عنوان مقاله [English]
As one of the largest ports in southern Iran,MahshahrPort faces the risk of seawater intrusion from Mahshahr estuary. Mahshahr and Mousa estuary form an 86 kilometerwaterway. Midday mixed tide is dominant throughout this waterway. Moving towards the vertex of the estuary, this dominance of the midday tidebecomes much more evident. Considering an average depth of 38.4 m, midday tidal wave of M2 with an approximate wavelength of 860 km can be reinforced in this waterway. Grounding of boats and otherammunitions in the basin of Mahshahr port (betweenMajidiyeh garrison and the Persian Gulf) was one of the most important issues during the Imposed War.Mahshahrestuary is the only possible way to access the Persian Gulf fromImam Khomeini port and Majidiyehnaval garrison. From a military perspective,Mahshahrestuary has a special feature that can be considered as a strategic factor and used in various types of active and passive defense. In spite of the shallowness of its internal parts,it is considered to be a safe haven for small vesselsin times of crisis and air attacks. Sometimes, it is critical to use these estuaries and their navigable waterways as the main route for transportation of military weapons, medical aid, and rescue services. Crisis managers and urban planners need an appropriate plan based on risk map of the study areato reduce the risk of tidal process. However, zoning tidal process and mapping its risk are not enough by their own: a useful system needs toidentify sensitive and vulnerable pointsto increase the efficiency of tide risk zoning.
Materials & Methods
Seeking to reduce the risk of tidal process,the present study determinesmaximum level of development in areas covered during high tides usingHecgeoras software. In order to achieve the goals, hydrographic data of the substrate was used along with information and statistics received from high accuracy hydrometric stations. This zonesurrounds an area of around 944 hectares. Field visits indicate thatduring tidal process, soil conditions in the study area hampers sending emergency aids using land routes.Considering the conditions and structures inMahshahr estuary and the tide zone in the study area, investigating geology of the study area seems necessary.
Results & Discussion
Considering the soil conditions in the study area, the highest level of soil flooding was observed during high tide. This increasessoil adhesion, affects water intrusion, and hampers sending aids. Critical areas in danger of water intrusion from the estuary (such as Mahshahr gas reservoirs and Majidieh military garrison) were identified in the present study. Moreover, results were investigated and land visits were performed to present accurate and reliable results. Land visits were carried out during 2016-2017 winter and 2017 summer in order to achieve better and more accurate results based on the climatic changes. Investigating the recorded level of water in the study area shows up to 3-metervariation in the water level of Mahshahr estuary. Necessary decisions regardingthe use of different types of vessels, and passive/active defenses can be made in accordance with water level fluctuations and specified times for each water level. During local visits performed for quantitative analysis of results, soil type and its role in passive defense were also discussed.
Field studies and observations in the study area indicated that 1) dominant soil type of the region is a highly adhesive type with a high clay content; 2) during tide time, soil flooding results in increased adhesion of soil and practically hampers movements of ammunition; 3) In summer and winter, water level changes repeatedly and thus, necessary measures shall be considered for military programs in accordance with the time in which water fluctuations occur. Although the depth of water in the study area is significant, it should be noted that Mahshahr estuary finally reaches an urban area, and thus can be used for military actions. In fact, mapping tide zone is a very effective method for reducing the risk of tidal process in coastal areas.