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Sinkholes in Karst Environments

Copyright © Jelena Calic-Ljubojevic 2002

Presented By:

Hanumanthappa S. R.

II Year M.Tech (SWE)

PG13AEG5109

Seminar II

ContentsIntroduction

Definitions

Karst Topography Feature

Occurrence of Sinkholes

Causes, Types and Effects of Sinkholes

Sinkhole Characteristics

Case studies

Conclusion

References

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.

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.

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

(Encyclopedia Britannica)

What is a karst aquifer?

• A karst aquifer can be defined as any body of rock composed of solublematerial 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

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

Source: Landscape of Karst Region ( Kentucky Geologic Survey )

Karst plain, central Kentucky

Aquifer make-up

Most commonly assumed

Most commonly true

Causes of SinkholesThe 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.

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

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

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.

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.

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.

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

Global distribution of carbonate rocks (mainly limestone)

Source: http://en.wikipedia.org/wiki/Karst#/media/File:Carbonate-outcrops_world.jpg

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.

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.

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??

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.

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.

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.

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.

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

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.

• 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.

General View of the Dam

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.

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

Two of the sinkholes

Development of joints and

solution in Tal-e-zang.

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

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.

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

•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.

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.

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, Sloveniab 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

• 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

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.

Sinkhole characteristics

• To calculate characteristics they converted raster representation ofsinkholes to vectors and the following basic morphometriccharacteristics were extracted and recorded stratified by rank:

• Diameter, width, area, depth, volume, orientation

• The rotating callipers method was used to delineate minimumbounding box for a set of points thus defining a convex polygon of asinkhole;

• The maximum width of a convex polygon was defined as diameterof a sinkhole and minimum width of a convex polygon was definedas width of a sinkhole.

• Volume was calculated as the sum of differences between themaximum elevation within the sinkhole and the elevation of eachcell of a DTM within a sinkhole.

• Orientation was calculated as an azimuth of a line, connecting thetwo farthest points within the sinkhole.

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.

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.

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.

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.

West Virginia Department of Environmental Protection, 2005,

Sinkhole Mitigation Guidance, Division of Water and

Waste Management, Groundwater Protection Program., Pdf.

(http://www.earthmagazine.org/article/sinkholesfloridagrappleswonde

rsnotsodeep)

(http://www.britannica.com/EBchecked/topic/546115/sinkhole)

(http://www.conserveenergyfuture.com/causeseffectsandtypesofsinkh

oles.php)

(http://en.wikipedia.org/wiki/Sinkholewikipedia.com)

(http://www.usgs.gov/blogs/features/usgs_top_story/thescienceofsink

holes)

Thank You!!