- Determination of Design Wave height in Chabahar
Iranian southern coastline bordering the Oman Sea frequently encounters unusual and incidental tropical storms which are capable of generating large waves in this region. In most areas along the coastline, particularity in central and eastern parts, the waves created by tropical storms dominate the coastline because their height is greater than those generated by other atmospheric phenomena such as seasonal west south or east north winds. Most recently, Gonu storm hit the Oman Sea and caused high waves in the Iranian coastlines. It was blowing in an unusual direction and ran a greater distance compared to those common in the region. It recorded waves with elevations of 4 m within Chabahar waters. The Baird and JWRC experts take the view that the height of the significant wave provided in the previous studies has been measured on the basis of a set of simple experimental relations generally applied for the measurement of cyclone speed, central pressure and maximum radius of the wind speed. These relations are not reliable in the main and are no longer used for the analysis of cyclones. Additionally, a number of parameters used in those studies do not match with the today’s knowledge regarding the structure of the cyclones. In this project, a thorough and precise study has been carried out in respect of waves condition resulting from the tropical storms in Oman Sea as a part of an overall development of waves climates in Iranian southern coastlines involving:
- Statistical analysis of historical cyclones derived from various sources ·
- Review of previous studies conducted on tropical storms in the region ·
- Numerical modeling of waves generated by the notable historical storms including Gonu in 2007.
- Numerical modeling of waves created by the tropical cyclones using the Monte Carlo method.
- limit analysis of maximum wave height
Findings of the modeling and analysis performed in the framework of the project could be summarized as below:
Majority of historical storms have occurred in the south east part of the country within 500-1000 km off the coast. Since the waves generated by the cyclone diminish in size as they get far from the direction line of the cyclone, they are found smaller in size along the offshore areas. - Gonu storm having occurred in 1-7 June 2007 is the severest tropical storm recorded in the Arab Sea waters. Entering the Oman Sea, Gonu created waves with elevations of 10 m. Mathematical modeling of this occurrence was performed in this study the results of which well match with the measurements made in respect of the waves generated during the storm.
- Historical data associated with the tropical cyclones (before 1945) confirms the occurrence of numerous cyclones in the Oman Sea affecting Iranian coasts particularly in late 1800s and early 1900s. Relatively little is known about the accuracy of these data. However, Gonu storm is indicative of the fact that the occurrence of these cyclones was quite possible.
- Due to a scarcity of the historical data regarding cyclones, a set
of numerical modeling was conducted using the Monte Carlo method. In
this process, 200 artificial storms were simulated by making random
changes on the historical storm occurred after 1977.
In general, determination of the design wave height along the Iranian coastlines in Oman Sea is heavily dependent on a degree of risk envisaged in the study as well as the reliability of the historical storms data. - If the cyclone direction data in late 1800s and early 1900s are taken reliable, larger size of design wave height appears to be reasonably potential.
Storm direction for the Gono cyclone
Wave index height balance curves
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To avoid financial damages and loss of lives in the event of any such occurrence as Gonu cyclone.
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To identify the best network for buoy deployment in Iranian waters for the measurement of marine parameters.
In addition to the achievements stated above which are greatly interlinked to the fundamental projects defined by the PSO and given the wide-scale programs for the measurement of the marine parameters such as: waves conditions, marine currents, suspended and bed sediments and also studies designed as to the geomorphology and coastline changes, the project outputs will provide a reliable source for the use by the coast experts for optimization of design in the project area. It is worth noting that a key factor for formulating an optimum and cost-effective project is definition of the design parameters as reliable and precise as practicable. Due to a lack of measurement data of these parameters in Iranian waters as well as a lack of reliable modeling, great majority of designs made by the consultants perforce have been on the basis of unreliable parameters data having rendered, in most cases, to non-economic projects with gross errors. Furthermore, misunderstandings over the morphologic changes trends and coastline changes as a consequence of marine structures are observed. This has no doubt led to increased operational costs and decreased efficiency of the projects. Problems of sedimentation in majority of the Iranian ports and infliction of sedimentation operational costs are few examples. Implementation of the present project, due to the measurements and studies anticipated, will form a reliable basis to overcome relevant problems of the ports covered by the project and will serve as a valuable guide for future designs.
