Report on consulting services for the creation of a ...coastal-protection-mekongdelta.com/...geodatabase_estimation_coastline... · Report on consulting services for ... security

Report on consulting services for

the creation of a coastal area related geodatabase including processed historical

maps from French archives as well as recent GIS material and the estimation of

coastline regression since 1904 in the southern Mekong Delta

by Roman Sorgenfrei

Geodata Management Advisor

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Contents 1. Introduction ................................................................................................................................................... 2

2. Collection of historical maps .......................................................................................................................... 3

2.1. Processing of historical maps from the French colonial archives and map series L7014 ...................... 4

2.2. Limitations ............................................................................................................................................. 5

3. Google Earth satellite images ........................................................................................................................ 5

3.1. Recent images ....................................................................................................................................... 5

3.2. Time series – historical satellite images ................................................................................................ 6

3.3. Note about users licence for Google Earth imagery .............................................................................. 6

4. Geodata collection of already available data from GIZ offices ...................................................................... 7

5. Shoreline change analyses ............................................................................................................................. 8

5.1. Shoreline change rates (DSAS) .............................................................................................................. 8

5.2. Notes ................................................................................................................................................... 10

5.3. DSAS – Results ..................................................................................................................................... 11

5.4. Shoreline area changes ....................................................................................................................... 16

6. Conclusion and recommendations ............................................................................................................... 20

Paths of stored data and structure ....................................................................................................................... 21

References ............................................................................................................................................................ 24

Appendices ............................................................................................................................................................ 26

Appendix I – Historical maps collection - 1904 .................................................................................................. 26

Appendix II – Historical maps collection - 1924 ................................................................................................. 27

Appendix III – Historical maps collection - 1953 ................................................................................................ 28

Appendix VI – Historical maps collection - map series L7014............................................................................ 29

Appendix V – Google Earth Satellite Images - recent images (2014 & 2015) ................................................... 30

Appendix VI – Google Earth Satellite images - recent images (folders) ............................................................ 31

Appendix VII – Google Earth Satellite Images - time series (folders) ................................................................ 31

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1. Introduction

Funded by the governments of Viet Nam, Germany and Australia the Integrated Coastal Management

Programme (ICMP) is a development programme implemented by the Deutsche Gesellschaft für

Internationale Zusammenarbeit (GIZ). To support the Vietnamese authorities in preparing the coastal

area of the Mekong Delta for a changing environment as well as to lie the foundations for sustainable

growth are its objectives.

One component of ICMP is the task team Coastal Protection. Its focus lies on the stabilisation and

security of the coastline of the southern Mekong Delta. This shall be achieved with the development

of an Integrated Coastal Protection Plan for the southern Mekong Delta. Important pillars of this

programme component are the restoration of the foreshore area, coastal engineering measures to

enhance natural processes and the planning of sea-dykes based on local circumstances. The mangrove

belt along the coast plays a significant role in securing the residents and livelihoods in coastal areas.

Therefore the rehabilitation of mangroves is an essential part of coastal protection. ICMP supports

provinces and institutions in the development and application of science-based instruments with the

aim of finding the best appropriate and effective measures for coastal protection investments.

To understand the morphological development of coastlines, the original hydrology of coastal areas

as well as the former distribution of mangrove forests, a key tool of ICM is used, the analysis of

historical maps, aerial images, and satellite images (ALBERS et al. 2013, p. 98f.). Already in the past the

former GIZ-project “Management of Natural Resources in the Coastal Zone of Soc Trang Province”,

now part of ICMP, commissioned the creation of a historical shoreline geodatabase. It includes

historical maps from French colonial archives, aerial photos, recent satellite images, as well as digitised

land-use shape files (HNEE 2013a & 2013b). The database helps to understand historical land-use and

shoreline changes along the coast of the province and hence the planning progress of future activities.

Recently, ICMP gathered further historical maps from the French colonial archives covering the

remaining area of interest in the Mekong Delta. Additionally, it is planned to also obtain further

historical aerial photos for these regions. These historical datasets can be compared with recent

satellite images, land-use and irrigation maps. Thus, the natural and anthropogenic forces which

shaped the coast of today and which challenge the plans for the future can be better understood for

the whole programme area.

The aim for this consultancy was to combine the up to now separately stored coastal area related

geodata of the GIZ provincial offices into one categorised archive and to expand it with further

material like recent satellite images from Google Earth. The result is a digital coastal area related GIS

database which can be used as a source of maps and map contents for a Coastal Atlas of the southern

Mekong Delta. The coastal area related GIS data is available in a format which makes them usable for

various future applications.

Furthermore the collected maps and images were used to digitise the changing shorelines from 1904

till 2015. These were then used for shoreline change analyses to calculate regression and transgression

rates as well as area changes. The rates were calculated using the ArcGIS 10 extension DSAS - Digital

Shoreline Analysis System (U.S. GEOLOGICAL SURVEY 2015a).

In addition, recent data for the whole Mekong Delta from the Southern Institute of Water Resource

Planning (SIWRP) and Sub-FIPI (Institute for Forest Inventory and Planning) should have been included

into the database. Unfortunately it was not possible to get these data until now.

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2. Collection of historical maps

Of interest for coastal area related analyses are maps with a scale of at least 1/100 000. Is the scale

smaller, map contents like shoreline and hydrology are too inaccurate and often too aggregated to be

used for analyses, e.g. analysis of shoreline changes over time.

The historical maps from the French colonial archives provided by ICMP that fulfil the above

mentioned criteria are of varying quality and scale. They cover the time of the first half of the 20th

century and were published in different coordinate reference systems (CRS). Table 1 gives an overview

of the properties of these maps.

Tab. 1: Properties of historical maps suitable for coastal area related analysis provided by ICMP.

Year Scale Ellipsoid / Spheroid Datum Projection

1903/04 1/100 000 Clarke ellipsoid no datum given Bonne 1923/24 1/100 000 Clarke ellipsoid no datum given Bonne 1951 1/100 000 Clarke ellipsoid no datum given Bonne 1953 1/100 000 Everest spheroid no datum given UTM 48N

In addition to the maps provided by ICMP, topographic maps of Vietnam published by the U.S. Army

Map Service were found in the internet (UNIVERSITY OF TEXAS LIBRARIES 2015a). After the USA got more

involved into the war in Vietnam they conducted mapping campaigns and published a new map series

(L7014) for the whole of Vietnam (DANG & LE 2001). They updated the old French topographic maps

supported by several aerial photography missions and increased the scale to 1/50 000. These maps

are the most accurate and detailed scanned maps used for this compilation.

The majority of the maps from this series displaying the area of the Mekong Delta are from 1965, but

some are from later years (see Tab. 2 for their properties). Few were updated last in the year 1989,

for which no older versions are available online anymore. One map displaying a part of Phú Quốc

Island is from 1957, while the map displaying the border between Vietnam and Cambodia is from

1993. The latter is the only map from the U.S. National Imagery and Mapping Agency, Series L7015,

Cambodia Topographic Maps (UNIVERSITY OF TEXAS LIBRARIES 2015b).

Tab. 2: Topographic maps of Vietnam from U.S. Army Map Service, Series L7014 (UNIVERSITY OF TEXAS LIBRARIES 2015a).

Year Scale Spheroid Datum Projection EPSG code Quantity

1957 1/50 000 Everest Indian 1960 UTM 48N 3148 1 1965 1/50 000 Everest Indian 1960 UTM 48N 3148 31 1969 1/50 000 Everest Indian 1960 UTM 48N 3148 3 1970 1/50 000 Everest Indian 1960 UTM 48N 3148 1 1989 1/50 000 WGS 84 WGS 84 UTM 48N 32648 3 1993 1/50 000 WGS 84 WGS 84 UTM 48N 32648 1

To ensure that geodata from different sources, and in the current case especially different times, can

be analysed and compared, it is necessary to use a common coordinate reference system (CRS).

Internationally the CRS usually used to exchange geodata is the geographic coordinate system WGS

84 (EPSG: 4326). For most of the other CRS, which are usually applied in regional mappings,

transformation algorithms into WGS 84 exist. Therefore WGS 84 is the CRS to choose to make geodata

available for as many users as possible.

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2.1. Processing of historical maps from the French colonial archives and map series L7014

Unfortunately, the old maps provided by ICMP lack information about the datum of the ellipsoid and

spheroid, which is necessary in order to georeference the scanned maps into their original CRS and

then transform them into WGS 84.

Therefore, the map series L7014 provided in GeoPDF format was processed first, and based on them

the older maps were georeferenced directly into WGS 84. The workflow of the georeferencing for the

map series L7014 is shown in table 3.

Tab. 3: Workflow for georeferencing map series L7014.

Processing step Example resulting file name

1 Download GeoPDF from UNIVERSITY OF TEXAS LIBRARIES 2015a tra_cu-6228-2.pdf 2 Save as Tiff file format using Adobe Photoshop tra_cu-6228-2.tif 3 Georeference into Indian 1960/UTM 48N or WGS84/UTM 48N,

depending on original CRS (see Tab. 2) using ESRI ArcGIS (define CRS to the Tiff files in ArcCatalog before using them in ArcGIS; transformation type ‘Adjust’; compression type ‘LZW’)

tra_cu-6228-2_.tif

4 Transform into WGS 84 using ESRI ArcGIS tool ‘Project Raster’ (transformation technique 2)

tra_cu-6228-2_WGS84.tif

5 Clip the surrounding borders (frame and legend) of the GeoTiff files (ArcToolbox -> Data Management Tools -> Raster -> Raster Processing -> Clip)

tra_cu-6228-2_WGS84_Clip.tif

The historical maps from the French colonial archives were georeferenced using QGIS. As reference

the maps from series L7014 were used in combination with Google Maps Satellite Images (OpenLayers

plugin for QGIS). When using the satellite images from Google the projects CRS in QGIS is automatically

set to WGS 84 / Pseudo Mercator (EPSG: 3857) and the additionally loaded map series L7014 is

automatically projected into the same CRS. Therefore the georeferencing results of the historical maps

from the French colonial archives were also in WGS 84 / Pseudo Mercator and had to be transformed

into WGS 84 with ESRI ArcGIS (see Tab. 4 for the workflow).

Tab. 4: Workflow georeferencing the historical maps from the French colonial archives.

Processing step Example resulting file name

1 Open .JP2 files and save them as tiff files (Adobe Photoshop) 237_100K_1904.tif 2 Crop maps to delete parts showing open sea (Photoshop) 237_100K_1904_.tif 3 Enhance imagery in Photoshop (colour, tone and saturation) 237_100K_1904__.tif 4 Georeferencing in QGIS based on map series L7014, file name

indicates the transformation type (Thin Plate Spline) and the number of ground control points (GCPs) used

237_100K_1904_TPS19.tif TPS = Thin Plate Spline 19 = number of GCPs

5 Transform into WGS 84 using ESRI ArcGIS 237_100K_1904_TPS19_WGS84.tif

The ground control points (GCPs) created for the georeferencing were saved as .points files (e.g.

237_100K_1904_GCP19.points). Therefore, the already cropped images (result step 2 in Tab. 4) can

be further enhanced in Adobe Photoshop if needed and then georeferenced again with a few clicks in

QGIS, as long as they are not cropped any further. Between 19 and 61 GCP were used to georeference

each map with a focus of the points in the coastal areas.

All historical maps which were georeferenced are now available in WGS 84. The Appendices I to IV

give an overview of the historical maps that were georeferenced. Before publishing they should be

projected into UTM 48N (WGS 84 / UTM 48N = EPSG: 32648).

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The georeferencing results of the historical maps are stored in the path

…\Coastal_Area_GIS_database\historical_maps\

Further details about the file system of the Coastal Area GIS database can be found on page 21.

Beside of the historical maps showing Ben Tre (236_100K_1903.tif and 236_100K_1953.tif) all

available maps from the French colonial archives were processed. Additionally, there are further

georeferenced historical maps covering Soc Trang Province. They are stored in the shoreline

geodatabase of Soc Trang Province created by Eberswalde University for Sustainable Development in

2013 (HNEE 2013a & 2013b).

2.2. Limitations

It needs to be mentioned that the map series L7014 is the most accurate in all terms. In comparison

to the older maps in particular the hydrological information is more accurate. In this regard especially

the maps from 1953 need to be handled carefully, because they suggest accuracy due to their detailed

content, but the georeferencing process showed a high degree of generalisation for the hydrological

map content.

The coastal areas, especially the coastline itself, between the map borders close to the border of Kien

Giang Province and Ca Mau Province, need to be considered inaccurate for all maps from the French

colonial archives (see Appendices I, II and III, between map tiles Kien Giang and Ca Mau West). The

same is the case for the maps from 1953 between the map tiles Ca Mau West and Ca Mau South (see

Appendix III).

3. Google Earth satellite images

The Google servers store a big collection of satellite images for the Mekong Delta region ranging for

some parts from the year 2000 till 2015 and are still getting updated. These images give good, and in

latest years also in high resolution, information about the development of the coastal areas. Still they

have to be treated carefully since their georeferencing is not always accurate (offsets of around 20 m

are possible). In comparison to this, the small offsets resulting from the manual georeferencing

process of exported Google Earth images (screenshots) can be neglected.

In general, the Google Earth maps can be divided into recent satellite images, usually shown when

using the Google Earth GUI, and the historical satellite images which are provided additionally.

Because Google chooses the date of the images shown in standard view based on their date as well

as their quality (e.g. cloud cover), some of the satellite images available in the timeline view are from

a more recent date than the usually shown ones.

The images from Google Earth are coming from two suppliers which hold the copyrights. For images

until the year 2013 this is DigitalGlobe, while the images since 2014 are from CNES/Astrium.

3.1. Recent images

The recent satellite images can be downloaded directly from the Google servers using the software

‘Google Satellite Maps Downloader’. It loads all the tiles stored for a chosen rectangular extend from

the Google servers and provides an option to combine the tiles into a single BMP file, which is already

georeferenced (CRS = WGS 84, EPSG: 4326). First, the bounding boxes coordinates were extracted

from Google Earth (GE settings: Decimal Degrees). They define the size and location of the area to be

downloaded. The resolution (zoom) chosen for the download was 18 and is therefore a compromise

between file size and resolution. The Google Servers limit the number of direct server accesses per

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day which also limits the application of this technique. The download of the images was therefore

spread over several days. Appendix V shows the downloaded recent satellite images in overview maps.

They are stored in the following path:

…\Coastal_Area_GIS_database\GE_images\recent_images\

Further details about the file system of the Coastal Area GIS database can be found on page 21.

3.2. Time series – historical satellite images

Since the beginning of this year the software ‘Google Earth Pro’ is available for free. It offers the

possibility to export images of the chosen view in high resolution. To make georeferencing of these

images easier and faster, the view in Google Earth Pro needs to be oriented north, not tilted and the

terrain needs to be switched off to eliminate vertical exaggeration which alters the images. For the

image export the eye altitude of the view was set to 2,000 m. Each exported image has a resolution

of 4800 x 3372 pixels.

Additionally, it is necessary to place three ground control points (GCPs) in three corners of the chosen

view area. The smaller their icon, the more accurate the georeferencing can be done (scale chosen

was 0.2). After exporting the image including the GCPs, the same image was exported again but the

GCPs were deactivated. Additionally the remaining available time steps from the timeline for the

chosen view (without GCPs) were exported.

In QGIS, the first image of each image set, which includes the GCPs, needed to be georeferenced. The

chosen transformation type was ‘linear’. The necessary coordinates were read from Google Earth Pro

in the properties of the GCPs (GE settings: Degrees, Minutes, Seconds). Usually the offset (residual) of

the GCPs in QGIS will be <0.5 pixel (1 pixel = 0.5 meter). If the residuals are higher, the orientation and

terrain settings in Google Earth Pro need to be checked. Finally the GCPs from QGIS were saved into

.point files and the worldfile of the extracted image created.

The other images which do not include the GCPs in the picture, but were exported without changing

the view in between, were georeferenced by loading the former .point file into the Georeferencer tool

of QGIS and applying it for all images of an image set.

With this method the historical satellite image sets of focus areas along the coast of the Mekong Delta

were exported from Google Earth Pro and georeferenced. They are available offline now. Appendix

VII shows an overview map of the areas for which all the available satellite image sets were

downloaded.

The path in the database where these files are stored is

…\Coastal_Area_GIS_database\GE_images\time_series\

Further details about the file system of the Coastal Area GIS database can be found on page 21.

3.3. Note about users licence for Google Earth imagery

Another important point which needs to be mentioned is the limited users licence from Google Earth

satellite images in case of publishing:

“Google does not own the imagery they display in Google Earth, and so cannot give

anyone else a licence to use that imagery for any purpose other than screenshots - which

may be used unaltered in commercial reports or presentations: i.e. single, static,

ungeoreferenced images retaining full attribution to Google and its suppliers.”

(STACKEXCHANGE.COM 2014).

“(…) You can use Google Earth Pro images and data for marketing purposes as long as this

data is not sold to any third parties. Additionally, the images must retain their copyright

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and source information. Images and videos used in on-air media require special approval.”

(STACKEXCHANGE.COM 2014).

Before publishing maps with satellite images in the background provided by Google it is necessary to

clarify licence issues. For further information see GOOGLE EARTH HELP (2015) and GOOGLE PERMISSIONS

(2015).

4. Geodata collection of already available data from GIZ offices

The GIZ offices in the provinces of the Mekong Delta acquired already different amounts of geodata

in the past. The data considered relevant for a coastal area related GIS database were collected. They

contain different information, depending on the former projects activities like shapefiles from

coastline mappings or land-use classifications. The files were stored in respective subfolders

depending on the corresponding province in the path …\Coastal_Area_GIS_database\provinces\

For Bac Lieu Province the folder contains one subfolder with maps (Agricultural Plan 2020, Forest

Development 2012 and Irrigation) in MapInfo as well as shape files and one subfolder containing single

shape files like coastlines of several years.

For Ca Mau Province the geadata available until now is limited to a compilation made by Petra

Gabelmann during an internship in the year 2013. It can be found in the respective folder.

For Kien Giang Province several maps are available containing recent data about forest distribution as

well as hydrological information. Additionally, a big collection of data was included into the database,

but the data was not yet further selected according to relevance for coastal area related programme

work (only the video files of a shoreline monitoring campaign were deleted due to their file size).

For Soc Trang Province, beside of the above mentioned historical shoreline database by HNEE, several

maps like mangrove forest plantation sites and land-use 2006 were included as well as separate shape

files of coastline monitoring and T-fence locations.

In addition, recent data for the whole Mekong Delta from the Southern Institute of Water Resource

Planning (SIWRP) and Sub-FIPI (Institute for Forest Inventory and Planning) should have been included

into the database. These datasets would be the best recent information available to conduct analyses

about changes in the coastal areas of the Mekong Delta in comparison to the historical files now

compiled. Unfortunately, it was not possible to get these data until now.

It is important to mention that data from partner institutions are often only available in MapInfo

format. These files can be read and edited in QGIS, but for wider usability the data should be converted

into shape files using the build in Universal Translator tool of MapInfo. Its advantage is the possibility

to convert the format in batch mode for complete folders. If a MapInfo license is not available this

conversion into .shp can also be made using QGIS. Therefore load the MapInfo file into the Layer view,

right click on the layer and save as ESRI Shapefile. The files provided from the GIZ offices of Kien Giang

and Bac Lieu were already processed.

Users also have to be careful because files from partner institutions usually are provided in the

coordinate reference system VN 2000 and therefore still need to be transformed (be aware that VN

2000 is different for each province). This is also the case for data converted into .shp file format. Until

now there is no instruction for this transformation issue available.

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5. Shoreline change analyses

Beside the creation of a coastal area related geodatabase, the aim of this consultancy was to obtain

knowledge about historical coastal regression and transgression along the coast of the Mekong Delta.

With the now available georeferenced historical maps and satellite images it is possible to examine

the historical changes along the coast (see Fig. 1)

Fig. 1: Coastline regression from 1904 until 2014 in eastern Ca Mau Province based on georeferenced historical maps and recent satellite images.

Shoreline change rates along transects covering big parts of the Delta were calculated using the ArcGIS

10 extension DSAS - Digital Shoreline Analysis System (U.S. GEOLOGICAL SURVEY 2015a). Additionally, the

absolute area change in hectare was calculated using ArcGIS. The Mekong river island Cu Lao Dung

was excluded from the analysis because it was already analysed before.

5.1. Shoreline change rates (DSAS)

The application of DSAS is described in detail in the ‘Installation Instructions and User Guide’, available

on the website of the U.S. Geological Survey (U.S. GEOLOGICAL SURVEY 2015b). In addition, MADORE 2014

provides a very good step by step manual for the complete DSAS workflow. Therefore, only a view

specific details will be presented here and not the complete workflow of the DSAS application. All files

related to the analyses of shoreline change rates are stored in the ArcGIS geodatabase

‘shorelines_mekong_delta.mdb’ stored under …\Coastal_Area_GIS_database\DSAS\

A general dataset with a collection of shorelines spanning the whole available time from 1903/04 till

2014/2015 and covering the complete Mekong Delta was created first for overview analyses.

Therefore the shorelines of the georeferenced historical maps from 1903/04, 1951/53 and the map

series L7014 were digitised. The maps from 1923/24 only differ from the 1903/04 maps in their areal

information like land use and hydrology, but have exactly the same shoreline as the older maps.

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Consequently, they were not digitised and excluded from analyses. In addition, the shorelines, defined

as the seaward vegetation border, of the recent Google Earth satellite images were digitised. All

digitisations were made in clockwise direction, which simplifies the use of several tools of ArcGIS.

For in depth analysis of several focus areas the additionally available historical satellite images from

Google Earth were also digitised and further expanded with already available shorelines from

shoreline monitoring surveys done by GIZ projects in Bac Lieu and Soc Trang as well as further digitised

historical maps from the Soc Trang geodatabase (HNEE 2013a).

Tab. 1 shows a list of all collected shorelines with their date and source. In total 70 shorelines were

collected and combined into the Feature Class ‘shorelines_all’.

Tab. 5: List of all collected and digitised shorelines.

The DSAS requires that the date is always given in a 10 digit code, e.g. 23/03/2011 (U.S. GEOLOGICAL

SURVEY 2015b). Therefore the dates of shorelines representing not a specific date but a year, as it is

the case for all the digitised maps as well as the GPS shoreline surveys from Bac Lieu, were set to the

1st of July of the corresponding year (see Tab. 5).

The baselines were cast along the coast of the whole Mekong Delta, mixed on- and offshore. For the

analysis of the whole delta a distance of 100 m between each transect was chosen, while the distance

was 50 m in the focus areas. For the focus area examination the baselines were altered to better follow

the chosen shorelines.

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At least two shorelines from different time steps are necessary to calculate change rates with the

DSAS, which offers several statistical calculation methods (U.S. GEOLOGICAL SURVEY 2015b). The most

frequent cited methods are EPR (end point rate) and LRR (linear regression) (THI et al. 2014). This is

because they are the least expecting for the data input. The EPR is calculated by dividing the distance

of shoreline movement by the time elapsed between the oldest and the most recent shoreline in

a given data set. Its major advantages are the ease of computation and minimal requirement of

only two shoreline dates. The major disadvantage is that in cases where more data are available,

the additional information is ignored (U.S. GEOLOGICAL SURVEY 2015b). This method was used for the

overview shoreline change rates between the data from map series L7014 and the most recent Google

Earth satellite images from 2014/15.

The LRR is the result of estimating the average rate of change using a number of shoreline positions

over time, with the change statistic of fitting a least-squared regression line to all shoreline points for

each transect. The linear regression rate is the slope of the line (THI et al. 2014). This method uses all

available data regardless of changes in trend or accuracy and is easy to employ. But it is susceptible

for outliers and tends to underestimate the rate of change relative to other statistics, like EPR

(U.S. GEOLOGICAL SURVEY 2015b). This method was used when more than two shorelines were available,

like in change rates from 1903/04 till 2014/15 as well as in analyses of focus areas. The calculation was

also commuted for the change rates from 1965 till 2014/15 for comparison with the EPR results. In

total 24 EPR and LRR calculations were made for varying areal and temporal extends.

5.2. Notes

While it is not possible to allocate values of accuracy for the old historical maps, it would be possible

for the Google Earth satellite images as well as for the map series L7014. Because of this, and because

both used calculation methods don’t use accuracy information during calculation, the accuracies of

the single shorelines were not taken into account in the conducted analyses. For further analyses of

the more recent data, for which accuracy can be allocated, other statistical methods like weighted

linear regression (WLR), can be used (U.S. GEOLOGICAL SURVEY 2015b).

Because the digitised shorelines from 1903/04 and 1951/53 are less accurate than the more recent

ones from the map series L7014 and Google Earth satellite images, the results calculated with them

need to be handled with caution. They are less exact than the results from the later shorelines and

can therefore only show a general trend for the shoreline movement.

Further satellite images to close the gap between the historical maps from 1965 and recent satellite

images exported from Google Earth can be obtained online (U.S. GEOLOGICAL SURVEY 2015c and GFIO

2015).

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5.3. DSAS – Results

The results of the DSAS are stored as maps in JPG and PDF file format are stored under

…\Coastal_Area_GIS_database\DSAS\_map_output

The corresponding ArcGIS 10.3 ArcMap document files have the same name like the exported maps

and are stored in the folder …\Coastal_Area_GIS_database\DSAS\

The advantage of the PDF files is the possibility to use the zoom function in which the vector data can

still be seen in detail, while the JPG files have resolution limitations.

Several calculation results based on the four main shoreline sets from 1903/04, 1951/53, L7014 (1965-

1993) and 2014/15 are presented in maps showing the whole Mekong Delta and southern Ca Mau:

DSAS_1904_2015 (DSAS_1904_2015_incl_transects) [using LRR]

DSAS_1965_2015 (…_incl_transects) [using EPR]

DSAS_MuiCaMau_EPR_1904_12015 (…_incl_transects)

DSAS_MuiCaMau_EPR_1965_2015 (…_incl_transects)

DSAS_MuiCaMau_LRR_1904_2015 (…_incl_transects)

DSAS_MuiCaMau_LRR_1904_2015_accretion (…_incl_transects)

DSAS_MuiCaMau_LRR_1904_2015_accretion_old (…_incl_transects)

Example maps are shown below in Fig. 2 and Fig. 3 for the LRR and EPR results of southern Ca Mau.

Fig. 2: Map ‘DSAS_MuiCaMau_LRR_1904_2015’ showing shoreline regression rates on the east coast and shoreline

transgression rates on the west coast of southern Ca Mau from 1903/04 till 2014/15.

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Fig. 3: Map ‘DSAS_MuiCaMau_EPR_1965_2015’ showing shoreline regression rates on the east coast and shoreline

transgression rates on the west coast of southern Ca Mau from 1965 till 2014/15.

For the following focus areas change rates were calculated including all available shorelines of the

examined area except for the ones labelled as unknown source and unknown definition in Tab. 5:

Border between the provinces Bac Lieu and Soc Trang (DSAS_FOCUS_BL_ST_...)

Border between the provinces Ca Mau and Bac Lieu (DSAS_FOCUS_CM_BL_...)

Along part of the coast of Kien Giang and Ca Mau (DSAS_FOCUS_KG_CM_...)

Nam Thai A Community in Kien Giang Province (DSAS_FOCUS_KG_NamThaiA_...)

Vinh Hai Region in Soc Trang Province (DSAS_FOCUS_ST_VinhHai_...)

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Exemplarily, Fig. 4 shows the results of the focus area Vinh Hai Region in Soc Trang Province with

regression rates of up to 25 m/yr and transgression rates of up to 83 m/yr from 2006 until 2015.

Fig. 4: Map ‘DSAS_FOCUS_ST_VinhHai_2006_20015_EPR_sat’ showing shoreline transgression and regression rates from 2006 till 2015 in Vinh Hai Region, Soc Trang Province.

Like mentioned before the conducted analyses are limited due to their areal extend. Even though for

the focus areas many extra shorelines were digitised based on Google Earth satellite images, these

timelines are discontinuous for long coastal stretches. This is exemplarily the case for the focus area

along the west coast of the provinces Ca Mau and Kien Giang. The discontinuity makes it difficult to

use LRR, even for parts of the coast where many shorelines are available. Consequently, the smaller

the examined area, the better the full potential of the DSAS can be used. Therefore it is recommended

to conduct further analyses of specific sites of interest with at most 15 km of coastline using the DSAS.

This would improve the results, for example at the erosion site in Ho Be Community, Vinh Hai Region,

Soc Trang Province (visible in the centre of Fig. 4). Additionally, the results could be better presented

in exported maps, especially when using JPG file format.

On the following pages the results for the west coast are presented. While it was possible to calculate

the change rates with LRR from 1965 till 2015 (see Fig. 5), for the recent shoreline change rates

calculated solely from satellite images based shorelines, only EPR could be used (see Fig. 6).

14

Fig. 5: Map ‘DSAS_FOCUS_KG_CM_1965_2015_LRR’ showing transgression rates of up to 52 m/yr and regression rates of

up to 10 m/yr from 1965 till 2015 along the west coast of the Mekong Delta.

15

Fig. 6: Map ‘DSAS_FOCUS_KG_CM_2001_2015_EPR’ showing transgression rates of up to 70 m/yr and regression rates of

up 32 m/yr between 2001 and 2015. But not along the whole coast the time spectrum of the shorelines is complete.

16

One focus area, which was completely excluded from the

analyses presented here, is the island Cu Lao Dung in Soc

Trang Province. A separate digital analysis about

shoreline change on this island was already carried out

by the author for the GIZ project ‘Management of

Natural Resources in the Coastal Zone of Soc Trang

Province’ using the shorelines from the historical

topographic maps from 1904 and 1965 as well as IKONOS

satellite images from 2012, all prepared by HNEE. For this

analysis, the coastline was defined as being the seaward

mangrove forest edge.

The main findings of the analysis are presented in the

map in Fig. 7 and were also published in SCHMITT & ALBERS

(2014). On Cu Lao Dung Island accretion rates are ranging

from 6.2 to 68.2 m per year over a period of 108 years

5.4. Shoreline area changes

For the calculation of the areal changes the collection of shorelines was used as well. Instead of using

the complete available dataset, only the three main sources were used, 1903/04, L7014 and 2014/15.

The shorelines were divided into three areas to simplify analysis and the presentation of the data. The

three areas in which the Mekong Delta was divided are Bac Lieu / Soc Trang, Kien Giang / Ca Mau and

southern Ca Mau. The northern part of Kien Giang Province, the island Cu Lao Dung in Soc Trang

Province as well as the provinces Tra Vinh and Ben Tre were not included in the analysis.

Before interpreting the results, it is necessary to mention that the coastline of 1903/04 is not very

accurate, while trustworthy results represent the numbers for the areal changes between map series

L7014 and 2014/15. Because of this, only for southern Ca Mau the areal change between 1903/04 and

1965 was calculated.

The working process includes the transformation of the polylines into polygons using the tool ‘Feature

to Polygon’ in the ArcToolbox. In the resulting shapefile all polygons smaller than 500 m2 (0.05 ha)

were deleted and the remaining ones used to calculate the areal changes. Each polygon was classified

manually into erosion and accretion. Out of these, only the biggest polygons were labelled with their

change values in the result maps.

The results of the areal change analysis are stored as maps in JPG and PDF file format in the folder

…\Coastal_Area_GIS_database\DSAS\_map_output

The corresponding ArcGIS 10.3 ArcMap document files have the same name like the exported maps

and are stored in the folder …\Coastal_Area_GIS_database\DSAS\

The same folder also contains the ArcGIS geodatabase ‘area_changes_mekong_delta.mdb’, which

holds all relevant data.

Fig. 7: Shoreline changes on Cu Lao Dung from 1904 till 2012. Base map provided by ESRI: DigitalGlobe 2008 & 2011, GeoEye 2000 & 2009 and i-cubed 1999 (own map, also published in SCHMITT & ALBERS 2014).

17

Maps

Here comes more text about the maps

18

19

The results of the calculations in hectare are shown in Tab. 6. While along the coasts of Bac Lieu / Soc

Trang and the west coast of Kien Giang /Ca Mau the transgression exceeded the regression from 1965

until 2015, more area was eroded than accumulated in southern Ca Mau. In total, 811 ha were

accreted along the examined coast of the Mekong Delta within 49 years. This figure would be even

higher if Cu Lao Dung and the other areas excluded from the analysis were to be included (see change

rates in these areas in the overview map on the cover of this report).

Tab. 6: Transgression and regression along the coast of the Mekong Delta provinces from 1965 till 2015 in ha.

maps transgression regression Sum

Bac Lieu / Soc Trang +3,005 -1,669 +1,336 Kien Giang / Ca Mau +2,349 -763 +1,586 Southern Ca Mau +10,540 -12,651 -2,111

Sum +15,893 -15,082 +811

The second map on the cover of this report includes the areal changes from 1904 until 1965 in

southern Ca Mau. Even though the results need to be handled with caution, it can be stated that the

total area lost within the last 49 years was almost half of the lost area within the 61 years before.

20

6. Conclusion and recommendations

The now available coastal area related GIS database contains a collection of georeferenced historical

maps from the French colonial archives, online sources and recent satellite image sets of the coastal

areas of the Mekong Delta. In addition, already digitised geodata from the provincial GIZ offices is

included.

The database therefore contains the material that is necessary to compile historical maps for a Coastal

Atlas of the Mekong Delta. However, the recent material, necessary for comparisons and analyses

about various developments in the coastal areas, still needs to be extended. To mention are especially

the recent data for the whole Mekong Delta from the Southern Institute of Water Resource Planning

(SIWRP) and Sub-FIPI (Institute for Forest Inventory and Planning). They should be included into the

database, because the data is necessary for comparisons and analyses with the now available

historical data.

Additionally, it is recommended to obtain further historical material or satellite images that close the

gap between the maps from 1965 and the recent satellite images from Google Earth. That applies for

the whole Mekong Delta area, including the historical shoreline database of Soc Trang Province.

Before maps containing satellite images exported from Google Earth are published, the licence issues

need to be addressed.

Furthermore, the MapInfo files seem to be in VN 2000 and therefore need to be transformed before

they can be used together with the other data now available (see chapter 4). The cooperation between

ICMP and Can Tho University might be an option to solve this issue. Alternatively, it would be possible

to contact Mr. Trịnh Hiệp (Deputy Head, Division of Planning and Finance, Department of Agriculture

and Rural Development of Soc Trang Province). He offered his support for this issue already on

previous occasion and provided the GIZ office in Soc Trang already in the past with the necessary PRJ

file to include VN 2000 into MapInfo (older datasets have the reference system altered manually).

At last, further analyses of small, specific areas of special interest can be examined for more accurate

results of shoreline change rates, especially recent changes including accuracy information, using the

DSAS

Roman Sorgenfrei November 2015

Geodata Management Advisor

21

Paths of stored data and structure

The complete coastal area related GIS database, called ‘Coastal_Area_GIS_database’, is stored on an

external hard drive. The file ‘Index_Coastal_Area_GIS_database.html’ contains a searchable index of

the complete content of the database.

The main folders of the database contain the DSAS

analysis results, the Google Earth satellite images

(‘GE_images’), the georeferenced historical maps

(‘historical maps’), the geodata of the Mekong Delta

provinces (‘provinces’), notes about the

transformation from VN 2000 into WGS 84 and file

conversion from MapInfo into shape file

(‘VN2000_to_WGS84’) as well as a working folder

containing the original maps from the French colonial

archives and additional historic maps

(‘working_folder’).

The folder ‘DSAS’ contains the ArcGIS databases for the shoreline

analyses as well as the ArcGIS 10.3 DSAS project files. The results

of the analyses are stored in the ‘_map_output’ folder. The

‘borders’ folder contains the administrative boundaries and

background literature as well as the ArcGIS DSAS software are

stored in the respective folders.

The ‘historical_maps’ folder contains several GIS project

files named ‘collection_historical_maps_all’ (for QGIS and

ArcGIS versions 9.3, 10.0 and 10.1) and a kmz file

container for Google Earth. The latter can be used in

Google Earth to get a fast overview of which maps are

available and the paths in which they are stored. The

‘_index’ folder contains index shapefiles while the

‘_map_output’ folder contains project files for several

maps in ArcGIS. The final results of the georeferencing of

the historical maps from the French colonial archives and

of map series L7014 is in the folder ‘WGS84’, sorted into

subfolders named after the year of the published maps

and their original CRS.

22

The folders containing the Google Earth satellite

images (‘recent_images’ and ‘time_series’) contain

similar additional material like the folder of the

historical maps (indices and maps), but the

georeferenced files were stored in subfolders

representing the part of the province they show (e.g.

BacLieuEast). The images of the time series are

further sorted into subfolders named after the date

of the satellite image (e.g. path:

…\Coastal_Area_GIS_database\GE_images\

time_series\CaMauEast\20021102\).

The geodata from the GIZ offices is stored in the

folder ‘provinces’ and is further divided into

folders for each province.

The maps which were provided in MapInfo file

format were saved under ‘[PROVINCE]_maps’

and the corresponding subfolders ‘MapInfo’ and

‘SHP’, the latter containing the converted shape

files.

The historical shoreline database of Soc Trang

Province can be found in the folder

‘CZMST_GIZ_HNEE_2013’.

The working folders contain the files for the single steps described above for the georeferencing of

the historical maps as well as the Google Earth satellite images. The maps from the French colonial

archives that were not yet georeferenced (north of Kien Giang Province and Soc Trang Province) are

also stored there as Tiff files.

23

One folder contains additional historical maps found in the internet, but none as detailed as the map

series L7014. The complete file collection from the French colonial archives is stored in folder

‘FrenchColonialArchives_byOlivier’.

24

References

Albers, T., Dinh, C. S. & K. Schmitt (2013): Shoreline Management Guidelines - Coastal Protection in

the Lower Mekong Delta.

Dang, H. V. & Q. T. Le (2001): Development of Surveying and Mapping Technoligy in Vietnam. –

<http://www.fig.net/resources/proceedings/fig_proceedings/korea/full-papers/pdf/session3/dang-

le.pdf> (accessed: 20.07.2015).

GFOI – Global Forest Observations Initiative (2015): Coordination of Satellite Data Supply. –

<http://www.gfoi.org/space-data/> (29.10.2015).

Google Earth Help (2015): Use of Google Earth Imagery. –

<https://support.google.com/earth/answer/21422?hl=en> (accessed: 31.07.2015).

Google Permissions (2015): Using Google Maps and Google Earth. –

<http://www.google.com/permissions/geoguidelines.html> (accessed: 31.07.2015).

HNEE – Hochschule für nachhaltige Entwicklung Eberswalde (2013a): Geodatabase ‘Historical

shoreline mapping of the southern Mekong Delta in Viet Nam’. –

<...\Coastal_Area_GIS_database\provinces\SocTrang\CZMST_GIZ_HNEE_2013\Shoreline_SocTrang>.

HNEE – Hochschule für nachhaltige Entwicklung Eberswalde (2013b): Report ‘Historical shoreline

mapping of the southern Mekong Delta in Viet Nam’. –

<...\Coastal_Area_GIS_database\provinces\SocTrang\CZMST_GIZ_HNEE_2013\GIZ_Geodatabase_Tr

aining_2013\report\REPORTCoastLineRegion_EN.pdf>.

Madore, B. (2014): Shoreline Change from a Storm Event Procedure using the Digital Shoreline

Analysis System. – <http://sandy.ccom.unh.edu/publications/library/Shoreline_change_procedural_

2014_11_18.pdf> (28.09.2015).

Schmitt, K. & T. Albers (2014): Area Coastal Protection and the Use of Bamboo Breakwaters in the

Mekong Delta. – In: Nguyen, D. T.; Takagi, H. & M. Esteban [eds.] (2014): Coastal Disasters and Climate

Change in Vietnam. Engineering and Planning Perspectives. 107-132. Amsterdam, Boston, Heidelberg.

StackExchange.com (2014): Answers to “Does a Google Earth Pro licence allow you to export geo-

referenced satellite images for use in other GIS software?”. –

<http://gis.stackexchange.com/questions/82632/does-a-google-earth-pro-licence-allow-you-to-

export-geo-referenced-satellite-ima> (accessed: 31.07.2015).

Thi, V. T., Xuan, A. T. T., Nguyen, H. P., Dahdouh-Guebas, F. & N. Koedam (2014): Application of remote

sensing and GIS for detection of long-term mangrove shoreline changes in Mui Ca Mau, Vietnam. –

Biogeosciences 11:3781-3795.

University of Texas Libraries (2015a): U.S. Army Map Service, Series L7014, Vietnam Topographic Maps

1/50 000. – <http://www.lib.utexas.edu/maps/topo/vietnam/> (accessed: 27.07.2015).

25

University of Texas Libraries (2015b): U.S. National Imagery and Mapping Agency, Series L7015,

Cambodia Topographic Maps 1/50 000. – <http://www.lib.utexas.edu/maps/topo/cambodia/>

(accessed: 17.09.2015).

U.S. Geological Survey (2015a): DSAS - Digital Shoreline Analysis System. Computer Software for

Calculating Shoreline Change. – <http://woodshole.er.usgs.gov/project-pages/DSAS/> (accessed:

26.07.2015).

U.S. Geological Survey (2015b): The Digital Shoreline Analysis System (DSAS) version 4.0 — an ArcGIS

Extension for Calculating Shoreline Change. – <http://woodshole.er.usgs.gov/project-

pages/DSAS/version4/index.html> (26.07.2015).

U.S. Geological Survey (2015c): EarthExplorer. – <http://earthexplorer.usgs.gov/> (29.10.2015).

26

Appendices

Appendix I – Historical maps collection - 1904

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Appendix II – Historical maps collection - 1924

28

Appendix III – Historical maps collection - 1953

29

Appendix VI – Historical maps collection - map series L7014

30

Appendix V – Google Earth Satellite Images - recent images (2014 & 2015)

31

Appendix VI – Google Earth Satellite images - recent images (folders)

Appendix VII – Google Earth Satellite Images - time series (folders)