Document Type : Research Paper

Authors

1 Associate Professor in Department of Physical Geography, Isfahan University, Isfahan, Iran

2 Ph.D. Candidate of Geomorphology, Isfahan University, Isfahan, Iran

3 Professor of Physical Geography Department, Ilam University

Abstract

Introduction
Mainly containing thin gypsum units, evaporite formations cover 8% of the Earth's surface and 25% of the Earth's continental surface (Ford and Williams, 2007). The term karst refers to a set of geological processes and the phenomena resulting from the dissolution of carbonate rocks. Decomposing the structure of the rocks forms a unique hydrological regime, leading to the development of special landforms (Ministry of Power, TAMAB, 1994). In general, the eight elements needed to develop a karst are: precipitation, relief, lithology, thickness of carbonate layers, carbon, low temperature, pressure, and tectonic rocks (White, 1988). Sinkholes are the enclosed depressions that are known as the characteristic of carbonate and evaporite karst landscapes. In recent years, several genetic classifications have been published for sinkholes (Gutierrez et al., 2008).
Materials and methods
To conduct this research, a 160,000-m2 area of the Gachsaran formation in Maroon plain with a high density of sinkhole was examined and visited. The exact geographical location and specifications of 51 sinkholes were surveyed, and it was found that the sinkholes totally account for 25% of the surveyed area. Table 1 lists the specifications of the sinkholes. Also, in another field visit conducted in this study area, a sub-basin with an area of 6.2 hectares, average slope of 28%, and length of 2301.7 m was selected for the surface runoff sampling during the precipitation, which also included a number of previously surveyed sinkholes. The surface runoff samples taken included the first moment of runoff onset, which began 3 hours and 27 minutes after the start of precipitation. Then, 5:19, 5:45, 8:10, 9, and 9:20 after the start of precipitation, other samples of surface runoff were taken again to monitor the changes in the ions dissolved in the runoff in the spatial and temporal intervals. The minimum height of this sub-basin is 520 m, and its maximum height is 888 m above sea level. Also, in this regard, to estimate the average long-term rainfall of the region from the 20-year rainfall data of the meteorological stations in the study area, the daily rainfall data of the Maroon meteorological station in the vicinity of the study area, 1:100,000 geological map of Behbahan sheet, 1:50,000 topography, and 10-m DEM of the study area were used as the research data.
Results and Discussion
The obtained results showed that a total of 25% of the surveyed area is covered with the surface and visible sinkholes. It should also be noted that the dissolution in the Gachsaran formation is not the only erosion process that is taking place. In addition to the dissolution of gypsum, the marls of this formation are eroded by the surface runoff due to the precipitation and leave the basin as a suspended load, which accelerates the formation of sinkholes. Therefore, it can be stated that the time interval estimated in this study can be shorter, because the effect of the accelerating factor of the suspended load was not calculated, which requires the investigation and study to calculate the suspended load. Directing the runoff by sinkholes to downstream areas is likely to lead to the same expansion of the underground karst and tunnel, which is not visible. Also, it is not clear how many cavities and tunnels formed in the subsurface of this area, but this is not expected to be low based on the obtained results. There are roads, agricultural lands and, more importantly, residential areas on the gypsum zones, at least 25% of which are visible sinkholes, and the subsurface tunnels that are expanding every year at this dissolution rate. In addition to the effective rainfall, the presence of agricultural lands requiring continuous irrigation and intensifying the dissolution rate can lead to surface collapses and expansion of sinkholes, which ultimately threatens the life and financial security of the inhabitants in these areas.
Conclusion
Based on the field observations and the conducted studies, the sinkholes in the stream course have a generally elongated form and often have several ponors. Given that the sinkholes do not retain the aggregated runoff inside the sinkhole and the runoff exits through the same ponors, such diversity in the number of ponors results in a number of sinkholes in the stream course, which are connected together through a subsurface path. Unlike calcareous sinkholes that can direct the runoff current to karst aquifers, water is rapidly saturated due to the high solubility of gypsum. The dissolution is mainly limited to the opening area of the sinkhole, and less runoff finds the opportunity to expand the sinkhole in depth. It should be noted that based on the results, to increase the safety factor and reduce the risk of gypsum dissolution, it is necessary to monitor and study the subsurface area and to examine the subsurface cavities and tunnels that have formed so far. Finally, to reduce the risks of the dissolution rate, some arrangements such as sinkhole risk zoning should be made. This is because the cavities in the gypsum layers with the high dissolution rate can easily expand and prepare the conditions for the sudden collapse so that the whole plain suffers the collapse, incurring human and financial losses.

Keywords

Main Subjects

  • بهنیافر، ابوالفضل. قنبر زاده، هادی. 1394، ژئومورفولوژی کارست.
  • رضایی عارفی، محسن، زنگنه اسدی، محمدعلی، بهنیافر، ابولفضل، جوانبخت، محمد (1398). محاسبه میزان نرخ فرسایش کارستی با استفاده از تکنیک­های تجربی و آزمایشگاهی در حوضه آبریز کلات در شمال شرق ایران، پژوهش­های ژئومورفولوژی کمی، سال هشتم، شماره 3، زمستان 1398 صص 64-79.
  • زمانی، حمزه، حسن پور، جعفر، چشمی، اکبر 1396، پهنه بندی پتانسیل وجود حفرات کارستی و کاربرد آن برای پیشبینی خطر هجوم آب به داخل تونل ناشی از وجود این حفرات برای استان مازندران، چهارمین کنفرانس ملی کاربرد سامانه اطلاعات مکانی GIS در صنعت آب و برق.
  • سازمان زمین شناسی کشور ، نقشه زمین شناسی مقیاس 1:100000 .
  • صفاری، امیر، قنواتی، عزت الله، علیجانی، فرشاد، محمدی، زکیه، (1395)، مروری بر خصوصیات لندفرم­های کارستی در لایه­های گچی، پژوهش­های ژئومورفولوژی کمی، سال چهارم، شماره 4، بهار 1395.
  • طاوسی، نگار، فرخ نیا، اشکان، هوشیاری پور، فرهاد، (1397)، بررسی اثر سازند انحلا پذیر گچساران بر میزان املاح محلول آب مخزن سد پارسیان، همایش بین المللی توسعه پایدار و عمران شهری، 1397، دوره 8.
  • عباس نژاد، احمد، (1389)، تعیین موقعیت احتمالی غارهای پنهان در دشت کرمان – باغین با استفاده از معیارهای هیدروژئوشیمیایی، نشریه زمین شناسی مهندسی، جلد چهارم، شماره 1 بهار و تابتان 1389.
  • عبدالعلیخانی نژاد، طلیعه، منوری، سید مسعود، سیاوشی، مرتضی، زارعی، سعید، (1394). بررسی تحلیل ارزشیابی لندفیل شهری با رویکرد زمین شناسی در سیستم اطلاعات جغرافیایی، فصلنامه علمی پژوهشی زمین شناسی محیط زیست، سال نهم، شماره 32.
  • محمدیان، محمد، لشکری پور، غلامرضا، غفوری، محمد، قبادی، محمد حسین، 1394، انحلال پذیری سنگ­های گچی (ژیپس) سازند گچساران و اثرات زیست محیطی آن در شرق خوزستان، فصلنامه علوم محیطی، دوره سیزدهم، شماره 3.
  • محمودی، امین، امام، سید محمد رضا (1397). مطالعه آزمایشگاهی و ارایه یک رابطه مقدماتی برای انحلال سنگ­های ژیپس و انیدریت، سومین کنفرانس ملی مهندسی ژئوتکنیک ایران، تهران، 1 و 2 آبان 1397.
  • مقصودی، مهران، زمان زاده، سید محمد، یمانی، مجتبی، حاجی زاده، عبدالحسین، 1396، بررسی تکتونیک فعال حوضه آبریز مارون با استفاده از شاخص­های ژئومورفیک، پژوهش­های ژئومورفولوژی کمی، سال ششم، شماره 3.
  • وزارت نیرو )تماب(،- فرهنگ چندزبانه واژ ه های کارست، سازمان تحقیقات منابع آب ( 1373).
  • Cooper, A.H., Gutiérrez, F., 2013, Dealing with gypsum karst problems: hazards, environmental issues, and planning, Treatise on Geomorphology, Academic Press, SanDiego, CA, vol. 6, pp. 451–462.
  • Gutierrez- Elorza, M., Gutierrez- Santolalla, F., 1998, Geomorphology of the Tertiary gypsum formations in the Ebro Depression (Spain), Geoderma, Vol. 87, pp. 1–29.
  • Gutierrez, F., 1996, Gypsum karstification induced subsidence: effects on alluvial systems and derived geohazards (Calatayud Graben, Iberian Range, Spain), Geomorphology, Vol. 16, pp. 277–293.
  • Gutierrez, F., Calaforra, J.M., Cardona, F., Ortı, F., Duran, J.J., Garay, P., 2008a, Geological and environmental implications of evaporite karst in Spain, Environmental Geology, Vol. 53, pp. 951–965.
  • Gutierrez, F., Cooper, A.H., Johnson, K.S., 2008b, Identification, prediction and mitigation of sinkhole hazards in evaporite karst areas, Environmental Geology, Vol.53, pp. 1007–1022.
  • Gutierrez, F., Guerrero, J., Lucha, P., 2008c, A genetic classification of sinkholes illustrated from evaporite paleokarst exposures in Spain, Environmental Geology, Vol. 53, pp. 993–1006.
  • Gutierrez, F., Galve, J.P., Guerrero, J., 2007, The origin, typology, spatialdistribution, and detrimental effects of the sinkholes developed in the alluvialevaporite karst of the Ebro River valley downstream Zaragoza city (NE Spain),Earth Surface Processes and Landforms, Vol.32, pp. 912–928.
  • Gutierrez, F., Galve, J.P., Lucha, P., Bonachea, L., Jorda´, L., Jorda ´, R., 2009,Investigation of a large collapse sinkhole affecting a multi-storey building bymeans of geophysics and the trenching technique (Zaragoza city, NE Spain),Environmental Geology,Vol.58, pp. 1107–1122.
  • Gutierrez, F., Guerrero, J., Lucha, P., 2008c, A genetic classification of sinkholesillustrated from evaporite paleokarst exposures in Spain, Environmental Geology, Vol.53, pp. 993–1006.
  • Gutierrez, F., Ortı´, F., Gutie´rrez-Elorza,M., Perez-Gonzalez, A., Benito, G., Gracia- Prieto, J., Dura´n, J.J., 2001, The stratigraphical record and activity of evaporate dissolution subsidence in Spain, Carbonates and Evaporites, Vol.16, No.1, pp. 46–70.
  • Gutierrez, F., Cooper, A.H., 2013. Surface morphology of gypsum karst,Treatise on Geomorphology, Academic Press, SanDiego, CA, Karst, Geomorphology, Vol. 6, pp. 425-437.
  • Guo, Sh, Yan, CH, Yu, L, Liu, Y, Zhou, Y, Shi, X, 2020. Characteristics, Controlling Factors, and Formation of Shallow Buried Karst in Eastern China: A Case Study in the Wuxi Metro Areas, Jiangsu Province, Environmental and Engineering Geoscience (2020) 26 (2): 257–269.
  • Haibat, A, Choi, J, 2019, Risk Prediction of Sinkhole Occurrence for Different Subsurface Soil Profiles due to Leakage from Underground Sewer and Water Pipelines, Sustainability 2020, 12, 310.
  • Sanna L. Jo De, W. Calaforra, J. Foorti, P. 2015, Long-term erosion rate measurements in gypsum caves of Sorbas (SE Spain) by the Micro-Erosion Meter method, Geomorphology, Volume 228, 1 January 2015, 213-225
  • White, W. B., Geomorphology and Hydrology of karst، oxford university press. Quinlan, j, 1989،Groundwater monitoring in karst terrains, EPA. 600/ x.
  • William, P. & Ford, D.- Karst hydrogeology and geomorphology, 2007, John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex PO19 8SQ, England, 1-578.
  • Klimchouk, Alexander, THE lypology of Gypsum karst according to its geological and geomorphological evolution,1996, lnt. J. Speleol. 25 (3-4).
  • Williams, P., 2004, Dolines. In: Gunn, J. (Ed.), Encyclopedia of Caves and Karst Science, Fitzroy Dearborn, New York, NY, pp. 304–310.
  • White, W.B., 1988. Geomorphology and hydrology of karst terrains. New York: Oxford university press.
  • Chu, H., Xu, G., Yasufuku, N., Yu, Z., Liu, P., & Wang, J. (2017). Risk assessment of water inrush in karst tunnels based on two-class fuzzy comprehensive evaluation method. Arabian Journal of Geosciences10(7), [179]. https://doi.org/10.1007/s12517-017-2957-5
  • Cooper, H, Anthony, M. Saunders, Jonathan, (2002) Road and bridge construction across gypsum karst in England, Engineering Geology 65 (2002) 217–223.
  • Cooper, H, Anthony, (2006), Gypsum dissolution geohazards at Ripon, North Yorkshire, UK, IAEG2006 Field Trip Guide Ripon.