensating damage to the trees and especially lost soils takes a long time or may not be really compensable.
In order to compensate for the lost trees, considering the low fertility of the habitat and the slow growth of trees and compensation for damages in a short time, extensive afforestation (much more than the area of the dam reservoir) is required. However, large-scale afforestation in arid and semi-arid regions has its own problems, which reduces the possibility of its successful implementation. The main reasons for this uncertainty include the lack of adequate land with su cient area and access to su cient water and the high cost of maintaining afforestation. Also, in many cases, especially in developing countries, afforestation is abandoned after a few years. Therefore, afforestation is not a recommended solution to reduce damage to vegetation due to dam construction in this research. But it is possible to maintain the value of existing forest ecosystem services at a lower cost conservation, restoration and reduction of pressure on forest resource, instead of large-scale afforestation. In the case of compensation for lost soil, reversing the use of low-yield agricultural land to forest may be a good way to compensate for lost soil.
The precondition for sustainable development is that the planning, construction and operation of future dams in the future should be part of an integrated management effort that will lead to the conservation of the environment (McCartney 2009). This is especially challenging in a country like Iran, which is facing both a water shortage crisis and has a very small area of renewable natural resources, including forests. However, with some operations, the adverse environmental effects of these projects can be reduced, which is generally in the form of remedial operations and reduction of damages caused by adverse Investigation of spatial-temporal patterns of deforestation and tropical forest destruction in response to the operation of the Tucuruí Dam in the Amazon Basin using remote sensing and GIS and statistical tests over a period of 25 years 1988 to 2013 by Chen et al. (2015) showed that dam construction can cause disturbances on small and large scales in the forest. But the disturbances caused by the relocation and settlement of human communities (due to its conversion into agricultural lands, exploitation and expansion of roads) has played a major role in deforestation. The destruction caused by humans has increased the vulnerability of the forest to disturbances caused by dam construction in water and soil.
The results also showed that forests that were closer to the dam did not necessarily experience further destruction. Such a problem exists in the forests of the Liro Dam reservoir. In fact, deforestation and the associated social problems are complex issues in developing countries, and this complexity of forest management is a serious obstacle to determining optimal management policies (Musi et al. 2017).
Providing a model which is not only comprehensible but also help policymakers address all of these complex problems is itself a challenge. Therefore, in the proposed approaches, the dimensions of the problem and the method of interacting with them to reduce the damages of the dam construction have been clearly considered from the point of view of stakeholders, including local communities. In a political system for sustainable development of forest resources, in addition to considering different perspectives, government mechanisms to support these resources and nance projects must be rede ned. This study emphasizes the role of conservation and reduction of damages in existing forests instead of new afforestation. Attempts have also been made to use the construction of the dam as an opportunity to support and conserve the forests around the dam. In a way, part of the revenue from the sale of water can be spent on the forests around the dam. Finally, with the implementation of scenarios 3 and 4, the possibility of land use change for agricultural development and cutting tree by the regional natives will be limited. Therefore, to solve this problem and to empower local communities under the new conditions, it is better to change the livelihood of forest dwellers, instead of agriculture and animal husbandry, towards forestry and to provide a new opportunity that is brought about along with dam construction, i.e. tourism.
In the end, the fact should be noted that the construction of the dam, in addition to damaging the reservoir, causes a lot of damage to the surrounding environment in different phases and even after operation, which has not been evaluated and calculated. This could con rm that damages to dam reservoirs can only be reduced, and that these damages cannot be compensated.

Conclusion
The construction of dams on rivers causes many changes in the region's ecosystem. In arid and semi-arid area, in addition to increased water loss through evaporation, it also causes more vegetation to be destroyed, mainly due to the creation of a sustainable water resource to further change land use. The damages caused by the dam construction on the coppice Oak forests of the study area were estimated at about $24,151.6 per hectare.
Dynamic modeling system was used in this study as a exible and effective way to simulate different scenarios of vegetative damage reduction. The proposed approach in this study is to "reduce the damage to natural forest resources resulting from the construction of the Liro Dam by emphasizing conservation, restoration and reduction of pressure on forest resources in the region in the long run with the participation of natives and government funds". Through the conservation of existing forests, we may reduce these negative effects and partially restore the destroyed natural landscape surrounding the dam.
The scenarios presented in this study are based only on legal requirements and the scope of applicable solutions in Iran, but they may be possible to be used in other areas with similar climates and forests.
It should be noted that the estimated amount of damage is the only guideline for predicting damages. It is not tradable and compensation does not mean the reproduction of lost resources. Any type of damage can only be compensated by the same commodity. For example, wood with wood and oxygen with oxygen etc. Also, the costs of reducing or restoring the damage will not be necessarily equal to the amount of damage. In this study, to compensate for the damage to the vegetation around the dam, the costs of conservation, restoration and reduction of pressure on the forest resources around the dam for more than 20 years should be taken into account. At last the process used in this study to determine the appropriate solutions to reduce the damaging effects of dam construction can be used for other similar studies because it is exible and it has used new analytical tools for ecological analysis, including scenario building and dynamic modeling.