Geomatics
Geomatics and Remote Sensing
Manitoba Remote Sensing CentreAssessment of 1997 Flooding in the Moravia District of the Eastern Czech Republic
Hartley Pokrant and Roy Dixon Manitoba Remote Sensing Centre and MGE Data s.r.o. September, 1997 1. Background 2. Introduction - Flooding Situation 5. Field Reconnaissance and Observations 6. Discussion and Recommendations
The authors wish to thank many individuals who made this assessment trip possible and to those who provided significant support within the Czech Republic. The trip was requested and sponsored under auspices of the Canadian International Development Agency (CIDA). Many thanks to Ms Dianne Masson of CIDA for her consideration and support in making this activity possible. Logistical support and trip pre-arrangements were supplied by Mr. Robert van Wyngaarden of Geomatics International through their partner company in Prague, MGE Data. Provision of satellite image processing equipment and facilities were kindly contributed by Dr. David Strnad, President of MGE Data in Prague. While at MGE Data, Mrs. Lena Halounova provided image processing support for the RADARSAT satellite data, translation services, and field trip transportation. Mr. Svatopluk Skuta contributed many long hours in the production of map output products. Many thanks to these two individuals for their assistance and hospitality. Extensive field reconnaissance work in the flood areas was made possible through the coordination of the Povodi Moravy (Morava River Basin Authority) and the Ministry of the Environment. Special thanks to Mr. Dusan Wasserburger of Povodi Moravy who provided several days of field guiding and local knowledge within the flood disaster regions. 1.1 The Czech Republic - Description The Czech Republic (formerly known as Czechoslovakia until Slovakia recently became an independent state) is a land of 10 million people. The country occupies a land area the same size as southern Manitoba and by comparison is from Gimli to the USA border in a north/south direction and from the Ontario to the Saskatchewan border in a east/west direction. This represents a population density 100 times greater than Manitoba. The land is characterized by rolling topography with gentle mountain ranges in the north up to 1,200 m high. Flatter agricultural plains occur in many regions and average 200 - 400 m elevation. The country is at the same latitude as Manitoba and thus shares many similar species of vegetation, forests, and agricultural crops. The climate however, is fairly mild and referred to as a continental climate with winter temperatures ranging between -10 to +10 deg. C. Snowfalls are moderate with average accumulations during winter of 1 m. The country has many thriving heavy industries, factories, and chemical plants along with a large agricultural economy. Mining and the forest industry also plays a significant role in the economy. Excellent transportation systems are found throughout the country with most rural roads being paved. The population is uniformly distributed through the country with smaller villages rarely more than a few kilometers apart. Czech's capital city, Prague, has a population of 1.3 million and is one of the most significant cultural centres in Europe boasting endless concert halls, museums, arts centres, theaters, opera houses, castles, and cathedrals. Because Prague was not bombed during WW II, its historic core dates back to the 12th century featuring narrow cobble streets with period architecture including Baroque, Gothic, Romanesque, and Renaissance. After the November revolution in 1989, ending the totalitarian regime since its changing into a Communist one in 1948 and Russian occupation in 1968, Prague opened itself to Europe and the world and it became a significant tourist attraction for people from all over the world. Surrounded by a panorama of hills, with the beautiful dominant of the Prague Castle and cathedral, Prague represents an exclusive cultural, historic and architectural jewel. 1.2 Project Background During the first half of July, 1997 the eastern part of the Czech Republic received inordinate amounts of rainfall over a very short time period. This heavy rain also affected many parts of Poland, Germany, Slovakia, and Hungary. The most serious flooding occurred within the Morava, Odra, and Opava River basins. During this time period, both the Canadian Space Agency (CSA) and the Canadian International Development Agency (CIDA) were interested in the utilization and promotion of Canadian RADARSAT satellite imagery to assist in the flood disaster assessment. CIDA was aware of the radar satellite image processing expertise and flood assessment knowledge of the Manitoba Remote Sensing Centre (MRSC) within Manitoba's Department of Natural Resources as a result of two, back-to-back serious floods in the Red River Valley during 1995 and 1996. Because CIDA was already engaged in geomatics activities within the Czech Republic, they offered further assistance to Czech officials in the flood assessment process. A request was forwarded by CIDA to the Deputy Minister of the Manitoba Department of Natural Resources (DNR) seeking participation in the project. Through an existing contract with Geomatics International of Ottawa, CIDA extended that contract to facilitate Manitoba's involvement in a flood assessment initiative. Geomatics International had an existing partnership arrangement with a geomatics firm in Prague, Czech Republic called MGE Data who provided staff from the MRSC with a base of operations, computer equipment, technical assistance, transportation and guiding through the flood disaster areas. The Canadian Space Agency had arranged for the acquisition of five RADARSAT satellite images from the flood period which were available for processing upon arrival to Prague. This report describes the activities in the Czech Republic of Hartley Pokrant and Roy Dixon of the MRSC related to satellite image processing, geomatics consulting, technology transfer, field observations, and subsequent recommendations concerning the flooded region. The trip occurred between August 13 - August 26, 1997. 2.0 Introduction - Flooding Situation During the period of July 4 - 9, 1997 precipitation of approximately 600 mm fell in the Moravia region of the Czech Republic which caused serious flooding on the Morava, Odra, and Opava river basins. River heights on the main stem of the Morava River rose between 2 - 6 m while many of its tributaries rose 1 - 4 m over very short time periods. The flooding situation destroyed many river gauging stations due to the high velocity of the water racing down steep slopes which made it difficult to determine hydrologic stream flow statistics. River flows however, far exceeded hundred year flood intervals and included discharges not experienced during any other recording periods. The rainfall originated in southern Poland and moved into the northern part of the Czech Republic in the highland reaches of the Morava River headwaters. The flood situation was worsened by a second period of extensive rains occurring between July 18 - 21, 1997. Similar rainfall amounts and river discharges prevailed during this period as occurred in earlier July. Through the Morava and Odra River regions, approximately 100 deaths were attributed to the flood. Tens of thousands of people had been evacuated in Poland and the Czech Republic and factories, roads, farmland, animal stocks, and infrastructure suffered massive damage. Estimates of flood damage have been reported to be up to ten billion dollars Canadian which is equal to 6% of the entire Czech annual budget. It will take many months to restore even basic road and rail system in the disaster areas. Much of the restoration work (especially housing and basic infrastructure) is currently being conducted by locals because a coordinated compensation program by government has yet to be announced at the time of this writing. Image analysis software produced by PCI of Toronto was brought along to MGE Data in Prague and loaded onto a Pentium 166 PC with a Windows NT operating system. This workstation was networked to large disk storage devices and a 36 inch ink-jet color plotter for hard copy map production. During the course of image analysis activities, MRSC staff worked closely with MGE Data staff in order to conduct technology transfer on specific methods and techniques for flood mapping developed by Manitoba. Various operations were performed on the satellite data to produce the necessary products. After the data was loaded from the CD-ROM's, each image had sub-areas selected of the flooded river basins in order to minimize the amount of data storage and processing. The first step in the processing is the application of a 5 X 5 filter which reduces the speckle associated with radar imagery. After filtering, the new image is geometrically corrected and registered to a general conical coordinate system of the Czech Republic called JTSK. This is accomplished by doing an image registration to a 1:50,000 scale digital vector topographic map base which was available for the region. Common points such as road intersections which can be mutually identified on both the satellite image and the digital map data are chosen as control points. MGE Data used 150 control points and calculated an affine transformation for the images of July 10th and 14th. The other RADARSAT images were registered to fit these two master images. After image registration, supervised classification is conducted to highlight the flooded areas on the image. This process involves selecting training areas of the water surfaces to generate spectral signatures for classification. Because of the generally smooth surface of water, RADARSAT beams bounce or reflect off water surfaces returning little backscatter energy to the satellite. This renders the water surfaces quite black and easy to classify. Because river floods most often contain high concentrations of turbidity, mapping flooded areas with conventional black and white aerial photography can be quite difficult due to the flat, gray tones rendered by the water bodies which make the differentiation between land and water difficult. A post classification filtering task is run on the image to again remove small clusters of classification "noise" resulting from shadow and other small, dark pixel areas. The filter matrix size can range from 5 X 5 to as high as 20 X 20 depending on the amount of speckle present. Larger, misclassified pixel groups are removed through a manual editing procedure where the analyst outlines classification errors which are then made into a null class. These occurrences arise from mountainous topographic shadow lay-over effects or other natural, smooth surfaces. Final hard copy map products of the various image dates were produced at a 1:50,000 scale. Vector overlays of the rivers and lakes were superimposed and printed on top of the classification results to highlight the degree of river flooding and ponding of water. The printed maps included the black and white RADARSAT photographic background image with a color overlay of the flooded area classification and a vector overlay of non-flooded river and lake outlines. Map products were printed on MGE Data's HP 750 ink-jet plotter. RADARSAT standard beam data was acquired for various image dates to cover the flooded areas as listed below:
Upon completion of the RADARSAT satellite image processing, several meetings were held with representatives of various agencies including the Ministry of Environment, the Czech Hydrometeorological Institute, the Water Research Institute, and the Morava River Watershed Management agency. The purpose of these meetings was to review the satellite data output products, discuss utilization and integration of the products in follow-up flood evaluation. Five meetings were held in Prague, Brno and Shumperk. In all locations, presentations related to the Manitoba Land Related Information System (MLRIS) were also conducted. Approximately 100 people attended these meetings from the various participating agencies. During the course of these presentations, most of the staff were very interested in the results of the satellite data processing but it was obvious that additional follow-up will be required in order to have the radar satellite products properly integrated into a decision support system. This is largely due to the fact that these organizations have never worked with radar satellite products in the past. Many practical uses of the satellite data products were identified for their importance in the flood assessment. These uses include multi date flood boundary identification, impact assessment of rural farm land and urban areas, identification of potential mud slide areas, insurance/compensation assessment and claim verification, assessment of transportation routes available for future flood preparedness, and determination of natural resource degradation. Through the course of activities within the Czech Republic, it was noted that there are a wide range of high quality geomatics products available for the whole country including detailed topographic maps at various scales, geological maps, cadastral information, soils maps, hydrologic maps, etc. Many of these products were produced through military efforts while others are compiled through government organizations. While there is an abundance of information products available for use in a decision support capacity (such as this flood and future follow-up), three problems exist which restrict or hinder their proper utilization. There is a general lack of willingness to share the products between agencies who produce them due to perceived ownership philosophies. There is no integrated clearing house or cataloguing system in place to readily identify what products are available and where to get them from. Thirdly, there is no established distribution facility or data warehouse which gathers all available information in a unified fashion and established prices and data distribution policies. 5.0 Field Reconnaissance and Observations Three distinctive and unique flood zones occurred in the Moravia region of the Czech republic which were extensively toured and assessed over a three day period. 5.1 The Highland Region
The first region occurs in the highlands of the northern Czech
republic; the headwaters of the Morava river, at the Polish border.
This region (map location "A" - Fig. 1) has elevations of
1,200 m and has a characteristic dendritic stream pattern of
countless tributaries in deep incised valleys leading into the main
stem of the Morava River. Each valley floor is approximately one
half to one km wide with relatively steep valley sides rising
hundreds of meters high. Each of these valley floors typically has
continuous, narrow strip villages built very closely along the river
channel (see Fig. 2) with a main road and usually a railway line
adjacent to the river. Figure 2. Typical narrow strip village in the highland region of Morava River headwaters These steep valleys drop in elevation very rapidly from 1,200 m
to 200 m in a distance of only 40 km.! This gradient resulted in the
most serious damage and loss of life due to the swift moving water
flows. During the periods of heavy rainfall (600mm in 5 days) water
ran from all sides of the valleys into the smaller tributaries which
could not handle the flows. Most of these valleys were flooded
across the entire floor of the valley by 2 -3 meters of water. The
valley floor is largely made of highly erodible alluvial deposits
which resulted in undermined roads (Fig. 3), rail beds (Fig. 4), and
house foundations (Fig. 5). Serious stream channelization also
occurred in many reaches of the tributaries which created new water
courses through the easily erodible valley floors. Some attempts are
being made to force the rivers back into their original channels
through excavation and earth works projects. Many meanders in the
stream channels were shortened and straightened by the force of the
water. Unless these situations are corrected, the hydrologic flow
volumes will become even more problematic in any future flood
events. Figure 3. Serous undermining and erosion of paved road and streambed
Figure 4. Damage to railway infrastructure from swift run-off of water
Figure 5. Stream channelization and erosion caused undermining of most homes and businesses built too close to the river channel The water came with such force that people either could not move fast enough to higher ground or could not believe the seriousness of the situation. Many people actually had to climb onto house roofs to escape which accounted for many deaths as they were occasionally swept away or the home was destroyed by the swift water. A main problem in these valley regions was a total breakdown in communications. Only rudimentary phone service is available in many of these towns and villages and most of that service was cut off by the flood damage. No early warning system or emergency evacuation plans were in place to deal with a situation of this magnitude. The amplitude of the destructive force of the flood water is best
illustrated in Fig. 6 and Fig. 7. Figure 6 shows sections of river
retaining walls weighing many tonnes which were washed away or
collapsed. Figure 7 shows a solid concrete bridge two meters thick
which was torn from its moorings and swept aside. This same picture
also reveals one of the main problems associated with high damage
and mortality rates; namely, residential complexes (such as the
apartment blocks) are built too close to the river channel and are
easily undermined. Figure 6. Damage to large concrete retaining walls along headwater channel of Morava River
Figure 7. Destructive power of water velocity demonstrated by collapse of large concrete bridge Flood-proofing in these highland valleys beyond 100 year flood
events would be difficult and in many cases impractical. Even much
larger lateral river dyking would not have constrained a flood of
this magnitude because it came down the valleys from all sides,
destroying entire valley floors (Fig. 8). Due to heavy population
concentrations in the valley basins, construction of retention
reservoirs would necessitate the moving of built-up areas, roads,
and railways. Considering the steep topography, reservoir storage
capacities would be small and in most cases, front walls of the
reservoirs would have to be very high. Because of the large number
of tributaries feeding the Morava River in the highland region,
individual reservoirs would restrain only small amounts of the
catchment run-off waters. Figure 8. Example of entire valley floor washed away with heavy deposits left behind 5.2 The Lower Flood Plain Region The lower flood plain of the Morava River starts north of the
town of Olomouc (map location "B" Fig. 1). This region is
characterized by rolling plains and flat agricultural lands.
Photograph (Fig. 9) shows the origin of the flood plain looking back
(northward) towards the upland headwaters of the Morava River.
Throughout this flood plain area, many large towns are located along
or near the Morava River channel. Many large communities were
inundated by the spreading flood waters as they moved down from the
highlands including the towns of Litovel, Olomouc, Troubky,
Kromeriz, and Otrokovice. Most of the flood waters were between 1 -
2 meters in depth though the towns, and deeper nearer the river
channel. Figure 9. Transition area from floodplain looking back (north) towards Morava River highlands Flood protection through the communities is typically lateral river dykes offering protection to the 100 year flood level. While ring dyke protection for most of these communities would be a feasible and practical solution, none were found to exist in these towns likely due to the fact that floods of this magnitude were not common for the region. Even though the water velocity was considerably less than in the
highland regions, the degree of damages and number of homes and
business establishments impacted was worse considering higher
population numbers in the larger towns. The town of Troubky (near
the Morava River), was totally under water at a depth of 1.5 - 2
meters. This town could be considered largely destroyed. Most houses
in the Czech Republic are built from large, square terracotta blocks
with stucco applications over top on the interior and exterior.
Unfortunately, most of the homes in this town were built from
air-dried clay blocks rather than kiln fired block. The result was
that most of the homes literally "dissolved" like sugar
cubes from standing in water for over a week (Fig. 10). Figure 10. Damaged houses in the town of Troubky near Morava River Typically, homes in the countryside and towns within the flood plain are made of heavy fired clay block rather than wood frame construction as is more common in North American homes. Because of this heavy construction process, the majority of the homes in the flood plain towns survived structurally because the water velocity was also much less than in the highland towns. However, these homes experienced severe internal damage from mud siltation and standing in water for a week or more. Many thousand dwellings were affected like this. The potential exists for many serious environmental impacts as a result of flooding over sewage treatment plants, chemical factories, waste sites, livestock operations, and fuel storage facilities. 5.3 The Landslide Region In the area of Vsetin, map location "C", Fig. 1, (south
eastern Czech - along the Becva River) large amounts of rainfall
also hit this region. The Vsetin area is highland country with many
valleys similar to the headwaters of the Morava River. While
flooding and associated damages were typical of the Morava district,
the main concern was mud slides. The steep topography in this hilly
region is overlain with 1 - 2 meters of shales and organic soils
over a clay base. During the period of heavy rainfall, high
concentrations of water percolated through the porous upper soil
zone to the impervious clay layer. This process in effect,
"greased" the underlaying clay layer of the steeper slopes
which resulted in many catastrophic mud slides along with more
gradual movement of large soil masses down the mountain faces. These
mud slides were observed on both forested and cleared slopes used
for agriculture. Figure 11. Block house under construction being consumed by mud slide In a village near Vsetin, a large mud slide measuring 1.5 km in
length and 1 km wide is moving down the mountain side and is
threatening to consume a large portion of that village. Figure 11
shows this mud slide having consumed the back yard of a new home
which was under construction. Note that the entire mountain face has
already moved tight against the back wall of the house. The clay
block construction is typical of most homes built in the country. A
further view looking down from the top of the mud slide to the
valley below (Fig. 12), shows that a large cemetery on the middle of
the slide is also moving down the mountain side. During the period
of heavy rainfall, this landmass moved up to 7 meters in one day.
Currently, it is moving at a rate of 10 cm per day. Within a short
time period, this slide may consume a section of the town and pinch
off the river below. Government officials have had to relocate
affected families and provide new and safer building locations. Figure 12. View from top of mud slide moving down to valley below Within a neighboring village, a large slide consumed several
homes along a street, continued on down the slope and filled the
river channel causing serious back flooding (Fig. 13). There were
more than 50 locations where these mud slides had occurred and many
more areas where officials were concerned of the potential for more
to occur. It was obvious that the amount of damage resulting from
the mud slides, flooding erosion, and damage to infrastructure will
take several years to repair or replace. In some instances,
re-construction costs may be too high to repair some of these
damages at all. Figure 13. Mud slide which destroyed many homes, covered road, and filled river below 6.0 Discussion and Recommendations Through field observations, assessment of the RADARSAT satellite imagery, and discussions with local officials in the flood region, many post-flood issues, concerns, and opportunities were noted. The following discussion points and recommendations do not imply that these concerns and issues are not being addressed but rather, the intent is to document and inform the reader who may be unfamiliar with the flood situation. 6.1 Information Technologies/Geomatics The Czech Republic has available a wide array of high quality geomatics products in a variety of paper based and digital formats. Topographic mapping is complete for the entire country at 1:50K and 1:100K scales. Paper based cadastral and property ownership products are being converted to digital bases in order to provide the necessary information to return the once nationalized private lands back to the original owners/families. Many other data bases such as geological surveys, soils maps, forestry data, land use, and hydrological surveys also are available. It appeared that improvements could be made in the area of interagency cooperation and co-assessment of the flood damages and repair issues. In order to handle post flood remediation, flood assessment, insurance claims, and future flood proofing, a complete digital data base of the flood disaster area should be assembled for all participating agencies to share. It is recommended that the Morava Watershed Authority spearhead the development of such an integrated data base to serve as a decision support system for the future. Because of the multi disciplinary nature of managing this water resource, it is also recommended that philosophies of integrated resource management and sustainable development be promoted in the region and the necessary software tools be acquired to assist in that capacity. Two turn-key software packages have been developed and are available in Manitoba which would be of great assistance in these endeavors namely, the "Integrated Resource Management System" and the "Watershed Management System". Local officials acknowledged that data sharing between government departments and NGO's is problematic due to perceived ownership issues and attitudes, lack of distribution and pricing policies, and inadequate data cataloguing. It is therefore recommended that in order to create an efficient, effective, and economical geomatics strategy for the country, an integrated approach to a country-wide land related information system should be developed and led by government with private sector and NGO participation. Excellent information has now been assembled on the extent of flooding through the processing of the RADARSAT satellite image products. This data set should be promoted and distributed to officials working on the flood assessment as it documents the spatial extent of the flood for future flood proofing considerations. A technology transfer program and education/awareness program should be conducted to potential users of RADARSAT data on its uses and integration techniques with other data sets for this flood assessment and other related resource management purposes. 6.2 Flood Protection/Flood Proofing Measures Few enhanced flood protection opportunities within the highland headwaters of the Morava River are available to protect against catastrophic events as occurred during the 1997 precipitation event. The high concentration of dendritic tributaries collectively contribute to a large water catchment area. Construction of small retention reservoirs may help smaller local valleys but at the expense of relocating infrastructure and housing in many instances. A risk management study should be conducted to determine the probability and frequency of such a rare flood event in the future to determine if significant flood protection measures are economically feasible for the level of risk involved. It is recommended that a hydrological engineering study be conducted on the options for further flood proofing in the highlands. Lateral river dykes should be reinforced and raised to at least the 100 year flood event. The study should also include a full risk management and feasibility evaluation to determine the costs required to cover a specific risk such as the recent and rare heavy rainfall event. In order to mitigate future loss of life, it is recommended that early warning systems be installed in these highland river valleys such as loud sirens triggered by river float bobbers which would automatically activate the sirenes with a rise in a predetermined dangerous river level or velocity. Coupled with an early warning system, emergency evacuation plans should be set in place to move inhabitants to safer ground during flood threats. Emergency communications systems should also be enhanced. Downstream flood plain communities only have lateral river dykes to the 100 year flood level which offered little protection when the river left its banks and enveloped these towns. Based on the water depths which occurred in most of these downstream flood plain communities, it is likely that a process of constructing ring dykes around the built-up areas would be practical and economically viable when weighed against the tremendous loss incurred without this protection. It is recommended that engineering surveys should be conducted to evaluate the potential for ring dyke protection of these flood plain communities. 6.3 Ecological And Environmental Issues The magnitude of the damage due to stream bed erosion and infrastructure has created a situation where remediation is being conducted as fast as possible in order to restore basic services. Unfortunately, it is difficult for officials to coordinate all of these activities, many of which are being done on an ad hoc basis, to proper standards. The following areas should command the most immediate attention:
6.4 Building Codes And Compliance In most of the highland communities, many roads, railways, and especially homes have been located far too close to the stream channel and are easily undermined from erosion and weight stresses on the banks. Near stream development also encourages removal of native vegetation and encourages added run-off pressures. It is recommended that a thorough review of building codes and zoning be conducted to evaluate the current building practices in light of this recent flood event. Homes now too close to the stream beds which are being undermined should be identified and considered for relocation. 6.5 Reconstruction And Assistance Opportunities At the time of the field visit, it was observed that significant damage restoration was being conducted by locals within the area. Great determination was shown on the part of homeowners and businesses to restore their structures and lifestyles. These efforts should be coordinated with an integrated restoration plan to maximize the labor and equipment resources within the region. Many countries have expressed a desire to provide financial and/or direct aid to the flood region as soon as the necessary information is made available from government officials regarding specific needs. Because of the magnitude of the damage, it is recommended that most of the restoration efforts should be directed to the restoration of family homes rather than large infrastructure projects. This is what will mean the most to the community. It is also suggested that a larger labor pool could be made available through the utilization of the unemployed or those people on social assistance. Regional Czech officials should compile a central directory of specific aid and assistance requirements and post these as soon as possible with foreign embassies. 6.6 Mud Slide Region Issues Within the mud slide region, it is very unpredictable where these slides may occur as noted by the fact that they were common on both forested and agricultural slopes. Many homes were identified as being threatened or already damaged. It is recommended that a project be undertaken to create a GIS base of information including a digital terrain model, slope information, soil survey mapping, land use, building locations, and inventory of current slide locations. This data base could be used to model locations where future slides may occur. Land development and zoning policies should be reviewed for those areas where current slides are prevelant. A program of home relocation should be considered where the safety of families are compromised. 6.7 Compensation At the time of writing, the Czech government was still developing its compensation package for flood relief victims for reconstruction. Most families did not have insurance coverage for flood related damages. Government assistance is being provided in the areas of shelter, food, and clothing, along with some nominal funds for infrastructure and renovation work. It is recommended that if Czech officials wish to develop a comprehensive aid package, that they could consider consulting with Manitoba Provincial and Federal officials on strategies used for a similar situation in Manitoba. Consideration should be given to the many advantages that geographic information system (GIS) technologies could play in the process of administrating a financial compensation package. The GIS could be used in conjunction with a data base and map base to depict all impacted facilities, to administer mail-outs and information distribution, and to model equitable distribution of funds relative to population and regional damage variation.
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Figure 1. Location Country Map 
