Sinkholes in karst environments

22 de Apr de 2015

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Sinkholes in karst environments

  1. Welcome Sinkholes in Karst Environments Presented By: Hanumanthappa S. R. II Year M.Tech (SWE) PG13AEG5109 Seminar II
  2. Contents Introduction Definitions Karst Topography Feature Occurrence of Sinkholes Causes, Types and Effects of Sinkholes Sinkhole Characteristics Case studies Conclusion References
  3. Introduction What are sinkholes? A farmer may view them as naturally forming holes that occasionally open up in the fields. Some people see sinkholes as sites for dumping trash. In urban areas, the sudden appearance of a sinkhole is a hazard that can disrupt utility services, hamper transportation, and cause severe damage to nearby structures.
  4. A sinkhole is a subsidence feature. Subsidence is the downward movement of surface material; it involves little or no horizontal movement. Subsidence occurs naturally due to the physical and chemical weathering of certain types of bedrock. Subsidence can also occur as a result of ; • Underground mining, • Excessive pumping of groundwater or • Subsurface erosion due to the failure of existing utility lines. All of these examples of subsidence can produce surface features that appear similar, but not all are naturally occurring. Some are solely the result of human activities.
  5. Why Care? • Protect the planet • 25% of earths water is from karst aquifers • 10-15% of earth is classified as karst • Land usage planning Source: State of Florida Hydrology Department
  6. (Encyclopedia Britannica)
  7. What is a karst aquifer? • A karst aquifer can be defined as any body of rock composed of soluble material through which groundwater flows and dissolves its own pathways. • Floridan Aquifer = karst – Rock is soluble – Lots of rain/recharge to dissolve rock – Springs – Sinkholes – Caves and conduits Indian Springs, Florida
  8. The process of limestone dissolution over a large area results in a distinct landscape that is called karst topography. Karst topography includes features such as sinkholes, surface and closed depressions, and caves. Karst Topography
  9. Source: Landscape of Karst Region ( Kentucky Geologic Survey )
  10. Karst plain, central Kentucky
  11. Aquifer make-up Most commonly assumed Most commonly true
  12. Causes of Sinkholes The ground beneath our feet is not as much of a solid structure as we think it is. • Humans are also responsible for the formation of sinkholes. Activities like drilling, mining, construction or drain pipes, improperly compacted soil after excavation work or even heavy traffic can result in small to large sinkholes. • Water from broken pipe can penetrate through mud and rocks and erode the ground underneath and cause sinkholes. • Sometimes, heavy weight on soft soil can result in collapse of ground, resulting in a sinkhole. • Areas that have a bedrock made of limestone, salt deposits or carbonate rock are most susceptible to erosion and the formation of such holes.
  13. Types of Sinkholes Sinkholes resulted from a variety of mechanisms, but they have been classified into three broad categories: • Solution sinkholes • Cover Collapse sinkhole • Cover Subsidence Sinkhole Source: Causes, Effects and Types of Sinkholes Conserve Energy Future
  14. 1) Solution sinkholes • Most commonly seen in areas that have a very thin cover of soil on the surface, exposing the bedrock below to continual erosion by water. • As the water percolates through the bedrock, it carries away small parts of the rock with it. • As the bedrock erodes, particles collect in the spaces it leaves. Over a period of time, a small depression is formed. It is at this point where the hole forms. • The hole is usually bowl shaped and can be quite large. Sometimes the bedrock may collapse all of a sudden to form such a solution sinkhole and other times it happens over time. 2) Cover Collapse sinkhole • These take place when the bedrock is covered by a deep layer of soil and earth. Once the bedrock begins to get eroded, crack start forming in the rocky areas around it. • When this happens, a number of weak points begin to form in the layers of soil and strata above it. • Finally, it comes to a point when the weak points become a large hole
  15. within the bedrock that cannot support the weight above it. • The cover collapse usually happens in a sudden manner and can create large holes in a matter of minutes. 3) Cover Subsidence Sinkhole • In this case, the hole is formed over a period of time. The bedrock here is covered by soil and materials which are not well knitted together. • Areas that have soil comprising largely of clay or sand often face the occurrence of this hole. • Once the bedrock starts to erode, the clay or sand starts permeating through the cracks and settles into the spaces left behind. • Over time, this creates a cavity on the surface of the soil and not under it.
  16. Effects of Sinkholes • When they are formed on land, they can change the general topography of the area and divert streams of underground water. • If they form suddenly in areas with heavy population, they can cause a lot of damage to human life and property. • Some holes are formed due to the leak in underground storm drains and sewer systems. • When they collapse, the damage can be seen for many miles due to the repairs that become necessary. • They can be dangerous to the foundations of the building. Toxic chemicals beneath the earth can come up and may pollute the groundwater. • Sinkholes occur commonly in Florida as the state has many underground voids and drainage systems carved from the carbonate rocks.
  17. Karst Landscapes • Cockpit karst Arecibo Radio Astronomy Observatory, Puerto Rico Cockpit karst is a form of karst in which the residual hills are chiefly hemispheroidal and surround closed, lobed, depressions known as dolines or "cockpits" each of which is drained to the aquifer by one or more sinkholes.
  18. Case histories of sinkhole occurrence reveal that sinkholes occur only in certain parts of Pennsylvania. By examining these records, learn that sinkholes are found in areas underlain by carbonate bedrock. Large areas of central and eastern Pennsylvania are underlain by this type of bedrock. William E. Kochanov (1999) What is Carbonate Bedrock? Includes limestone, dolomite, and marble. Limestone and dolomite are sedimentary rocks, and marble is a metamorphic rock. Although sinkholes are associated with all of these carbonate rock types. But, limestone will be used as the primary source. Occurrence of Sinkholes
  19. Global distribution of carbonate rocks (mainly limestone) Source:
  20. Bit about Carbonate sediment • Carbonate sediment is commonly found in relatively shallow subtropical and tropical oceans around the world. • Ocean-dwelling organisms such as corals, clams, and algae use the various elements within seawater to form a hard, rigid skeleton composed of the carbonate mineral calcite. • When these organisms die, their skeletons accumulate on the ocean floor as sediment. • Movement of this sediment by wave action and ocean currents breaks the sediment into smaller pieces and transports it from one place to another. • The sediment can be further reduced in size by the action of burrowing and grazing organisms. • The sediment is ingested by these organisms, available nutrients are removed, and the undigested portion of the sediment is returned to the ocean floor.
  21. How Does Carbonate Sediment Become Rock? Unconsolidated sediment needs something to hold the grains together in order for it to become rock. Limestone is the result of carbonate sediment being cemented together, generally by the mineral calcite. This cement can be produced by chemical reactions that take place in the fluids that move through the pore spaces of the sediment after deposition. Cementation is likely to occur when fresh water, as opposed to ocean water, moves through the sediment. How did the limestone get there if it was formed in the ocean? During the earth’s history, the continents and the oceans have changed in shape and location. Shallow seas covered all of Pennsylvania in past geologic time and produced layer upon layer of carbonate sediments. These sediments were lithified (turned to rock), and the layers were later uplifted, tilted, fractured, folded, and twisted by the forces unleashed during the formation of the Appalachian Mountains.
  22. Chemical Composition of Carbonate Bedrock? • The chief constituent of limestone is the mineral calcite. • The chemical composition of calcite is calcium carbonate (CaCO3). The rock dolomite is similar to limestone but has dolomite as the dominant mineral. [CaMg(CO3)2]. • Chemically, limestone is considered a base. A base is the chemical opposite of an acid. • If an acid is added to a base, the two chemicals will counteract one another, until the acid has been neutralized by the limestone. Which is an ACID that reacts with these materials??
  23. What makes rainwater acidic? Carbonic acid is a weak acid and reacts with limestone and dolomite. In fact, it is the main acid that dissolves carbonate bedrock.
  24. Sinkhole Characteristics • They are commonly circular in outline, but they can also be elliptical, linear, or irregular in shape. • A tunnel or throat may be visible within the hole. • If a sinkhole occurs in an urbanized area, utility lines may be exposed. • The size of a sinkhole depends on how much material has been flushed down the drain and on the size of the pipes. • Initially, sinkholes have steep or nearly vertical sidewalls. • Portions of the sidewalls can break off over time and fall into the sinkhole.
  25. Sinkhole Mitigation • Land use • Existing and planned land treatment • Sinkhole drainage area • Dimensions of the sinkhole opening • Safe outlet for diverted surface water • Environmentally safe disposal of sinkhole “clean out” material • Availability and quality of filter material • Sinkholes may be natural conveyances of organic material and nutrients important to cave fauna. • Safety of equipment and operators and laborers during installation West Virginia Department of Environmental Protection, Division of Water and Waste Management, Groundwater Protection Program, 2005 Source Purpose: Mitigation designs serve to allow the filling of sinkholes while maintaining recharge to the aquifer, reducing potential contamination threats to groundwater, and eliminating safety hazards at sinkhole entries.
  26. Vegetated Buffer Area • Installed around the sinkhole to improve runoff water quality by filtration and adsorption of contaminants. • Within the sinkhole drainage area and should begin at the treated sinkhole. • The buffer will be a minimum of 25-feet wide measured from the rim of the sinkhole. • This width should provide filtering for some distance outside the sinkhole because surface water runoff may be temporarily held before reaching the treated sinkhole. • The sinkhole and surrounding buffer area will be fenced. • Livestock will be excluded from the vegetative buffer except when grazing would be beneficial to maintenance of the buffer. • Appropriate erosion and sediment control measures should be used to reduce the amount of sediment entering sinkhole.
  27. Case Study - I THE EFFECT OF SINKHOLES ON LEAKAGE OF WATER FROM THE SARABCHENAR DAM, SOUTHWEST IRAN M. Ahmadipour Geology Department Lorestan University Lorestan, Iran Journal of Environmental Hydrology, Volume 13, Paper 1, January 2005
  28. INTRODUCTION Study Area • The study area is a part of the Zagros folded zone and is situated in the northwest of Lorestan Province, Iran. • The mean annual rainfall is 550 mm.
  29. • The earth dam was constructed in 1997 in order to control floods for the city of Khoramabad (the capital of Lorestan province) and irrigation of the lands of Sarabchenar village. • The height and the total area of the dam and its lake are 15 meters and 22 hectares respectively. • The dam was designed to store 1600000 cubic meters. • But soon after the construction several sinkholes developed along the lake of the dam, and water storage never reached the estimated design level. • Due to the inflow of sediments and mass wasting, the dam is gradually being filled, and at present it is not used for the intended purposes.
  30. General View of the Dam
  31. GEOLOGY OF THE AREA • Asmari-Shahbazan (white limestone) of Oligocene age, Kashkan (reddish conglomerate, marl and sandstone) of Eocene age. • Tal-e-zang (fine grained and fossiliferous limestone) of upper Cretaceous-Paleocene age and Amiran (gray conglomerate with interbedded red sandstone) of upper Cretaceous-Paleocene age • The Tal-e-zang is seen as small mounds in contact with Amiran formation. Amiran formation (conglomerate with inter-bedded sandstone ). The Amiran formation surrounds the study area in the southern part. The highest point is at an elevation of 1700 meters above the sea level.
  32. Sinkholes • At the contact of Amiran and Tal-e-zang (some authors believe it as Tarbur formation) several sinkholes (ponors) with different diameters and a depth of about 2 meters have developed. • The largest sinkhole has an elliptical (saucer) shape with a diameter of 12 meters in the eastern part of the dam. • Solution, jointing and collapse features are seen on the fine grained limestone at the foot of the Amiran Formation
  33. Two of the sinkholes Development of joints and solution in Tal-e-zang.
  34. WATER RESOURCES Runoff, and the Springs which originate from the Amiran Formation and Recharge the dam. The runoff recharges the lake of the dam in the western and the eastern part. The total discharge of the runoff during high rainfall is 20 liters per second. The streams become completely dry during periods of no rainfall. THE PEYAZEH SPRING Peyazeh spring, which is like an artesian spring and emerges at the contact of Amiran and Tal- e-Zang formation. Peyazeh spring
  35. THE SARABDUREH SPRING • Southwest of the dam at a distance of about 18 kilometers • Asmari (limestone) formation The mean annual discharge is 220 l/s. During the rainy season the spring shows turbidity. THE Q SPRING The spring is situated southeast of the dam at a distance of about 28 kilometers and emerges from the marly limestone of lower Cretaceous age.
  36. Uranine Injection In order to trace the effect of leakage from the sinkholes to the springs of Peyazeh (5 kilometers east of the dam), Sarabdoureh (18 kilometers from the dam) and the Q spring (23 kilometers from the dam) • Eight kilograms of uranine was injected in two of the sinkholes after two days of heavy rainfall in October 2004 through a pvc pipe of 4 inches in diameter Location of the sampling points Injection of uranine in the largest sinkhole
  37. •Samples were taken at different hours and analyzed by the Kharad Pajoh Company. •The effect of uranine was observed after 5 hours in the Peyazeh spring and 2 days later in the Q spring. •The average maximum concentration of uranine in the Peyazeh and Q springs were 41 and 12 ppb respectively. •The low concentrations of tracer are the result of dilution due to large quantities of groundwater flow and absorption by clay materials in the sinkholes.
  38. The absorption of Uranine by the sinkholes can be seen as a red spot CONCLUSION •Sinkholes are formed at the contact of the Amiran and the Tal-e-zang formations. •Due to the solubility of the Tal-e-zang and the development of joints and collapse of limestone, sinkholes have been formed. •Sinkholes are the main avenues for water loss from the dam and there is a direct connection between the sinkholes and the Peyazeh spring. •The Q spring is recharged by the Khoramabad river and it is due to this reason that uranine is seen in the spring.
  39. LIDAR PROCESSING FOR DEFINING SINKHOLE CHARACTERISTICS UNDER DENSE FOREST COVER: A CASE STUDY IN THE DINARIC MOUNTAINS Case Study – II M. Kobal a, I. Bertoncelj b, F. Pirotti c, *, L. Kutnar a a Slovenian Forestry Institute, Slovenia b National Institute of Biology, Slovenia- c CIRGEO Interdepartmental Research Center of Geomatics, University of Padova, Italy The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, 2014 ,Volume XL-7, 113-118
  40. • Leskova dolina, is in the Dinaric Mountains of southwest Slovenia (center of area approximately located at Longitude = 14.46°, Latitude = 45.62° in WGS84 datum). • The karst geology on the site is characterized by numerous sinkhole sand limestone outcrops. • Soils are predominantly from limestone parent material. • Mean annual precipitation of 2150 mm and mean temperature is 6.5°C. Lidar dataset • Lidar data was acquired between 400 and 600 m relative flight height using a Euro-copter EC 120B helicopter and a Riegl LM5600 laser scanner using 180 kHz pulse repetition rate (PRR). Study Area
  41. METHOD Sinkhole detection and extraction • Sinkholes were detected using the lidar-derived DTM. • The initial step is based on a water flow simulation process. It is defined by four steps: (i) watershed delineation, (ii) confining of higher rank sinkholes and (iii) extraction of non-karstic sinkholes.
  42. Sinkhole characteristics • To calculate characteristics they converted raster representation of sinkholes to vectors and the following basic morphometric characteristics were extracted and recorded stratified by rank: • Diameter, width, area, depth, volume, orientation • The rotating callipers method was used to delineate minimum bounding box for a set of points thus defining a convex polygon of a sinkhole; • The maximum width of a convex polygon was defined as diameter of a sinkhole and minimum width of a convex polygon was defined as width of a sinkhole. • Volume was calculated as the sum of differences between the maximum elevation within the sinkhole and the elevation of each cell of a DTM within a sinkhole. • Orientation was calculated as an azimuth of a line, connecting the two farthest points within the sinkhole.
  43. RESULTS • A total of 2660 sinkholes were detected within the study area using the lidar-derived DTM with the cell size of 1 × 1 m. • Majority (2095) were 1st rank sinkholes (density: 40.16 km-2), • 473 sinkholes of 2nd rank (density: 9.07 km-2) • 79 sinkholes of 3rd rank (density: 1.52 km-2) • 12 sinkholes of 4th rank (density: 0.25 km-2) • One sinkhole of 5th rank (density: 0.02 km-2). • Mean width and length of sinkholes increased with the sinkhole rank from 26.1 m at 1st rank to 367.6 m at 4th rank, 33.8 m at 1st rank to 576.0 m at 4th rank, respectively. • Maximum depth of sinkhole ranged from 39.2 in 1st rank to 48.4 m in 4th rank, while sinkhole in 5th rank reaching depth of 52.8 m.
  44. Conclusion • Forest-management, the Dinaric fir-beech forests are among the most important production-forests for timber products; their ecological and nature-conservation aspects are also significant. • The mitigation of climate-changes impacts on Dinaric fir-beech forests in this sensitive karst area is also associated with the distribution of sinkholes and other karst terrain characteristics. • In all forest management actions, the distribution, orientation, depth, and shape of sinkholes have to be taken into account.
  45. Seminar Conclusion • Information about sinkholes is pertinent to planning for future land development and for the protection of private and public property. • It also provides a fascinating story for those who are interested in learning more about geologic conditions and earth processes.
  46. References: Ahmadipour, M., 2005, Effect of Sinkholes on Leakage of Water from the Sarabchenar Dam, Southwest Iran, Journal of Environmental Hydrology, 13: 1. Kochanov, W. E., 1999, Sinkholes in Pennsylvania: Pennsylvania Geological Survey, 4th ser., Educational Series 11, p- 33. Kobal, I., Bertoncelj , F., Pirotti , L. Kutnar., 2014, Lidar prcocessing for defining sinkhole characteristics under dense forest cover, The International Archives of the Photogrammetry, Remote Sensing a nd Spatial Information Sciences, 7: 113-118 Chen, J. and Xiang, S., 1991, Land Subsidence (Proceedings of the Fourth International Symposium on Land Subsidence), IAHS Publ. no. 200. Roberto, S. and Ira, D. S., 2002, Development of collapse sinkholes in areas of groundwater discharge, Journal of Hydrology, 264: 1–11. Vincentzo, F., Antonio, F., Mario, P. and Agata, S., 2012, Sinkhole Evolution in the Apulian Karst of Southern Italy: A Case Study, with some considerations on Sinkhole Hazards, Journal of Cave and Karst Studies, 74(2): 137–147.
  47. West Virginia Department of Environmental Protection, 2005, Sinkhole Mitigation Guidance, Division of Water and Waste Management, Groundwater Protection Program., Pdf. ( rsnotsodeep) ( ( oles.php) ( ( holes)
  48. Thank You!!