Prepared in cooperation with the Polish Geological Institute

Evaluation of Landslide Monitoring in the 

Polish Carpathians

Brian D. Collins, Rex L. Baum, Teresa Mrozek, Piotr Nescieruk, Zbigniew Perski, 

Wojciech Rączkowski, and Marek Graniczny

Open File Report 2011-1001

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia 2011 

For more information on the USGS—the Federal source for science about the Earth,

its natural and living resources, natural hazards, and the environment:

World Wide Web: http://www.usgs.gov

Telephone: 1–888–ASK–USGS

Suggested citation:

Collins, B.D., Baum, R.L., Mrozek, Teresa, Nescieruk, Piotr, Perski, Zbigniew, 

Rączkowski, Wojciech, and Graniczny, Marek, 2011, Evaluation of landslide 

monitoring in the Polish Carpathians: U.S. Geological Survey Open-File Report, 

2011-1001, 30 p. [http://pubs.usgs.gov/of/2011/1001/].

Any use of trade, product, or firm names is for descriptive purposes only and does 

not imply endorsement by the U.S. Government.

Although this report is in the public domain, permission must be secured from the 

individual copyright owners to reproduce any copyrighted material contained within 

this report.
iii

Contents

Executive Summary............................................................................................. iv

Introduction ...........................................................................................................1

Background...........................................................................................................3

Regional Setting and General Overview of Landsliding in the Polish 

Carpathians................................................................................................3

Climate and Storm Events of Spring and Summer 2010 in Southern Poland ....4

Monitoring Strategies............................................................................................4

Performance Monitoring.....................................................................................5

Real-Time Warning System Monitoring .............................................................5

Near-Real-Time Monitoring for Early Warning ...................................................6

Research Monitoring..........................................................................................7

Evaluation of Existing PGI Monitoring Locations and Recently Reactivated 

Landslides.....................................................................................................7

Just Landslide....................................................................................................7

Hańczowa Landslide..........................................................................................8

Szymbark (Huciska and Zapadle) Landslides..................................................10

Kłodne Landslide .............................................................................................11

Siercza Landslide.............................................................................................12

Łaśnica Landslide ............................................................................................14

Łazki Landslide ................................................................................................15

Siedloki Landslide............................................................................................16

Example of a Near-Real-Time Warning System .................................................19

Managing Public Perceptions about Real-Time Landslide Monitoring and Early 

Warning ......................................................................................................24

Potential Research Questions To Be Answered By Monitoring ..........................25

Conclusions ........................................................................................................26

Acknowledgments...............................................................................................26

References Cited ................................................................................................27

Figures 

Figure 1. Location map of Poland showing landslide sites visited in September 

2010. ...............................................................................................................2

Figure 2. Sketch map, cross section, and details, of hypothetical landslide.......20

Tables

Table 1. Summary monitoring suggestions for landslide sites visited in Poland, 

September 2010............................................................................................18

Table 2. Equipment for near-real-time monitoring of hypothetical landslide. ......22

Appendix

Appendix A. General Considerations for Real-Time and Near-Real-Time 

Monitoring......................................................................................................29
iv

Executive Summary 

In response to the June 15, 2010 request from the Polish Geological Institute 

(PGI) to the U.S. Geological Survey (USGS) for assistance and advice regarding realtime landslide monitoring, landslide specialists from the USGS Landslide Hazard 

Program visited PGI headquarters and field sites in September 2010. During our visit we 

became familiar with characteristics of landslides in the Polish Carpathians, reviewed 

PGI monitoring techniques, and assessed needs for monitoring at recently activated 

landslides. 

Visits to several landslides that are monitored by PGI (the Just, Hańczowa, 

Szymbark, Siercza and Łasńica landslides) revealed that current data collection (monthly 

GPS and inclinometer surveys, hourly piezometers readings) is generally sufficient for 

collecting basic information about landslide displacement, depth, and groundwater 

conditions. Large landslides are typically hydrologically complex, and we would expect 

such complexity in Carpathian landslides, given the alternating shale and sandstone 

stratigraphy and complex geologic structures of the flysch bedrock. Consequently 

groundwater observations could be improved by installing several piezometers that 

sample the basal shear zone of each landslide being monitored by PGI. These could be 

supplemented by additional piezometers at shallower depths to help clarify general flow 

directions and hydraulic gradients. Remedial works at Hańczowa make the landslide 

unsuitable for monitoring as part of an early warning network. Monitoring there should 

focus on continued performance of the remedial works. 

Our suggestions for new monitoring at recently activated landslides are 

summarized in table 1. Displacement monitoring using extensometers and (or) GPS is a 

high priority at Kłodne, Łaśnica, Łazki, and Siedloki. Geomorphologic mapping of active 

surface features (scarps, cracks, shear zones, folds, and thrusts) in sufficient detail to 

reveal the kinematics of each landslide would greatly help in planning subsurface 

exploration and monitoring. Mapping should take advantage of existing and future 

airborne lidar data sets of specific areas, where available. Borehole inclinometers and 

piezometers would complete the basic monitoring package for these landslides. The 

landslide at Kłodne may be well suited for more detailed monitoring for landslide process 

research, although research opportunities exist at the other landslides as well. The 

landslide near Siedloki may be a good candidate for terrestrial laser scanning (TLS).

Tandem streamflow gages upstream and downstream from the Siedloki landslide, or laser 

distance meters to monitor advancement of the toe, may be needed to provide warning of 

stream blockage of Potok Milowski. A real-time warning system specifically for the 

Łazki landslide might be considered due to potential concerns about catastrophic 

movement into Międzybrodzie Reservoir.

Challenges associated with the establishment of a complete real-time monitoring 

and early warning system are far greater than just the technical and logistical aspects of 

installing remote monitoring systems at a large number of landslides. Long-term 

maintenance of a landslide monitoring network will involve considerable effort and 

expense as sensors break-down from exposure to weather, landslide movement, and harsh 

underground environmental conditions. 

Once PGI’s planned pilot network of 10-20 monitored landslides is operating, a 

period of observation and analysis will be needed to establish appropriate alert levels and 
v

criteria for issuing alerts and warnings. Simultaneously, discussions with authorities will 

be needed to develop action plans for responding to landslide notifications and (or) 

warnings. Public resistance to landslide warnings and mandated evacuations may be high 

given the low historical incidence of fatalities and injuries resulting from Carpathian 

landslides and the small potential for warnings to reduce landslide damage to homes and 

land. Careful weighing of purpose, advantages, and costs of a large-scale monitoring and 

early warning program is needed early in the planning process and should be revisited 

regularly throughout pilot and final implementation. 

In this report, we present a generic plan for monitoring of a hypothetical 

Carpathian landslide that illustrates how our suggestions for each of the specific 

landslides could be implemented. The plan includes basic pore pressure, displacement, 

and weather monitoring, along with supplemental monitoring for special conditions at 

specific landslides. Table 2 summarizes the overall approach and basic equipment and 

software requirements.
1

Evaluation of Landslide Monitoring in the 

Polish Carpathians

Brian D. Collins1, Rex L. Baum2, Teresa Mrozek3, Piotr Nescieruk3, Zbigniew 

Perski3, Wojciech Rączkowski3, and Marek Graniczny4 

1

U.S. Geological Survey, Geology and Geophysics Science Center, Menlo Park, California, USA

2

U.S. Geological Survey, Geological Hazards Science Center, Golden, Colorado, USA

3

Polish Geological Institute, Carpathian Branch, Kraków, Poland

4

Polish Geological Institute–National Research Institute, Warsaw, Poland

Introduction

During late spring 2010, in the course of discussions about potential collaboration 

between the Polish Geological Institute (PGI) and the U.S. Geological Survey (USGS), 

widespread activation of hundreds of landslides occurred in the Carpathian Mountains of 

southern Poland. This resulted in an urgent request, dated June 15, 2010, from PGI for 

USGS assistance regarding real-time landslide monitoring and early warning systems. 

The request called for advice on automated data-acquisition equipment, instrumentation, 

and software for real-time monitoring of individual landslides and for a visit by USGS 

landslide experts to review methods of monitoring currently used by PGI. In response to 

this request, copies of two USGS reports on landslide-monitoring techniques were sent 

immediately (Baum and others, 2008; Reid and others, 2008), and in September 2010 a 

team of two USGS landslide specialists, Rex Baum and Brian Collins, were sent to meet 

with PGI officials. The USGS specialists visited examples of monitored and recently 

activated landslides for the purpose of developing suggestions about monitoring and 

discussing potential cooperation between the two agencies. 

Meetings between USGS researchers (Baum and Collins) and PGI officials (Chief 

Director Jerzy Nawrocki, Wojciech Brochwicz-Lewiński, Dariusz Grabowski, Marcin 

Kułak, and Teresa Mrozek) took place at PGI headquarters in Warsaw, Poland on 

September 9, 2010. Field visits with PGI geologists (Teresa Mrozek, Piotr Nescieruk, 

Wojciech Rączkowski and Zbigniew Perski) took place over four days between 

September 10-14, 2010. At the meeting in Warsaw, PGI briefed the USGS about ongoing 

development of a detailed landslide database and hazard-zone maps (based on expert 

opinion), as well as plans for monitoring of up to 100 landslides. The pilot phase of 

landslide monitoring is expected to involve between 10 and 20 landslides. USGS

understood from the briefing that PGI places high priority on selecting methods for (1) 

objective, probabilistic landslide-hazard zonation and (2) real-time landslide monitoring 

to address a directive from the Polish Ministry of Environment to provide information 

about when landslide acceleration or reactivation can be expected. USGS researchers

briefed PGI officials about landslide-monitoring techniques and landslide-hazard 
2

Figure 1. Location map of Poland showing landslide sites visited in September 

2010.

zonation methodologies developed by the USGS. During field investigations we visited 

eight landslides in detail (fig. 1) and stopped briefly at several others.

The remainder of this report provides brief descriptions of the landslides that we 

visited, our assessments of current monitoring at each site, and suggestions for further 

development of existing monitoring systems or development of new monitoring systems 

at recently activated landslides. Additional comments are provided about definitions and 

descriptions of four general classes or types of monitoring, a detailed description of a 

monitoring system for a hypothetical landslide in the Carpathian Mountains, some 

comments about the sociological aspects of real-time landslide monitoring and early 

warning, and a list of lessons learned from USGS monitoring experiences. 

Łazki

Kraków

Slovakia

Siedloki

Just

Hańczowa

Szymbark

Kłodne

Siercza

Łaśnica

Poland

Slovakia

Czech 

Republic

Baltic Sea

Kraków

Warsaw

To Warsaw

0 50 100 km N
3

Background 

Regional Setting and General Overview of Landsliding in the Polish 

Carpathians 

Landsliding in Poland is predominantly confined to the southern portion of the 

country in the area of the Polish Flysch Carpathian Mountains. More than 90 percent of 

all landslides occur within this area, which represents only 6 percent of the land area of 

Poland (Wójcik and others, 2006). About 60,000 known landslides have been mapped 

and included in PGI’s database (Marcin Kułak, personal commun., 2010). The area is 

part of the larger Carpathian thrust and fold range that stretches in an arc from Austria 

(the Vienna Basin) in the west, through Slovakia, the Czech Republic, Poland, and 

Ukraine in the north, to Romania (the Iron Gate) and Serbia in the southeast. The 

Carpathians are subdivided into the Western and Eastern Carpathians (the latter also 

called the Southeastern Carpathians) depending, in general, on their respective 

physiography. These are further divided into specific ranges, basins, and plateaus (for 

example, Beskid Niski and Pogórze Wielickie in Poland). Subdivisions along the arcuate 

mountain range of the Outer Carpathians and Inner Carpathians are attributed mainly to 

structural, tectonic, and lithologic differences.

The Polish Outer Carpathians are dominated by Cretaceous to Tertiary 

(Paleogene) flysch deposits consisting of sequential layers of shales and sandstones 

deposited in a deep marine basin during continental mountain building. Younger (late 

Tertiary) sediments sometimes overlie the flysch deposits. The flysch deposits of specific 

sedimentary basins form rock series (successions) where the nappes are thrust over one 

another and also over the Carpathian foredeep. The successions are named after the 

nappes (for example, Magura, Silesian, Sub-Silesian, and Skole Nappes) and reflect 

specific sedimentary conditions of particular basins. In Poland, to simplify a rather 

complicated sedimentary pattern, the flysch deposits are occasionally divided into three 

major categories: (1) normal flysch, consisting of adjacent sandstone and shale beds of 

approximately equal thickness, (2) shale flysch, where shale beds are thicker than 

adjacent sandstone beds, and (3) sandstone flysch, where the opposite holds. Thrusting 

and consequent folding of the greater Carpathians has fractured and folded the majority 

of flysch deposits throughout most of southern Poland. Whereas landsliding along 

(parallel to) shale beds is common, landslides occur in all flysch deposit types and both 

parallel and perpendicular to existing geologic structures. In addition, landsliding in 

younger Miocene clays is also common (Wójcik and others, 2006). 

Historical landsliding in Poland is well documented and investigated. Studies 

show that some landslides can be traced back to environmental changes associated with 

Pleistocene post-glacial warming and Holocene climate swings (Alexandrowicz and 

Alexandrowicz, 1999) and that reactivation of older Holocene landslides has occurred in 

more recent times (Bajgier-Kowalska, 2008). Studies on recent landslides show definitive 

quantitative signals between precipitation, groundwater level and landsliding in several 

areas (Gil and Długosz, 2006; Gil and others, 2009; Zabuski and others, 2009). Finally, 

recent geotechnical studies show that high pore-water pressures are often the trigger for 

deep-seated landslides (Bednarczyk, 2008), suggesting that basal pore water pressure 

measurements might be the best indicators of future landslide movements. 
4

Climate and Storm Events of Spring and Summer 2010 in Southern 

Poland 

Southern Poland has a temperate climate influenced by both Atlantic maritime 

and Eastern European continental conditions. Summer brings warm (average temperature 

21°C), comfortable temperatures, whereas winter brings cold (average temperature 0°C) 

and snow. In general, rainfall is highest in the summer months (June, July, August), but 

can be severe in spring as well. The city of Kraków, located in the central area of 

southern Poland receives approximately 631 mm of rainfall annually (Institute of 

Meteorology and Water Management, 2010). When coupled with snowmelt events, early 

spring rainfall can cause flooding, although rainfall alone has also caused extensive and 

more frequent flooding in the past. 

Southern Poland received heavy snowstorms during the winter of 2009-2010, and 

consequent melting in the spring led to high groundwater conditions and saturated soils. 

In May 2010 a low pressure system developed over Genoa Bay (northern Mediterranean 

Sea). This was followed by another low pressure system affecting Poland that followed a 

more typical meridional track moving from the Balkan Peninsula to Central Europe and 

subsequently, became stationary there. The warm, moist air masses from the low pressure 

systems gliding over colder air from the northwest and orographically lifted by the 

Carpathian Mountains brought about prolonged and intense precipitation, and finally 

flooding, in southern Poland. Daily precipitation exceeded typical monthly levels from 

May 15-17, with reports of 200 mm of rain in 24 hours (Telegraph, 2010). Flooding led 

to several fatalities and levee breaches in central and southern Poland. Landslides 

resulting from high levels of precipitation were distributed across a wide area throughout 

southern Poland. Additional storms in early June (June 1-3) resulted in more than 100 

mm of rainfall (World Meteorological Organization, 2010). This led to continued 

flooding and reactivation and mobilization of both existing and new landslides. Storms in 

August and again in September resulted in additional flooding and reactivation of 

existing landslides and activation of new landslides.

No fatalities due to landsliding were reported from these events, in large part 

because landslide velocities were generally slow (meters per day). As a result, residents 

evacuated either on their own, or were assisted by local authorities and building 

inspectors. Cracking of plaster and brick homes was ubiquitous where structures were 

located within landslide boundaries. Structures typically collapsed completely where 

deformation was severe, usually after meters of displacement. Due to the severe levels of 

damage suffered in many communities, Polish and European Union emergency funds 

became available for repair and reconstruction efforts. During our site visit, we were 

informed that some displaced residents of damaging landslides had already begun to 

relocate in areas away from their damaged homes.

Monitoring Strategies

Landslide monitoring can take various forms which are typically selected with 

specific purposes in mind. For example, in some cases, monitoring may be desired to 

confirm the performance of already built mitigation structures. In other cases, monitoring 

may be required as part of an early warning system. We have defined four categories of 

monitoring to aid in describing and organizing our suggested landslide-monitoring 
5

approaches and equipment at each of the sites investigated: (1) performance monitoring, 

(2) real-time monitoring for warning, (3) near-real-time monitoring for warning, and (4) 

research monitoring. These categories, described below, have been developed based on 

our general discussions with PGI officials in Warsaw, our site-specific evaluations with 

PGI geologists in the field, and our own understanding of and experience with landslidemonitoring systems and their purposes. 

Performance Monitoring 

When mitigation measures have been implemented to either arrest landslide 

movement or protect existing infrastructure, performance monitoring may be desired as a 

means to determine if mitigation structures are acting effectively. In these cases, 

monitoring will typically consist of some form of displacement instrumentation (for 

example, downhole inclinometers, surface tiltmeters, or geodetic-survey measurements).

The purpose of this type of instrumentation is to confirm that deformations are not taking 

place with respect to the mitigation or protected structure. In many cases there may not be 

a need for real-time or near-real-time monitoring because of an assumption that the 

mitigation strategy will act according to design. Thus, monthly or annual measurements 

are typical and may be sufficient. If a high-sampling rate is desired (that is, less than once 

per month), a stand-alone datalogger and batteries/power connection are suggested with 

sufficient capacity to make and store measurements between manual download intervals 

by personnel sent to the field. However, remote-access capability (for example, cell 

phone uplink) may also be integrated. For sampling rates greater than once per month, it 

may be sufficient to send personnel directly to the field to make each measurement, 

depending on travel distance. Regularly scheduled maintenance of instrumentation and 

dataloggers should be implemented, but in general, is not as critical compared with other 

monitoring strategies.

Real-Time Warning System Monitoring 

In cases where lives or infrastructure are threatened directly by landslide motion, 

a real-time monitoring system may be desired. These systems typically use displacementmeasurement instrumentation (for example, inclinometers, tiltmeters, and extensometers), 

but may also consist of surface and subsurface hydrologic-response instrumentation (for 

example, piezometers and streamflow gages), as well as weather instrumentation 

(precipitation, air temperature, barometric pressure). This instrumentation is typically 

used to detect landslide deformation or acceleration, but may also be used to detect if 

hydrologic or meteorologic conditions are sufficient to trigger landslide motion. An 

example of this latter purpose would be measuring landslide basal shear zone pore-water 

pressures in conjunction with an existing deterministic slope stability model to evaluate 

landslide stability (that is, Are pore water pressures sufficient to cause a factor of safety 

less than 1.0?). In this example, a thorough knowledge of the landslide topography, 

geometry, geology, and style of motion are necessary. Typically, instrumentation 

sampling rates are on the order of seconds during peak triggering conditions (for 

example, during heavy precipitation). Systems must, therefore, be capable of detecting a 

rapid event. These systems require installation of one or more dataloggers, radio/cell 

phone/satellite/IP modem uplink capability, and a continuous, dependable power supply. 

Redundant systems of dataloggers, sensors, communications, and power are generally 
6

needed for remote monitoring of potentially hazardous landslides. Additionally, a 

schedule of periodic maintenance should be implemented and strictly followed to ensure 

the functionality of all monitoring-system components. If a component of the system 

fails, repair should be made within 24 hours, if possible and safe to do so. A decision 

matrix should be implemented prior to bringing the system online based on a clear 

understanding of the data and its meaning with regard to slope stability. The decision 

matrix should include a carefully defined list of actions to take at each predefined level of 

hazard. Finally, prior arrangements must be made with local authorities to react rapidly 

(within seconds to at most minutes) and appropriately should the instrumentation indicate 

a hazardous condition. 

Near-Real-Time Monitoring for Early Warning 

A near-real-time warning system is typically desired when incoming data is 

important for understanding current field conditions, but when acting upon these 

conditions immediately is not required. “Early warning”, as used here, indicates data 

collection, transmission, and interpretation capabilities on the order of 10 minutes to 

several hours. As an example, this type of application could be implemented when 

municipal officials would like to know when conditions for landsliding are likely to occur 

so that they can be in a position to either inform or warn residents, or to prepare 

emergency-response equipment and personnel (for example, electrical utility crews).

Here, knowing the exact moment of landsliding is not necessarily required, but being 

prepared for an adverse circumstance is desired, particularly if potential changes in field 

conditions occur slowly (that is, over tens of minutes to hours). Near-real-time warning 

systems can utilize a wide range of instrumentation types, including those for surfaceand subsurface-displacement monitoring, surface- and subsurface-hydrologic monitoring, 

and weather monitoring. Instrumentation sampling rates are typically between 10 minutes 

and several hours in length. Similar to real-time warning system monitoring, a full suite 

of dataloggers, uplink systems, and dependable power supplies are needed, but 

redundancy of components is less critical. In general, instrumentation does not need to be 

maintained as frequently as for real-time systems. With near-real-time systems, if there is 

a problem with any part of the instrumentation installation, it is generally acceptable to be 

able to fix the problem within a 14-day period outside the storm season and within a 48 to 

72-hour period during storm season (depending on the proximity of other monitoring 

stations and how rapidly landslides respond to rainfall). Still, regular (semiannual or 

annual) maintenance should be performed to ensure functionality prior to storm seasons. 

Certain types of instruments, such as tensiometers, may require maintenance on a more 

frequent (quarterly or monthly) basis. Depending on the application, a decision matrix for 

interpreting the various data signals may be necessary. If the goal of the system is to warn 

municipalities that landslide conditions exist, the definition of various condition types 

(for example, “Outlook”, “Watch”, or “Warning”; see Chleborad and others, 2008) must 

be clearly delineated and a means to convey this information must be implemented and 

maintained (for example, contact information for various end users should be regularly 

checked and updated). As in the case of a real-time warning system, clear instructions 

need to be developed concerning actions to be taken by end-users and the general public. 
7

Research Monitoring 

In some cases, monitoring may be desired for the purpose of understanding the 

underlying phenomena that is causing landsliding (Reid and others, 2008). This type of 

monitoring, termed “research monitoring” is usually aimed at collecting data to assist in 

answering a particular scientific question. Although in most cases, data provided by a 

real-time or near-real-time system will be perfectly sufficient for answering research 

questions, there are situations where warning systems are not necessary, and the data can 

be logged without the need for continuous uplink and transmission from a remote 

location. For example, if the kinematics of a particular landslide may assist in explaining 

a general stability or hydrologic concept common to other landslide areas, a single 

landslide may be rigorously instrumented to learn about this behavior. In these cases, 

there may be no imminent danger or societal affect from the landslide, and thus, remote 

data transmission may not be necessary. Rather, all data may be able to be logged on site 

and periodically retrieved. A downside of this type of configuration however, is that if 

instrumentation fails, the cause and timing will not be known until the time of the next 

site visit. Further, any cost savings realized by eliminating a communications link may be 

partially offset by increased travel costs and field time needed to collect data.

Maintenance schedule and repair requirements for research monitoring systems are 

similar to those for near-real-time monitoring systems.

Evaluation of Existing PGI Monitoring Locations and 

Recently Reactivated Landslides

The following site descriptions and suggestions have been prepared based on our 

understanding of each landslide obtained through site visits, discussions with PGI 

geologists, and a review of documents provided by PGI. In the section title for each 

landslide, a suggested level of monitoring (monitoring strategy), as described previously, 

is included. Each site description contains three sections outlining (1) the location, 

setting, and description of recent damage; (2) a general description of landslide 

dimensions and monitoring methods currently used; and (3) an evaluation of existing 

monitoring and suggestions for additional monitoring that could be implemented. A 

summary is provided in table 1, following the site-specific discussions. Note that our 

suggestions are not based on financial, logistical, or societal implications for each 

location. 

Just Landslide 

The Just landslide is located north of the city of Nowy Sącz on the west side of 

Rożnów Reservoir in the Beskid Wyspowy region of the Outer Western Carpathian 

Mountains. The landslide reactivated in June 2010 following heavy rainfall in May and a 

storm on June 2; it has caused ongoing deformations to a main road (National Route 75) 

through the area, and continual road repair has been required. In addition, several houses 

located on the landslide have been damaged. The landslide toe is exposed at the edge of 

Rożnów Reservoir, and some researchers have speculated that reservoir lowering and 

filling may control movement of the landslide.

The landslide is approximately 300 m wide by 550 m long, with a basal shearzone depth of about 18 m (as measured near the toe). The landslide is developed in 
8

sandstone and shales of the Magura rock series unit (shale flysch deposit). Two existing 

inclinometer/piezometer “nests” (places where multiple sensors are installed) are located

on the northeast half of the landslide, one in the upper third of the landslide and one near 

the toe. In addition, a network of eight GPS survey points is distributed on the landslide 

surface. Piezometers are recorded hourly and manually downloaded periodically, whereas 

inclinometers are monitored monthly. GPS survey points are monitored using geodeticgrade differential-GPS equipment twice per year and following snowmelt and large 

precipitation events.

Our review of the Just landslide was not as thorough as for other sites and 

therefore the following suggestions are based on a limited understanding of this site.

Based on our field visit with PGI personnel, we think that this site is a probable candidate 

for a near-real-time monitoring system. Monitoring protocols should be developed based 

on (1) identifying when deformation of the road is increasing, decreasing, or stable and 

(2) identifying the role of piezometric and reservoir levels on landslide response. 

Monitoring deformation to the road will most likely be possible by using the inclinometer 

already located within the upper portion of the landslide (PGI designation JP-1) or by 

using new, ultra-short baseline (<1 km) differential-GPS monitoring. This latter option 

would take considerable resources in terms of GPS receivers, dataloggers, and datauplink devices, but would provide a means to monitor near-road deformation directly. 

Highly sensitive (10-4 unit strain) soil strain-meters are another possible option. These 

devices might detect deformation earlier than GPS monitoring. Strain measurement at 

selected locations near Highway 75 might be a useful supplement to the displacement 

monitoring. Detailed geomorphologic mapping of the internal structures (for example, 

scarps, shear zones, folds) formed during the recent activation of the landslide would be 

needed to define its kinematic elements and guide instrument placement for displacement 

and strain monitoring. Monitoring of piezometric levels should focus on the basal shear 

zone to provide a direct measure of pore-water pressure that controls landslide 

movement. If the location of the basal shear zone is known, sensors should be placed just 

above this zone to avoid being sheared or damaged. Sensors could be installed using the 

existing piezometers with additional borehole development and by addition of a 

datalogger and either satellite, cell phone, or IP modem uplink. We also suggest at least 

two more piezometer nests in the main body of the landslide because our experience 

indicates that multiple piezometers are typically needed to adequately determine relevant 

pore pressures at the basal shear zone or to resolve questions about landslide hydrology 

(Baum and Reid, 1995; Reid and others 2008). We also suggest synchronous hourly (or 

more frequent) measurements of reservoir level, pore pressure at the toe of the landslide, 

and landslide displacement near the toe to test for direct correlation between reservoir 

level and landslide motion. A pressure-head transducer or water-level sensor located in 

the reservoir below its low water level would be needed in addition to the piezometers 

and GPS units discussed previously. 

Hańczowa Landslide

The Hańczowa landslide is located just north of the village of Hańczowa, on the 

west bank of the Ropa River in the Beskid Niski region at the eastern tip of the Polish 

Outer Western Carpathian Mountains. The landslide has caused periodic deformation and 

closure of an important roadway that accesses resort areas in Wysowa-Zdrój near the 
9

Polish-Slovakian border. No habitable structures are located within the landslide 

boundaries. Due to ongoing concerns with keeping the road open, mitigation measures 

were installed that include horizontal drains, a toe buttress, a 40 m realignment of the 

Ropa River away from the landslide toe, and river bank erosion protection where the 

river cuts the toe. During our site visit, the mitigation appeared to be functioning 

adequately, although we did not check any drains for integrity, nor view any 

instrumentation data. 

The current landslide dimensions are about 280 m wide, 210 m long, and 16-21 m 

deep. The toe of the basal shear zone is exposed in the middle of the Ropa River curving 

upwards at a 23 degree angle relative to horizontal, indicating local rotational motion.

Overall the landslide slopes approximately 8 degrees, and movement appears to be 

mainly translational. Our on-site observations indicate the basal shear zone at the toe is 

composed of plastic, variegated clays with seemingly low shear strength. The landslide 

itself is located within the Magura rock-series unit, represented by beds of Magura 

sandstone and variegated shales (shale flysch deposit). Surficial expression of the 

landslide is fairly subtle due to mature vegetation in the area, however several scarps with 

up to several meters of downward displacement can be discerned amidst the trees. 

Existing instrumentation consists of three inclinometer/piezometer nests, a tipping-bucket 

rain gage on the east bank of the river, and 12 GPS survey points. Piezometers are openhole type with the sensor located at the bottom of each borehole, coincident with 

maximum inclinometer depth. Piezometers are recorded hourly and downloaded 

periodically, whereas inclinometers are monitored monthly. GPS survey points are 

monitored using geodetic-grade differential-GPS equipment twice per year and following 

snowmelt and large precipitation events. 

Based on our site visit and discussions with PGI geologists, we find that this site 

is a likely candidate for performance monitoring. The landslide has already been 

extensively mitigated, and monitoring should focus on whether or not the mitigation 

scheme is functioning to prevent additional deformation to the road. In our opinion, the 

mitigation works probably make this landslide unsuitable for inclusion in an early 

warning network. We find the existing displacement-monitoring instrumentation, 

locations, and schedule adequate for performance monitoring, although we do suggest 

that the piezometers be transitioned to be screened directly above the basal shear zone. If 

desired, it is possible that at least some data could be transmitted remotely to provide a 

near-real-time assessment of site conditions. This could include some form of 

displacement- and additional piezometric-response monitoring. We understand that there 

may be some concerns with vandalism of instrumentation in this area and thus we do not 

suggest using permanent GPS stations to monitor displacement. Rather, some form of 

automated downhole inclinometer measurement would provide a more protected, but still 

meaningful signal. The depth of measurement should be determined based on the basal 

shear-zone depth. Likewise, existing piezometers should also be screened and isolated 

over the basal shear-zone location to provide a more meaningful record of pore water 

pressures that might be affecting landslide motion. Finally, we suggest that some form of 

displacement monitoring also be implemented at the toe. This could be in near-real-time 

mode, using a permanent pulsed laser signal. One or more laser distance meters, 

controlled by a datalogger, could be positioned on the east bank of the river and aimed at 

a target or targets on the west bank. Alternatively, toe deformation could be monitored on 
10

a repeat field-visit schedule by using terrestrial lidar to capture the topography of the 

entire landslide toe. Performing high-resolution change detection on repeat lidar surveys 

could also provide a more complete assessment concerning any future deformation in this 

area. Based on our experience, dense vegetation above the road makes the upper 

landslide region unsuitable for terrestrial lidar monitoring. This type of vegetation would 

prevent the collection of sufficient data needed to construct a useable topographic surface 

model for change-detection monitoring. 

Szymbark (Huciska and Zapadle) Landslides 

The Szymbark-area landslides are located southeast of the town of Szymbark in 

the Beskid Niski region at the eastern tip of the Outer Western Carpathian Mountains.

The landslides, one each on opposite sides of the Bielanka River, are coincident with two 

nearby villages (Huciska and Zapadle). The landslides initially reactivated as a result of 

heavy rainfall in 1997 and have been periodically active since 1997. The Bielanka River 

is thought to control continued movement at these landslides. River effects may include 

direct unloading of the toe through bed erosion, increased pore water pressure on the 

basal shear zone at the toe, or a combination of these effects. In addition to periodically 

blocking the river and damaging the road that runs along the toe of both landslides, these 

landslides have destroyed and damaged several houses in recent years. Average 

landslide-surface velocities are on the order of 0.08 m/yr (approximately 0.4 m in 5 

years) on the Huciska landslide, with higher rates of 0.5 m/yr (approximately 2.5 m in 5 

years) on the Zapadle landslide. 

The Huciska landslide is about 400 m wide and 750 m long with a basal shear 

zone at approximately 12 m depth. The Zapadle landslide is about 750 m wide at the river 

and 975 m long with a basal shear zone at approximately 18 m depth. Basal shear zones 

of both landslides are below river bed elevation. Average surface gradients over the 

length of each landslide are about 7 degrees, and both landslides are located in variegated 

shale-dominated flysch deposits. Because of the importance of the road to area residents, 

PGI installed monitoring equipment on both landslides, beginning with GPS monuments 

approximately 5 years ago and inclinometer-piezometer nests in 2009. A decision on 

future mitigation options to protect the road and existing houses will depend on the 

results of additional landslide investigations. Existing instrumentation at Huciska consists 

of three inclinometer-piezometer nests and seven repeat-GPS survey points. Existing 

monitoring at Zapadle consists of two inclinometer-piezometer nests and eight GPS 

survey points. Our review of PGI documents also indicates that several additional GPS 

survey points exist off the existing landslide boundaries. Piezometers are recorded hourly 

and periodically downloaded manually, whereas inclinometers are monitored manually 

each month. GPS survey points are monitored twice per year and following snowmelt and 

large precipitation events. 

Based on our field visit with PGI personnel and review of site-related documents, 

we find that the existing monitoring locations with regard to inclinometers and 

piezometers is sufficient for capturing future potential road deformation from both 

landslides. River-induced toe erosion is a likely trigger for additional slope movement 

and the existing inclinometers are located effectively near the toe to detect deformation in 

this area. We also find that the monitoring schedule is appropriate (hourly piezometer 

readings and monthly inclinometer readings) for capturing potential hydrologic and 
11

mobilization response. With regard to potential near-real-time monitoring, we find that 

some additional monitoring is possible. Piezometers could be connected to dataloggers 

and up-linked directly to provide a continuous data stream of measurements. Given the 

surficial displacement already measured at the Zapadle landslide (2.5 m in 5 years), it is 

likely that existing inclinometers may not be able to measure long-term movement of the 

landslide before casings are sheared. Therefore, we do not suggest permanent down-hole 

inclinometers for this landslide. Rather, we suggest either installing cable-type 

extensometers in the boreholes, before the casings are sheared, or continuing surficial 

monitoring of the landslide by using the existing GPS survey points. If extensometers are 

selected, these measurements could be connected to a datalogger for direct uplink. If GPS 

monitoring in near-real-time mode is selected, significant upgrades and equipment 

investment will be necessary, including installation of a dedicated, ultra-short-baseline

(<1 km), differential-GPS base-station receiver and dedicated GPS receivers on each 

survey point of interest. We also find that surficial tiltmeter monitoring may be 

ineffective for this landslide due to its shallow surface gradient. One additional 

inclinometer and piezometer nest in the upper parts of both landslides could be installed 

to assist in constraining subsurface basal shear zone motion in those locations. An 

additional GPS survey point in the upper part of the Zapadle landslide complex could 

also be helpful for capturing potential motion directly downslope from the head scarp. 

Piezometers could potentially be installed at different depths coincident with identified 

basal shear-zone depths from inclinometer measurements, such that the pore pressure 

response on the basal shear-zone is quantified. Finally, we suggest that a new streamflow 

gage be installed downstream of the landslides to replace a now-dysfunctional 

instrument. This gage would provide an indication of surficial hydrologic response of the 

region and also give an indication of whether landslide movement has blocked or 

constricted the river. If desired, this gage could be supplemented by one or more laser 

distance meters perpendicular to the channel to observe closure of the stream channel. 

Kłodne Landslide

The Kłodne landslide is located east of the city of Limanowa and west of the city 

of Nowy Sącz, in the Beskid Wyspowy region of the Outer Western Carpathian 

Mountains. Although the Kłodne area is known to contain landslides, local residents 

thought that this particular area was inactive. The most recent activity began at 

approximately 2 a.m. on June 3, 2010, and continued for about 6 hours. The resultant 

deformation, with up to 12 m horizontal displacement at the toe, destroyed 16 houses. In 

addition, several nearby houses on the right flank potentially are in danger if the landslide 

boundaries grow, and a municipal drinking-water supply well, located just off the left 

flank of the landslide, could be threatened by additional landslide movement. 

The current landslide is approximately 300 m wide and 1,000 m long. The depth 

of the basal shear zone over the majority of the landslide is unknown. Overall, the 

landslide surface has gentle slope, averaging approximately 10 degrees over the length of 

the landslide. Surficial expression of the landslide is highly visible in a well-defined head 

scarp, with up to 10 m of vertical offset; an exposed shale-controlled basal shear zone 

dipping at 14 degrees along the upper right flank of the landslide; several sag ponds 

formed within graben; a prominent bulging toe; and many internal scarps, deformed trees, 

and cracked ground. Some cracks are at least 5 m in depth. The landslide is located in 
12

Magura and Sub-Magura rock-series units, present at this locality as a normal flysch 

deposit. Whereas the exposed shale section of the basal shear zone near the head scarp

suggests sliding in this layer, it is unknown if sliding is occurring in this layer throughout 

the landslide. As of September 2010, some mapping of major landslide morphological 

features had occurred, but no instrumentation had been installed.

This landslide is a significant hazard, as continued movement or expansion of the 

landslide boundaries could threaten additional houses and infrastructure. For this reason, 

we suggest that the structural features of the landslide (Fleming and Johnson, 1989; 

Fleming and others, 1999) be mapped in detail on the existing base of high-resolution 

lidar topography and that the site be instrumented with a near-real-time warning system.

In addition, several geodetic-grade GPS survey marks should be established as soon as 

possible to provide a minimum of monthly repeat measurements to determine any 

remaining landslide movement. At least one target should be established on the lower 

right flank, where an existing hazard zone has been delineated, to assist with continued 

monitoring of this area. Geomorphologic mapping should aim to distinguish, as best 

possible, the internal structure of the landslide by using the vast availability of visible 

surficial features (for example, scarps, sag ponds, graben, and displacement vectors from 

trees, electrical posts, and structures) and the existing, post-landslide, airborne lidar data 

set already available for this region. The goal should be to develop a structural/kinematic 

model of landslide mechanics and motion to guide design of a detailed instrumentation 

layout (Baum and Fleming, 1991; Baum and Reid, 1995). Based on the results of 

landslide kinematic mapping, this site may provide a good location to install a series of 

ultra-short-baseline (<1 km) differential-GPS monitoring receivers for near-real-time 

monitoring. It is likely that several GPS receivers located along the toe in regions of 

potential landslide growth and displacement would assist in alerting about potentially 

threatened houses and infrastructure. Flank extensometers might also serve this purpose 

and would provide a potentially less expensive option. At least two inclinometers in the 

main body of the landslide would also assist in constraining basal shear-zone location. 

Given the likelihood that the landslide is responding to water infiltration at depth, the 

basal shear zone should be screened and monitored with piezometers at each boring 

location. Finally, given the large scale and complicated structural and kinematic 

components of this landslide, we think it may provide a good setting for a researchmonitoring program. Research questions could be aimed at delineating how the surface 

morphology is related to either basal shear-zone topography or internal deformation (for 

example, Baum and Fleming, 1991), or address the role of subsurface hydrology in rapid 

versus more creeping components of motion. Depending on the level of instrumentation 

selected for this site, a research monitoring program could be implemented to take 

advantage of the proposed monitoring data streams.

Siercza Landslide 

The Siercza landslide is located in the Pogórze Wielickie region of the Outer 

Western Carpathian Mountains and is situated just outside the city of Wieliczka, an area 

famous for its historical salt-mining district. Mining of the salt deposits to a depth of 

more than 300 m during the past 700 years has led to considerable subsidence in the area, 

and PGI is currently involved in a project to measure this subsidence using synthetic 

aperture radar (SAR) interferometry (Perski and others, 2009). Several damaged houses 
13

have been used as reflectors in previous SAR analyses, and they indicate long term 

(1992-2000) landslide-related, downslope-sliding deformation on the order of 14-18 

mm/yr. In 1997, four houses were destroyed by precipitation-induced landslide 

movement. Additional storm-induced landslide movement in May-June of 2010 caused 

destruction of several more houses and threatened a municipal road. To protect the road, 

the municipality is constructing a soldier pile wall between the road and the head scarp of 

the most recent activation. Currently, 18 occupied houses remain within the mapped 

landslide boundaries, although not all areas of the landslide are equally active.

The currently active landslide is approximately 500 m wide and 600 m long with 

a basal shear zone located 8 to 11 m below the surface near the head and 16 to 24 m 

below the surface in the main body of the landslide. Multiple scarps are evident along the 

downslope length of the landslide and PGI mapping of the head scarp indicates at least 6 

m of vertical displacement. The landslide is located within highly fractured and sheared, 

shale-dominated flysch deposits that have weathered to red-brown clays. In 2008, six 

inclinometer/piezometer nests were installed within the landslide mass, however 

excessive deformation has already destroyed two of these nests. Maximum deformation 

in these two holes occurred at shallow depths between 2 and 4 m, indicating less rapid 

deformation at depth. The remaining inclinometers are measured once per month, 

whereas piezometer levels are logged once per hour and manually downloaded 

periodically. According to PGI personnel, piezometric levels have been generally stable, 

indicating consistent inflow and outflow water volumes to the landslide. During our site 

visit, which occurred after recent rains, we observed many wet areas on the slope surface 

resulting from open seeps and springs. 

Based on our field visit with PGI personnel and review of site-related documents, 

we find that the existing monitoring protocols with regard to inclinometers and 

piezometers are sufficient, but we also suggest some additional instrumentation. 

Specifically, we suggest that casings at inclinometer I-2 and I-6 be fitted with either 

multiple-cabled extensometers or time-domain reflectometry (TDR) probes (coaxial cable 

inside a small diameter, grout-filled PVC pipe and read with a cable tester; see Dowding 

and others, 1989) before the casings are sheared completely due to ongoing deformation. 

This new instrumentation would provide a means for continued deformation monitoring 

(displacement measured using extensometers or depth of shear obtained using TDR) at 

these locations and potentially at multiple depths depending on the quantity of 

instrumentation installed. If fitted with deformation-monitoring instrumentation, 

inclinometer I-2 could also serve as a performance-monitoring device for the soldier pile 

wall currently under construction at the head scarp of the landslide. Alternatively, the 

wall itself could be monitored with repeat, high-accuracy GPS measurements or strain 

gages to measure any wall deformation as part of a performance monitoring plan. 

Additionally, piezometric levels should be carefully monitored, as the wall could 

potentially change the subsurface hydrology by routing groundwater either around or 

below the wall; this may then affect the potential for continued deformation of the main 

landslide mass downslope from the wall. 

Depending on PGI requirements for a hazard warning system, we find that this 

site could serve as a near-real-time monitoring site for early warning. Near-real-time 

monitoring might be desirable here in light of (1) landowner reluctance to implement 

drainage improvements or other engineered mitigation works, (2) potential damage to an 
14

important road, and (3) the brittle nature of unreinforced masonry houses on the 

landslide. Although the site does have some mitigation structures, these are unlikely to 

significantly affect the continued deformation of the landslide below the improvements. 

Thus, continuous surface (through geodetic GPS) or subsurface (through 

inclinometers/subsurface extensometers) deformation monitoring could provide an 

indication of impending landslide-rate increase. Additionally, we suggest that the main 

basal shear-zone depth be monitored with piezometers isolated in that zone so that pore 

water pressures can be measured precisely where they are likely to have the most effect 

on deformation. These monitored pressures could be included in a working, deterministic 

slope stability model, previously calibrated to determine what level of pore water 

pressure is required for landslide movement. 

Łaśnica Landslide

The Łaśnica landslide is located between the Pogórze Wielickie and Beskid 

Makowski regions of the Outer Western Carpathian Mountains near the city of 

Lanckorona. The current landslide boundary is contained entirely within an older mapped 

landslide deposit. The current reactivation began on May 19, 2010, and has destroyed or 

damaged 30 homes. In addition to continued deformations to structures, the landslide also 

has the potential to block a stream (Potok Cedron) located just below the landslide toe. 

The current landslide reactivation is approximately 300 m wide and 350 m long 

with a basal shear zone at about 14-m depth and overall ground surface inclination of 

14.6 degrees. Surficial expression of the landslide includes hummocky ground and about 

three 40-cm-tall internal scarps near the head. The landslide is a dip slope (15°) feature 

within a sandstone-dominated flysch with massive sandstone blocks and very thin shales. 

Portions of the landslide mass have been mapped as surficial colluvial deposits up to 10 

m in thickness. As a result of the continued threat to homes in the area, the local 

municipality drilled two borings within the landslide boundaries. The first boring, located 

at about the landslide mid-slope, quickly sheared at about 14-m depth in response to 

surface deformations of up to 21 cm/day before development as an inclinometer could be 

completed. The second boring, located closer to the head scarp, was successfully 

developed as an inclinometer and has not yet sheared. It is currently being monitored on a 

monthly basis. No piezometers were installed during the drilling effort. According to PGI 

personnel, active seepage and slumps have been observed in the colluvial layer of the 

landslide mass, but no seepage above the head scarp has been observed. 

Depending on PGI requirements for a hazard warning system, we find that this 

site could serve as a near-real-time warning system site. Monitoring continued 

deformation and subsurface hydrologic response of the landslide would serve to provide 

potential warning of increasing deformation rates or the progress of pore pressure 

generation along the basal shear zone. Before location and selection of instrumentation, 

we suggest that a thorough investigation of the subsurface deposits, through either 

existing or new drilling and geomorphologic mapping of the surface expression of the 

landslide, be performed. This mapping would guide placement of either surface (GPS) or 

subsurface (downhole extensometer) deformation instrumentation and subsurface 

hydrology (piezometer) monitoring instrumentation. As at the other sites, we suggest that 

piezometers be screened over the interval immediately above the basal shear zone (to 
15

prevent shearing of instrumentation) to provide an indication of pore water pressures that 

could lead to instability of the landslide.

Łazki Landslide

The Łazki landslide is located in the Beskid Małego region of the Outer Western 

Carpathian Mountains north of the city of Żywiec. The landslide is adjacent to 

Międzybrodzie Reservoir, a flood-control reservoir built prior to 1939. Reactivation of 

this landslide began in May 2010, with average displacements of 20 cm/day. According 

to police authorities, displacements continued to be up to 1 cm/day during the time of our 

site visit (mid-September 2010). Seventy homes, mostly summer cottages, are directly 

affected by continued landslide motion, and many of these homes have been rendered 

uninhabitable due to excessive wall and (or) foundation deformation. In addition, there is 

debate about whether or not rapid acceleration of the landslide could occur and lead to a 

landslide-generated tsunami in Międzybrodzie Reservoir. Waves from such an event 

could potentially overtop the dam located roughly 1.5 km downstream from the landslide. 

The currently active landslide is approximately 350 m wide and 500 m long. The 

head area slopes as much as 36 degrees, but the overall ground-surface slope from head 

to shoreline is about 8 degrees. The basal shear-zone depth has been inferred to be at least 

30 m as determined by observations of the reservoir side-slopes at low-water levels, 

where no basal shear zone could be located. Thus, previous investigators have suggested 

that the basal shear zone is below this level. At least five major internal scarps have been 

mapped, each with about 2-3 m horizontal displacement and 1-2 m vertical displacement.

Near the current head scarp, an older relict graben feature with about 6 m vertical 

displacement is visible. Near the toe, some buildings show clear effects from 

compressional motion, suggesting a passive zone at this location. Understanding the 

surficial expression of the landslide is further complicated by observations of landslide 

sections containing buildings with relatively little or no damage, as well as landslide 

sections containing buildings with considerable damage. Thus, it is likely that some parts 

of the landslide are translating downslope without excessive internal deformation. PGI 

geologists have suggested that this could be an example of a complex block-slide type 

landslide. The landslide is located in a highly fractured sandstone-dominated flysch 

(Godula beds of the Silesian rock series unit) and cuts across bedding. Thick colluvial

deposits are found throughout the site. Near the head scarp, the colluvium thins 

considerably to less than 0.5 m depth. PGI geologists have investigated the overall 

geological structure of the landslide and hypothesize that the upslope boundary may be 

formed in a joint-controlled tectonic framework, as evidenced by uncomformably 

oriented sandstone beds in contact with one another. 

Depending on PGI requirements for a hazard warning system, we find that this 

site could serve as a near-real-time warning system site. In addition, given this site’s 

proximity to a large reservoir and the possibility that sudden deformation could lead to 

landslide-generated tsunami overtopping of the dam, this site may also be a good 

candidate for implementation of a real-time warning system. However, probability of 

rapid catastrophic movement seems low given the gentle overall slope (8°) and the 

landslide’s similarity to other slow-moving landslides in the region. Nevertheless, 

determination of the hazard posed by landslide-reservoir interactions should first be 

established through detailed landslide geomorphologic mapping and development of 
16

appropriate deterministic slope stability analyses. These analyses may help guide whether 

a real-time warning system is needed at this location. If these analyses can determine 

whether or not future landslide movements are expected to be rapid (for example, a major

drop in peak to residual shear strength, or other rheological-type analysis), the landslide 

may not pose the hazard necessary to implement such a system. Regardless of the type of 

monitoring selected, we suggest that the site be first mapped in detail to guide 

instrumentation selection and placement. The goal of the mapping should be to identify 

primary active structures and landslide extents at the toe and to make an assessment of 

landslide kinematics. Whereas the majority of mapping likely can be performed by 

conventional surface methods, we suggest that large-diameter borehole mapping be 

considered to identify basal shear-zone depth. Such drilling would need to be done at 

least 30 m above reservoir level to avoid flooding of the hole. In addition, some form of 

bathymetric mapping of the reservoir side slopes may provide a better indication of the 

location and extent of the landslide toe. We suggest investigating the use of airborne lidar 

for mapping the terrestrial portion of the site and potentially using a blue/green waterpenetrating laser for the submarine portions of the site. However, any use of airborne 

laser mapping should carefully investigate the likely ground returns expected from such a 

survey, as portions of the site are highly vegetated. Given the potential complexity of the 

landslide itself, we find that ultra-short baseline (<1 km) differential GPS is the most 

appropriate type of instrumentation for detecting potential landslide movements. 

However, this may require many (6+) receivers to adequately monitor all active areas of 

the landslide. At least two receivers would be needed in the relatively undeformed and 

apparently most rapid-moving part of the landslide. GPS monitoring could be 

supplemented by extensometers or laser distance meters at the landslide flanks and head 

scarp. Piezometers at the basal shear zone would be needed for long-term monitoring and 

assessment of the stability of the landslide mass. We recognize that for safety reasons, all 

subsurface exploration might need to be postponed until the landslide’s current 

movement has stopped. If real-time monitoring and associated protocols are selected, any 

data streams resulting from instrumentation must be adequately analyzed and 

disseminated, such that all affected parties know the implications of any potential alerts

in a timely manner. Such protocols might address the following questions: 

• Will shoreline areas be evacuated?

• Will reservoir levels be drawn down, and if so, will this further affect landslide 

instability through a rapid drawdown scenario? 

• Will below-dam inhabitants be evacuated? 

Siedloki Landslide 

The Siedloki landslide is located on the side of a steep valley in the hamlet of 

Siedloki, east of the village of Milówka, in the Beskid Żywiecki region of the Outer 

Western Carpathian Mountains. The area had been mapped previously as an inactive 

landslide deposit. Movement was first noticed on September 3, 2010, and by September 

14, 2010, horizontal and vertical displacements of about 7.5 m and 3 m, respectively, had 

occurred. Movement began following a period of prolonged rainfall (approximately 100 

mm precipitation in two days). At the time of our site visit, seeps and wet ground were 

visible in many locations on the landslide surface. Four houses were destroyed by 
17

deformation and several others were damaged. Additionally, the landslide toe destroyed 

the single road accessing approximately 50 additional homes beyond the landslide limits 

and completely blocked a stream (Potok Milowski) at the base of the valley. At the time 

of our reconnaissance (September 14, 2010), a new stream channel had been dredged 

through the landslide toe, and surveyors were laying out a temporary road through the 

landslide debris to access the currently isolated homes upstream of the landslide. 

The currently active landslide is approximately 280 m wide and 430 m long with 

an unknown depth. Surficial expression of the landslide is evidenced by distinct head and 

side scarps, as well as internal scarps, cracked ground, and graben. In general, landslide 

features are suggestive of an undulating basal shear surface at depth, although little is 

currently known about the basal shear zone. The landslide is developed in sandstones and 

shales of the Magura rock series unit, present at this locality as a normal flysch deposit.

In general, bed thickness is largest at the head scarp and noticeably thinner at the toe. 

Regional bedding is folded and dips in-slope (opposite to the direction of topographic 

slope) over the landslide surface as part of a structural anticline. Due to the recent 

reactivation of this landslide, there is currently no instrumentation installed. 

Our general suggestions include performing surficial geomorphologic mapping to 

define landslide elements and geotechnical drilling to determine basal shear-zone depth. 

Upon completion of drilling, borings should be developed with 

inclinometers/piezometers. We suggest, at a minimum, three inclinometer/piezometer 

nests aligned along the main axis of the landslide to provide a longitudinal section 

parallel to the movement direction of the landslide. Piezometers should be developed to 

sample pore-water pressure at the basal shear zone. Given this landslide’s influence on 

nearby residences, we suggest that it be developed as a near-real-time warning system 

monitoring site. Instrumentation should include downhole tiltmeters and (or) cable 

extensometers, depending on current rates of landslide motion, and ultra-short baseline 

(<1 km) differential-GPS monitoring in areas of potential surface deformation. These 

should be monitored hourly, or more frequently during periods of rainfall, to provide an 

indication of impending, large-scale landslide deformation. This site may prove to be a 

good candidate for repeat terrestrial-lidar-based monitoring. In addition to the surface 

being free of significant vegetation in many locations (thus making surface 

morphological features visible), the site also has line-of-site to the hillslope opposite the 

landslide, which offers a suitable location for a laser instrument. A near-perpendicular 

line of site typically maximizes lidar point-cloud density over a wide area from a single 

vantage point. A potential limitation for terrestrial lidar monitoring is most lidar 

instrument’s limited range, as potential laser-instrument locations on the opposite valley 

slope are about 1,000-1,200 m from the upper areas (farthest areas) of the landslide 

surface. However, several vendors manufacture lasers with this distance capability, thus 

an investigation of the potential for implementation of this method is warranted. If 

movement of this landslide continues, its potential for blocking the stream, Potok 

Milowski, and creating upstream and downstream flooding hazards may warrant a 

separate real-time warning system. Streamflow gages upstream and downstream of the 

toe of the landslide could be monitored at hourly or shorter intervals to detect upstream 

ponding and downstream reduction in flow (Harp and others, 2008). In addition, laser 

distance sensors positioned on the south bank of the stream could measure advancement 

of the landslide toe at the same intervals. It is unlikely that terrestrial lidar monitoring 
18

Table 1. Summary monitoring suggestions for landslide sites visited in Poland, 

September 2010. 

Landslide 

name Risk description Monitoring purpose

Current and 

suggested

observations 

General suggestions1

Just Road subject to 

damage.

Near real 

time

Displacement, 

pore pressure, 

precipitation

Possibly add strain measurements 

near road, add piezometers, 

monitor reservoir level

Hańczowa

Road subject to 

damage.

Mitigation 

measures 

installed.

Performance

Displacement, 

pore pressure, 

precipitation, 

strain

Continue current monitoring and 

add periodic observations of toe 

buttress

Szymbark 

(Huciska, 

Zapadle)

Road and houses 

subject to damage.

Near-realtime

Displacement, 

pore pressure, 

precipitation, 

streamflow

Add GPS or borehole 

extensometers, piezometers, and 

inclinometer upslope, possibly add 

streamflow gage or observe stream 

closure using laser

Kłodne

Houses subject to 

damage.

Municipal water 

supply well and 

additional homes 

threatened.

Near-realtime, 

Research

Displacement, 

pore pressure, 

precipitation

Structural/kinematic mapping2 and 

basal shear-zone depth needed, 

potential enlargement needs to be 

monitored, good candidate for 

GPS, possible flank extensometer

Siercza Roads and houses 

subject to damage.

Near-realtime, 

Performance

Displacement, 

pore pressure, 

precipitation

Continue current monitoring and 

add GPS or downhole 

extensometer, observe potential for 

downslope enlargement

Łaśnica Roads and houses 

subject to damage.

Near-realtime

Displacement, 

pore pressure, 

precipitation

Structural/kinematic mapping2

needed, add GPS or extensometers

and piezometers

Łazki

Houses subject to 

damage. Threat of 

landslide-induced 

tsunami and 

nearby dam 

overtopping.

Near-realtime or 

Real-time

Displacement, 

pore pressure, 

precipitation

Structural/kinematic mapping2 and 

basal shear-zone depth needed, add 

GPS or extensometer at flank, add 

inclinometers, and collect nearshore bathymetry

Siedloki

Houses subject to 

damage.

Landslide toe 

overruns access 

road to village and 

blocks stream at 

toe with flooding 

hazard.

Near-realtime

Displacement, 

pore pressure, 

precipitation, 

streamflow

Structural/kinematic mapping2 and 

basal shear-zone depth needed, add 

GPS or extensometer at flank, 

possible candidate for terrestrial 

lidar or total station monitoring of 

landslide body or laser monitoring 

of toe displacement, possible 

candidate for streamflow gage 

monitoring

1

This list is not comprehensive. Additional suggestions and details are provided in the text of this report.

2

Structural/kinematic mapping requires high-resolution topography as obtained, for example, by airborne 

lidar. 
19

from clearings high on the opposite valley slope would detect toe deformation because of 

poor toe visibility from that vantage point. 

Example of a Near-Real-Time Warning System

We present the following description of a near-real-time warning system 

monitoring approach for a hypothetical landslide in the Polish Carpathians. Here, we 

assume that the purpose of monitoring is to monitor and detect when landslide-prone 

conditions are occurring in a particular region. The landslide, along with several others, 

would thus have been selected previously to be representative of typical landslide 

geometries and topography for the region under investigation. Because deep-seated 

landslides are typically complicated and potentially unique with respect to specific 

hydrologic conditions and ensuing motion, any attempt at regional forecasting should rely 

on the results from several monitored landslides. In this hypothetical example for one 

landslide, we assume that the landslide geometry, basal shear-zone depth, and general 

subsurface hydrology are known from previous investigations that included drilling three 

inclinometers and a single groundwater observation well. We also assume that direct line 

power and cell phone reception are available at the site. 

The hypothetical landslide (fig. 2) is 400 m wide and 600 m long and occurs in 

normal flysch and overlying colluvium. The longitudinal topographic profile of the 

landslide surface is slightly concave upward with an overall slope of 8 degrees from the 

head scarp to the toe. Measurements at three inclinometers indicate the basal shear zone 

is 15-18 m deep in the main body of the landslide and 13-m deep near the toe. Prior to 

conversion of the site to a near-real-time monitoring site, one of the inclinometer 

boreholes sheared, preventing any additional instrumentation in this hole. The toe of the 

landslide is adjacent to a stream, which erodes the toe during high flows and floods. 

Water table depth ranges from about 5 to 8 m annually at an observation well near the 

center of the landslide, and occasionally, water has been observed seeping from the toe 

during the latter part of the wet season. Annual displacement ranges from 0 to 0.2 m 

during average years and has been as much as 1.5 m during extremely wet years, such as 

1997 and 2010. Careful geomorphologic mapping of landslide structural features, such as 

scarps, cracks, shear zones, and folds, combined with the analysis of displacement data 

revealed the extent of zones of longitudinal stretching and shortening. High-resolution 

topography derived from airborne lidar or digital photogrammetry provides a satisfactory 

base for such detailed mapping. The upper 120 m is stretching longitudinally, a neutral 

(relatively undeformed) zone exists 120-250 m downslope from the head scarp, and the 

lower 350 m of the landslide (250-600 m downslope from the head scarp) is shortening 

longitudinally. The neutral zone is usually the most rapidly moving part of the landslide 

(Baum and Fleming, 1991). 

Table 2 summarizes our suggested monitoring plan for the hypothetical landslide. 

The plan includes a basic monitoring system that could be used at all landslides 

monitored by PGI, and it lists extra sensors that could be added where needed at 

particular landslides. Listed quantities represent the minimum number of sensors needed 

to observe and measure surface deformation, subsurface water, and weather conditions. 

Three stations for measuring pore pressure at the basal shear zone and displacement 

within the slide mass, along with a basic weather station constitute the core sensors 

(“high” priority) for the monitoring system. These stations are located in the upper, 
20

Figure 2. Sketch map, cross section, and details, of hypothetical landslide. 

W, groundwater observation well; I, borehole inclinometer (“×” through the 

symbol denotes that the casing has been sheared at the base of the landslide 

prior to conversion to a near-real-time monitoring site); P, piezometer; E, downhole extensometer; SE, surface extensometer (an alternative to GPS where the 

landslide has well-developed head scarp or lateral shear zone at flanks); GPS, 

station for continuous GPS monitoring; GPS Base, GPS base station; LDM, laser 

distance meter; SM, soil-moisture sensors and (or) tensiometers; SSG, soil-strain 

gage; T, borehole tiltmeter; M, meteorological sensors (for example, rain gage, 

thermometer, barometer); DAQ, data-acquisition system or datalogger; COM, 

communications link; CAM, camera. The GPS base station, data-acquisition 

equipment, communications link, camera, and meteorological sensors are 

located well off the landslide on stable ground. The observation well and 

inclinometer holes (shown as open circles) are assumed to exist from an initial 

investigation, prior to installation of equipment for near-real-time monitoring.
21

middle, and lower sections of the landslide along the main axis, whereas the weather 

instruments may be located on or off the landslide, as convenient. Two rain gages are 

suggested for redundancy. The system may be supplemented with additional sensors 

(“medium and “low” priorities) for observing infiltration of surface water (water content 

sensors, tensiometers), complex deformation (tiltmeter, soil-strain gage), and toe 

displacement (laser distance meters), and with a digital camera for recording daily images 

of the site. Additional piezometers between the basal shear zone and the seasonal low 

water table would help in defining flow directions and hydraulic gradients within the 

landslide. Hourly data transmission from all sensors is probably adequate for this type of 

monitoring, although it could be more frequent during times of landslide movement. 

Several options exist for displacement measurement, each with various 

advantages and disadvantages. For example, upon installation, inclinometer casings can 

be fitted with a permanent stack of borehole tiltmeters to automate traditional 

inclinometer measurements. These can be read as frequently as desired and provide a 

depth profile of displacement in two orthogonal directions, but at considerable cost. Once 

landslide displacement exceeds several centimeters, the tiltmeter in the basal shear zone 

will either break or tilt beyond its useful range. Downhole extensometers give an 

approximate measurement of downslope displacement, are usually quite sensitive to 

small displacements, and can measure displacements of tens to hundreds of centimeters 

with adequate construction and maintenance. Extensometers on the surface across the 

flank or head scarp can have similar performance. Laser distance meters have the 

advantage of making noncontact measurements, providing relatively rapid response, and 

are of high accuracy. In addition, some laser distance meters are capable of making 

measurements directly on the ground surface, rather than using a target. Laser distance

meters have somewhat higher power requirements (2-6 W) than other sensors; datalogger 

control ports can be used to switch to power on and off, and thus conserve power. Beam 

trajectory is fixed upon installation; consequently, the observed point on a moving 

landslide may change through time and introduce uncertainty into the displacement 

measurement. 

GPS monitoring is capable of providing three-dimensional displacement 

measurements with subcentimeter accuracy. Such measurements usually require highcost dual-frequency (L1, L2) receivers and commercial or open-source software may be 

available to perform the necessary processing and plotting in near real time (see 

http://www-gpsg.mit.edu/~simon/gtgk/index.htm). Although the technologies exist for 

real-time GPS monitoring using geodetic-grade equipment, some in-house development 

would probably be required to make the technologies work together to meet PGI’s needs. 

High-accuracy displacement measurements in near real time have also been achieved 

using inexpensive single frequency (L1) receivers, ultra-short (<1 km) baselines, and 

custom software (Reid and others, 2008; Harp and others, 2008). Unfortunately, we know 

of no complete, currently available, commercial or open-source solutions for this 

application. PGI could probably develop this capability in-house through collaboration of 

its GPS and IT specialists. In all cases of hydrologic and displacement instrumentation, 

additional redundant sensors may be desired in cases where monitored data streams tie 

directly into a warning system. As such, paired piezometers or extensometers, for 

example, should be considered, but are not detailed as a part of this hypothetical example. 
22

Table 2. Equipment for near-real-time monitoring of hypothetical landslide. 

Location Depth 

(m) Sensor or equipment type1

 Quantity Priority

Zone of 

longitudinal 

stretching

(0-120 m)

10 Piezometer2 1 Medium

15 Piezometer2 1 High

0 Down-hole extensometer3 1 High

1.5 Soil strain gage/soil extensometer4 1 Medium

Neutral zone

(120-250 m)

10 Piezometer2 1 Medium

18 Piezometer2 1 High

0 GPS receiver5 or surface extensometer3 1 High

0.5, 1, 2 Water content sensor and (or) tensiometers6 3 Medium

Zone of 

longitudinal 

shortening

(250-600 m)

8 Piezometer2 1 Medium

13 Piezometer2 1 High

0 Down-hole extensometer3 1 High

0 GPS receiver5 1 High

Toe 0 Laser distance meter7 2 Medium

5 Borehole tiltmeter8 1 Medium

Flank or Crown 

(Off slide)

0 Tipping bucket precipitation gage9 2 High

0 Barometer10 1 High

0 Air temperature sensor11 1 High

0 GPS base station5 1 High

0 Datalogger12, enclosure, grounding rod, 7-Amphour (or larger) battery and charger 1 High

0 Multiplexer13 1 High

0 Vibrating wire interface14 1 High

0 IP modem and antenna15 1 High

0 Still camera16 or webcam 1 Low

Office --

Windows or LINUX PC or server, Internet 

connection, Datalogger communication and 

control software17

1 High

1

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement 

by the U.S. Government. 

2

Casagrande type, with 0.5-m-long porous tip, and pressure sensor, similar to Geokon 4500 series vibrating 

wire sensor (http://www.geokon.com/), Slope Indicator, Inc. model 52611020 vibrating wire piezometer 

(http://www.slopeindicator.com/). See Appendix A, instrument installation.

3

A 6-mm braided-steel cable is anchored at the bottom of the inclinometer casing. A spring provides 

tension to counteract the weight of the downhole cable. The free end of the braided cable is attached to a 

cable-extension transducer (similar to Celesco Transducers, model PT8101, http://www.celesco.com/ or 

those by UniMeasure, http://www.unimeasure.com/). The same instrument, with a lighter cable can be used 

as a surface extensometer for landslides with well-developed flank or head scarp at lower cost than dual 

frequency GPS.

4

Similar to Geokon Soil Extensometer Model 4435. 

5

Similar to equipment offered by Ashtech (http://www.ashtech.com/) or Trimble (http://www.trimble.com/) 

for subcentimeter accuracy surveys, with software similar to GAMIT (http://wwwgpsg.mit.edu/~simon/gtgk/index.htm) or Waypoint (http://www.novatel.com/products/waypoint-software/). 

6

Similar to Decagon Devices, Inc., Model EC-5 Soil moisture sensor (http://www.decagon.com/) and UMS 

tensiometer model T8 (http://www.ums-muc.de/en/service_navigation/home.html). 

7

Similar to Sick AG, DT50 or DMT10 series laser distance sensors, depending on the distance between the 

target on the landslide toe and a stable location for mounting the sensor (http://www.sick.com/). 

8

Similar to Applied Geomechanics Model 906 Little Dipper In-Place Inclinometer 

(http://www.carboceramics.com/agi/900-series/). 
23

9

Similar to Met One Instruments, Inc. 300 series precipitation gages (http://www.metone.com/) Two rain 

gages are suggested for redundancy.

10Similar to Met One Instruments, Inc. Model 092 Barometric pressure sensor; otherwise, it is acceptable to 

use the same model sensor for above ground installation as is used in the piezometers below ground, as 

long as they are used only for pressure compensation of the sealed sensors (see note 2 above). 

11Similar to Campbell Scientific, Inc., 107-L Temperature Sensor (http://www.campbellsci.com/). 

12Similar to Campbell Scientific, Inc., CR1000 measurement and control system. Battery rating for solarpowered systems depends on local climate and sun exposure. 

13Similar to Campbell Scientific, Inc., AM16/32B Multiplexer.

14Similar to Campbell Scientific, Inc., AVW200 vibrating wire interface, used with vibrating wire 

piezometers.

15Similar to Sierra WirelessTM AirLink Raven XT modem, with YAGI or omnidirectional antenna 

(http://www.getwirelessllc.com/Airlink.cfm). 

16Similar to time lapse package offered by Harbortronics (https://www.harbortronics.com/) unlike a 

webcam, these images would be stored onsite.

17Similar to Campbell Scientific, Inc., LoggerNet software, for large networks of remote monitoring 

stations, software similar to LoggerNet Admin is needed. OPC software could also be used. Telephone 

modem, radio or satellite base station, or other communications peripheral devices may be needed if remote 

sites are using cellular modems, radio, or satellite communications.

For this hypothetical example, the datalogger and peripherals are housed in a 

weather-tight enclosure on stable ground near the edge of the landslide where AC 

electrical power is available. A wireless IP modem would provide rapid communication 

(similar to text messaging) between the monitoring station and PGI’s computer network. 

At remote sites where cellular coverage and AC power are not available, solar power and 

radio or satellite communication would be needed. All sensors are connected to and 

communicate with the datalogger by means of signal cables. Wireless communication 

between the sensors and dataloggers is also possible where needed; however, it adds to 

the cost and complexity of the system. One or more multiplexers may be needed to 

conserve channels on the datalogger by allowing the datalogger to use only one or two 

channels to read several sensors of the same type. For example, using the vibrating-wire 

interface in series with a multiplexer could allow six piezometers and the soil-strain gage

to be read using only two datalogger channels, one for signal and one for temperature. 

Appendix A provides additional suggestions for installation of remote automated 

landslide-monitoring stations. 

Field data collection and monitoring, whether manual or automated, are labor 

intensive and therefore costly activities. A common pitfall in many landslide 

investigations is underestimating the true costs of instrumental monitoring programs. 

Estimating the cost of the initial investment in equipment and installation is relatively 

straightforward. An estimate can be obtained by compiling unit prices for the selected 

instrumentation from table 2, and computing the total based directly on the selected site 

instrumentation layout. However, in addition to the initial, one-time costs of background 

fieldwork and research, and equipment acquisition and installation, the costs of data 

collection, surveillance (monitoring system performance and data flow), repairs, 

maintenance, and data processing continue for the life of the project. This may include 

replacement of instrumentation due to exhaustion of its service life from weathering and 

continuous use. Although the service life of instruments varies considerably, five years 
24

seems like a reasonable average based on our experience. Thus, depending on the 

duration of the project, the continuing costs can approach or, in some cases, exceed the 

initial investment (Baum and others, 2008). 

In an actual near-real-time monitoring system, data from this landslide would be 

periodically automatically transmitted, graphed, and then analyzed by PGI personnel to 

deduce if landslide movement was occurring or was imminent. However, the data might 

also be used in conjunction with data from other nearby monitored landslides to 

determine if landslide-prone hydrologic conditions exist, in general, for a given region. If 

any of these conditions were determined to be occurring, it would be the duty of the 

personnel analyzing the data to take appropriate steps to (1) verify the prognosis of the 

data analysis and (2) communicate with appropriate internal (PGI staff) and external 

(public officials) personnel about the meaning of the prognosis in terms of public 

response. These actions should follow a carefully, predetermined decision matrix with 

regard to issuing notifications and (or) warnings.

Managing Public Perceptions about Real-Time Landslide 

Monitoring and Early Warning

Although this report is primarily about the technical aspects of real-time and nearreal-time landslide monitoring, sociological issues and challenges also influence the 

effectiveness of warning systems. A complete warning system includes protocols for 

disseminating warnings and actions to take depending on the level of warning. 

Development of a real-time monitoring and early-warning system for landslides in the 

Polish Carpathians will put PGI and landslide monitoring increasingly in the public eye. 

A wide variety of questions may arise from the public, such as: 

• What are landslides and how do I know if my house is on one? 

• What should I do if PGI has issued a landslide warning? 

• How will landslide monitoring reduce losses or help the public? Is the benefit worth 

the expense? Is it an appropriate expenditure of public funds? 

• If PGI is monitoring all those other landslides, shouldn't they also be monitoring the 

one that affects my property? 

• If PGI is monitoring the landslide on which my village is built, will it (the 

monitoring) keep us safer? Will the government compensate us for losses?

Such questions arise out of the public’s unfamiliarity with relatively infrequent 

phenomena, such as landslides, and some people may assume that if the government is 

doing anything about a problem that it is assuming full responsibility. Additional 

problems associated with false alarms on the one hand, or failure to warn on the other, 

might result from inherent uncertainties in monitoring data or equipment malfunction. 

Depending on existing laws, such errors may bear financial liability (especially failure to 

warn if fatalities or serious injuries occur). Awareness and careful consideration of these 

and related issues may influence planning of PGI’s monitoring program. Dialogue with 

local and regional authorities, as well as with the emergency-management community 

and possibly the Polish national weather bureau, will be needed to determine how 
25

warnings will be handled, what should happen when a warning is issued, and who will be 

responsible. Once PGI is prepared to address questions about purpose, scope, cost, 

procedures, roles, responsibilities, liability, and so on, a well-managed public-information 

campaign will help manage public expectations about landslide monitoring. Sound legal 

advice may be beneficial as well. For additional information on the complexities of 

warning systems, see Wilson (2004) and Baum and Godt (2010). 

Finally, it is important to note that monitoring up to 100 landslides, as PGI is 

proposing to do, should be viewed as an ambitious task. Considerable resources, 

including continuous labor, will be needed to maintain and operate such a system. There 

are few, if any, existing systems of this scope currently operating in the world (for 

example, the USGS currently monitors about 10 to 15 sites nationwide), and thus, PGI 

should be prepared to put forth considerable investment and confront significant 

challenges in pursuing this goal.

Potential Research Questions To Be Answered By 

Monitoring

If PGI embarks on a program of real-time landslide monitoring and (or) near-realtime landslide monitoring for early warning, a research and development effort will be 

needed. This effort should initially be aimed at developing monitoring procedures and 

determining research questions suited to landslides in the Carpathians, followed by a 

period of time in which the accuracy and timeliness of warnings can be gradually 

improved. The following list of questions is incomplete and touches on only a few of the 

more obvious topics that could merit further research. Some of these questions address 

landslide activation, whereas others address monitoring techniques and warning methods. 

At least some of the research will require laboratory or other techniques in addition to 

field monitoring. Real-time monitoring allows the collection of synchronous data on 

landslide movement, hydrological conditions, and related processes. Data synchronicity 

is necessary for resolving cause-and-effect relationships, and clearly understanding 

processes that can contribute to predicting landslide behavior. 

• How does water move from the surface to the basal shear zones? How does water 

movement affect timing of landslide movement in relation to rainfall and snow melt?

• Can landslide surface geomorphic expression be linked to geometry of the basal shear 

zone or must internal deformation (dilation or contraction) be taken into account in 

deterministic landslide models?

• Can rapid versus creeping areas of landslide motion be linked to differential 

subsurface hydrologic response? 

• Can linkages be established between pore pressure response at the basal shear zone 

and landslide movement? 

• How similar are basal shear zone geotechnical properties of landslides throughout the 

Carpathians?

• Do regional patterns of hydrological conditions (pore pressures, stream discharge, 

antecedent precipitation, and so on) exist that can be used as a basis for alerting the 

general public of increased potential for landslide reactivation?
26

• What is the role of reservoir operations, if any, on landslide pore pressure and 

movement in these particular settings?

• Are ground strains detectable in landslide deposits before ground cracking becomes 

apparent or displacement becomes measurable? 

• How well do inhabitants of the Carpathian region respond to landslide alerts? 

Conclusions

Landslide monitoring is a complicated process, both technically and 

sociologically. On the one hand, landslides are, by their nature, very complex and require 

sophisticated research tools and analysis techniques to achieve a detailed understanding 

of expected motion and acceleration. On the other hand, the implications of detecting 

motion or impending activation have important ramifications for affected landowners, as 

well as for officials charged with maintaining public safety and protecting societal loss.

Any effort to establish landslide warning systems must rely heavily on the skills and 

technology available from scientific and engineering research, as well as on creating a 

solid framework conducive to transferring relevant information to those who need it 

most.

In this report, we have outlined substantial background information on state-ofthe-art landslide-monitoring techniques to assist PGI with on-going concerns about recent 

landslide reactivations in southern Poland. This information, coupled with site-specific 

suggestions for eight landslides visited by USGS personnel in September 2010, provides 

a framework for developing local monitoring protocols for deep-seated landslides. 

Developing regional strategies, based on monitoring several representative landslides, 

will require additional research with regard to how these particular landslides may be 

used as proxies for regional expectations. In our suggestions, we have highlighted the 

importance of selecting an appropriate monitoring strategy, consistent with expectations 

for the use of the data to be collected. Once a strategy is chosen for each site, suggestions 

for instrument selection and location can be implemented. Sensor deployment should be 

further refined based on additional site-specific geologic and geomorphologic mapping. 

Using the monitoring strategies outlined in this report, PGI should be well-positioned to 

assess landslide activity and assist with making appropriate decisions concerning 

landslides in the Polish Carpathians. 

Acknowledgments

This report was prepared in collaboration with the Polish Geological Institute, 

Warsaw, Poland. Ingrid Verstraeten (USGS, International Programs), and Wojciech 

Brochwicz-Lewinski and Ilona Smietanska (PGI-NGI, International Cooperation Section) 

conceived and developed this cooperative project between Poland and the United States. 

Mark Reid, Jeffrey Coe, and Ed Harp of the USGS provided detailed comments that 

improved the content of this report. 
27

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29

Appendix A. General Considerations for Real-Time and 

Near-Real-Time Monitoring

Power

• Available line power with battery backup is generally more dependable than solar 

power with batteries.

• A regular maintenance schedule for battery replacement is needed.

• Recording and transmitting raw voltages from sensors reduces overhead on 

dataloggers. Conversion to engineering units can be done automatically at the office; 

this also makes it easier to correct conversion errors or apply improved calibration 

factors or formulas to data collected previously. 

Communications

• When available, wireless IP modem connections are desirable for data transmission; 

however, uplink of data can include a number of options such as cell phone, satellite, 

spread-spectrum or dedicated radio link, and land-line telephone. 

Instrumentation Layout

• Landslide instrumentation is often best installed in stages. The first stage of 

subsurface instrumentation seeks to determine location of the basal shear zone and 

depth of groundwater. The second stage seeks to refine pore pressure measurements 

at the basal shear zone and fill in gaps identified during the first stage (Baum and 

Reid, 1995). 

• Ideally, piezometers should be screened over the depth interval just above the basal 

shear zone. This provides important data that may be used in deterministic assessment 

of slope stability.

• Equipment redundancy, in the form of multiple installed instruments, greatly 

improves reliability for real-time operational monitoring. 

• Some form of independent measurement (for example, calibrated tape measure or 

water-level sensor) is useful for periodic recalibration of extensometers, piezometers, 

and many other types of sensors. 
30

Instrument Installation

• Buried cables should be protected from burrowing animals, preferably in a flexible 

metallic conduit. The conduit need not be waterproof so long as cable insulation is 

intact and all splices are waterproof. Cables exposed above ground also need to be in 

flexible metal conduit to prevent animals from chewing the insulation.

• Extensometer cables need to be protected from animal disturbance by placing them 

either high above the ground or in an enclosure. 

• Some types of electronic piezometers are made for direct burial, with the advantage 

of faster response time and more accurate pressure measurement than Casagrande 

piezometers. However, for long-term installations, sensor repair or replacement is 

much easier and less costly when using Casagrande piezometers monitored with a 

removable electronic piezometer or water-level sensor. 

• In all cases, sufficient strain relief should be included for cables, such that upon 

landslide displacement, cables are not detached from either the instrument or 

datalogger. This can usually consist of extra, free-coiled cable buried or stored near 

the instruments and dataloggers.