MINISTRY OF EDUCATION

VIETNAM ACADEMY OF

AND TRAINING

SCIENCE AND
TECHNOLOGY

GRADUATE UNIVERSITY OF SCIENCE AND
TECHNOLOGY

-----------------------------

NGUYỄN CÔNG QUÂN

GEOMORPHOLOGY OF COASTAL ESTUARIES IN
NORTHERN CENTRAL VIETNAM

Major: Geomorphology and Paleogeomorphology
Codename: 09 44 02 18

DOCTORAL DISSERTATION SUMMARY

Hanoi 2019


The doctoral dissertation was accomplished at the Graduate
University of Science and Technology – Vietnam Academy of
Science and Technology.


numerous external, internal and artificial dynamical processes;
furthermore, these are also stage for complex river-ocean
interactions. The consequence of those processes has made coastal
estuaries prograde toward the sea since Pleistocene epoch to the
modern day, formed identical type of landform from shoals,
sandbars, sand barriers to deltas. Coastal estuaries are normally
favourable places for socio-economic developments, but they are
also intimidated as sea level risings which can cause coastal erosion,
flooding… and damage coastal construction and lives of local
residents.
In the context of global climate changes and sea level rise, and
under the pressure of the economy, growing socio-economic
development, the topology of coastal estuaries on the Northern
Central Vietnam has been drastically transformed at many time and
spatial scales. This dissertation titled “Geomorphology of coastal
estuaries in northern central Vietnam” is the final result of studies to
fulfill the necessarirarity of many urgent objectives toward
sustainable socio-economic development and environment
protection.
2. Objectives
- Interpret the geomorphological features of coastal estuaries in
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northern central Vietnam.
- Estimate the course of morphological changes and
geomorphological dynamic processes in the study area.
3. Research subjects and Study
- Research subjects: Morphology and modern geomorphological
dynamic processes of coastal estuaries in northern central Vietnam.

Holocene – Upper Holocene, and Upper Holocene – present, and
propagraded at different grades. The present development at each
estuary is ranging from progradation (Ma estuary) to severe coastal
erosion and retrogradation (Thach Han and Huong estuaries).
6. New findings in the dissertation
The detailed geomorphological maps of the three coastal estuaries
had been established using high resolution remote sensing images,
GIS technology and other traditional research methods, to classify
and interpret landforms into groups of similar morphogenesis and
age. The geomorphological maps were adapted to understand the
morphological changes in the studied areas from late Upper
Pleistocene to Holocene.
The late Upper Pleistocene shorelines of the Thanh Han and
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Huong coastal estuaries, and the late Middle Holocene shoreline of
the Ma coastal estuary had been reconstructed using
geomorphological and geological evidences. Database compiled
from topological maps, remote sensing data and GIS was used for
reconstruction of temporal shorelines in Thach Han and Huong
estuaries for the period from 1952-2017, and shorelines in Ma
estuary from 1965-2017.
Modern morphology change patterns of the three estuaries had
been determined. Dominant process in Ma estuary is progradation to
form new seaward landform, meanwhile coastal erosion is dominant
in Thach Han and Huong estuaries and causes retrogradation.
7. Scientific and practical significances:
Scientific significance: Results of the dissertation provide sufficient
database on the morphological changes, estimate the orientation of

synthetic geology-geomorphology criteria:
- Convex type (delta) on Hoi river mouth where characterized by
front submerged bars.
- Straight type (liman) on Viet and Thuan An river mouths,
characterized by low sediment concentration and parallel sand
barriers and enclosed lagoons.
1.2. Literature review
1.2.1. Global research
Globally, the methodology for coastal estuary study becomes
more synthetic and completed with the adaption of modern
technologies toward quantification outcomes.
1.2.2. Vietnam
Most studies on this field in Vietnam implemented modern
morpho-dynamic processes evaluation and their correlation to typical
natural hazards of coastal estuaries in northern central Vietnam on
determine the cause, estimate potential risk and propose mitigation/
damage reduction measures.
1.2.3. Northern central Vietnam
Study on the morpho-dynamic issues of coastal estuaries for
planning and territorial organization for socio-economic
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development in the northern central Vietnam is scarce, thus it is
necessary to perform more concrete and detail research on each
estuary.
1.2 Methodology
1.3.1. Approach
1.3.2. Methodology
1.3.2.1. Field survey and measurement technique

Severe erosion has occurred on river banks and coastal sections
where are active faults intersections.
2.3 Morpho-dynamic systems
2.3.1 Holocene sea-level fluctuations
Sea-level fluctuations on the northern central Vietnam in
Holocene were similar to the general trend in Vietnam and adjacent
regions.
2.3.2 Climate regime
Study area lies in the monsoon tropical climate, with two
separated dry and rainy seasons, under significant influence of
marine atmosphere.
2.3.3 River flow and sediment patterns
Water and sediment discharge of Ma river are considerably
greater than those of Thach Han and Huong rivers, thus the role of
Ma river to the formations of its estuary on the initiation and modern
morphology changes is more dominant than the other two rivers.
2.3.4 Wave, tidal and nearshore current regimes
Wave influence to the coastal estuaries in the study area is
dominant in the winter, thus the coast is severe shaped and erosion.
Tidal regime in the estuary of Ma river is greater than the other
estuaries, thus increase its influence to the estuarine formations.
Smaller tidal amplitude in Thach Han and Huong estuaries play less
significant role in morphological changes of those areas.
2.3.5 Modern sea level rise and climate changes
Sea level rise is a significant factor that has direct influence to the
morphological change of coastal estuaries in northern central
Vietnam.
2.4 Anthropogenic elements
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were classified into group. Each morphological group was
established according to its age and morphology.
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3.2.2 Geomorphology of Ma estuary
- Karst formations: karst formations in the study area distribute as
isolated mounts with height over 30m, scattered to the north and
southwest of the Thanh Hoa city and northwest of Ham Rong
mountain.
- Abrasion formations: those formations distribute scattered in the
study area, as isolated mounts and hills over 20m on different kinds
of bed rock.
- Alluvial formations: deposition formations by alluvial processes
distribute along the main channel of Ma river. They are classified
into 3 units: Upper Holocene shoals (1-2m); Upper Holocene low
sandbars (1-2m); and Upper Holocene high sandbars (1-2m).

Figure 3.1. Geomorphological map of Ma estuary
- Marine formations: this group includes 3 morphological units:
Upper Holocene accumulation terraces widely distribute in Hoang
Hoa, Quang Xuong districts and Sam Son city, height of 2-3m;
Lower-Middle Holocene accumulation terraces distribute to the west
of Hoang Hoa, Dong Son, Thieu Hoa districts and Thanh Hoa city,
height of 3-4m; modern beaches lie along the coast of Hau Loc,
Hoang Hoa, Quang Xuong districts and Sam Son city.
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- Heterogeneous formations: this group contains 7 formations of

over 20m; Upper Holocene abandoned river channels. Alluvial
formations concentrates mainly on the riparian of Cam Lo (Hieu) and
Thach Han rivers.

Figure 3.10: Geomorphological map of Thach Han estuary.
- Marine formations: this group includes modern beaches along the
coastline; Lower-Middle Holocene accumulation surfaces distribute
across Gio Quang, Gio Viet, Ha Tay and Ai Tu county; Upper
Pleistocene and Middle-Upper Pleistocene abrasion terraces, at the
height of 12-20m and 25-35m respectively, to the west of the study
area and on the margin of the deposition plain.
- Heterogeneous formations: this group contain formations which
developed by alluvial, marine, bog and aeolian processes. The most
widespread formation is Lower-Middle Holocene alluvial-marine
accumulation surfaces at the height of 2-6m which accounting major
area of Thach Han estuary. Middle-Upper Holocene and Upper
Holocene deposition plains narrowly elongate across Gio Mai,
Tuong Van, Cao Ly at the height of 2-4m and 1-2m, respectively.
Upper Pleistocene alluvial-marine accumulation surfaces spread as
small patches in western Gio Quang, Dai Ang at the height of 6-15m.
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Upper Holocene and Middle-Upper marine-bog accumulation
surfaces distribute at the height of 1-2m and 1-3m, respectively and
scattered as small patches, flooded year-round. Elongated marineaeolian coastal sand dunes spread along the modern coastline.
3.2.3 Geomorphology of Huong estuary
- Abrasion formations: compiled denudation formations distribute at
the height over 20m in Huong Ho, to the south of Kim Ngoc village,
Gia Kho, Nguyet Bieu, Duong Xu, An Ha.

RATIONAL USE OF TERRITORIAL RESOURCES OF
COASTAL ESTUARIES IN NORTHERN CENTRAL
VIETNAM
4.1 Morphological evolution of coastal estuaries in northern
central Vietnam
4.1.1 Middle – Late Pleistocene era
In Middle-Late Pleistocene era, the tectonic activities became
diverged as subsidence to the east, uplifting to the west of coastal
estuaries in northern central Vietnam. Marine transgressive boundary
shifted inland which was favourable for sedimentation in the east,
while abrasion terraces initiated and developed to the west of study
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area.
In the estuary of Ma river, the 15-35m abrasion terraces initiated
in Tho Xuan and Trieu Son districts (Thanh Hoa province).
Denudation and denudation-erosion on mounts and hills over 40m
height took place in Yen Dinh, Tho Xuan and Trieu Son districts.
Subsidence occurred beneath and to the east Ma estuary in coherence
with marine transgression were the dominant environment for the
formations of marine and alluvial-marine landforms.
On the coastal estuaries of Thach Han and Huong river, abrasion
terraces also distributed to the west of study area, at the height of 1535m. Prodominant morphodynamic processes including denudation,
denudation-erosion and abrasion occurred in the background of
uplifting to the west of study areas, and stepping subsidence and
deposition on the major of Thach han and Huong estuaries. Uplift
activities promoted surficial denudation, erosion and eluviation to
form slope denudation, denudation-eluviation, denudation-deposition
surfaces, abrasion marine terraces. Mountains developed on uplifting

Huong Long, Huong An, Huong Thuy and northern area of Phu Bai
Airport. The surficial height was 5-10m in average, in some places it
could reach up to 20m such as Nam Giao Esplanade where was
relatively levered, composed from gravely sand mixed up with
yellowy red clayey silt, tampered, occasionally laterization. The
alluvial-marine-lagoonal deposition plains widespreaded and
accounted for the majority of Hue coastal plain in Phu Vang and
Huong Thuy districts.
4.1.3 Late Holocent to present
In Ma estuary, local subsidence in Ma rivermouth was filled by
thick layer of late Holocene sediment, which reached up to 30m as in
drillcore LK11.SS in Lach Trao river mouth. Other morphodynamic
processes were alluvial, alluvial-marine, marine-bog… Deposition
landforms distributed along the river channels, coastal zone and river
mouths. The sedimentation determined the modern formation of sand
bars, sand barriers, sand ridges and dune systems in Ma estuary. In
Len river mouth, tidal flats, sand bars and shoals enlarged
continuously and gradually due to abundant sediment supply.
Shoreline advance rate in this area reached up to 40-50m per year.
Sediment supply in Hoi river mouth was smaller, thus the
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sedimentation was also weaker, accumulation occurred to both north
and south sides of the river mouth, shoreline advance rate was 5-10m
annually.
In Thach Han and Huong estuaries, tectonic activity was diverged
with prominently subsidence to form floodplains, marshes and
lagoons as narrow strips along the coastline from Duong Thuong to
Ke Sung. Beside, alluvial formations also emerged on the riparian of

North of Hoi rivermouth
South of Hoi rivermouth
Rate of change
Rate of change
Period
Status
(m/y)
(m/y)
Status
Conclusion
Conclusion
Maximum Average
Maximum Average
1965Slightly
slightly
(-)
10.8
3.1
(+)
12.1
4
1975
retreat
advance
1975Moderate
Slightly
(-)
18.7
4.2
(-)

seaward at relatively high rate. During late Pleistocene to middle
Holocene, the estuary advanced seaward up to few tens’ kilometers.
From late Holocene, the estuary gained more than 20km seaward.
Evaluation of modern morphological changes of Hoi and Lach
Truong rivermouths were energetic, thus showing the movement
trend of the shoreline in near future (Figure 4.5).
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4.2.2 Morphological changes of Thach Han estuary
The estuary of Thach Han river was initiated since late
Pleistocene according to research results on local geomorphology
and geological settings. In late Pleistocene, the mainland lied distant
from modern shoreline, while local subsidence promoted marine
transgression deep into the mainland and the majority of Thach Han
estuary submerged. In late Holocene, uplifting activities and marine
regression took place and formed coastal plains. From 1952 to
present, the estuary has changed diversely as shown in Table 4.4.
Table 4.4.. Coast status of Thach Han estuary
Period

Cua Viet coastal zone
Interior of Cua
Northern
Southern
Viet
coast
coast
rivermouth


Shoreline retreat/advance
alternatively, tend to be stable
(-)
(+/-)
southward. Minor change in
rivermouth.
Prodominent shoreline retreat on
northern coast, alternative
retreat/advance on southern
(+)
(+/-)
coast, relatively stable. Change
reduced southward. Prodominent
erosion inside channel. Minor
change in rivermouth
Prodominent shoreline retreat,
slight alternative retreat/advance
(-)
(+/-)
inside channel. Significant
change in rivermouth.
Advanced shoreline, significant
(+)
(+/-)
change inside channel. Unstable
rivermouth.
Moderage shoreline advance,
alternative shoreline
(+)
(+/-)


Figure 4.9. Morphological changes of Thach Han estuary (Cua Viet
rivermouth)
4.2.3 Morphological changes of Huong estuary
Morphological changes in Huong estuary took place from late
Pleistocene to present at a vigorous pace. In late Pleistocene,
mainland of Thua Thien-Hue lied remotely inland from modern
coast, as in Huong Tra, Huong Thuy, Phu Loc districts and west of
Hue city. Uplifting movement and marine regression since late
Holocene had resulted a modern coastal strandplain. In the modern
period from 1965 to present, Huong estuary has experienced some
diverse transformation as shown in Table 4.6.
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Table 4.6. Coast status of Thuan An estuary
Period

North of
Thuan An
rivermouth

1965-1978

(-)

1978-1989
1989-1994
1994-1999
11/1999

(+/-)
Less stable coast
(-/+)
(+/-)
Less stable coast
(+/-)
(-/+)
Less stable coast
(-)
(-)
Rapid erosion
Relatively stable
(+/-)
(+/-)
coast
(-/+)
(+/-)
Less stable coast
Thuan An
rivermouth was less
Morphological stable, undergone
changes due to
influence from
economic
alluvial-marine
Less stable
movements,
morphodynamic
less stable
factors, mineral

Research results on the morphological changes of river channels
could be used as basic scientific platform to propose planning
direction and measuarement toward effiency use of waterways.
4.3.4 Marine tourism
Decision makers can propose ideal concrete plan or projection
toward natural hazard mitigation via using study results on
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geomorphology and morphological changes of those coastal
estuaries, thus promote sustainable marine economic development of
the northern central Vietnam.
CONCLUSIONS
The morphology of coastal estuaries in northern central Vietnam
initiated and developed in the extreme and diverse settings of
internal-external morphodynamic factors and anthropogenic
processes. Neotectonic and modern tectonic movements with the
tectonic fault systems played a crucial role, which controlled and
dominated the development and transformation of estuaries’
morphology in the study areas.
Geomorphological maps scaled at 1:50.000 of the coastal
estuaries of Ma, Thach Han and Huong rivers had been established
using homogeneous landform classification by fusion methodology
of conventional geomorphological methods, high resolution remote
sensing techniques and GIS techlonogies.
The coastal estuaries of Ma, Thach Han and Huong rivers were
classified as delta and liman types and developed since middle-late
Pleistocene to present. The delta of Ma estuaries consisted of 3
alluvial landforms, 3 marine landforms and 7 heterogenous
landforms. The liman type of Thach Han estuary developed 4 marine

advantageous for economic development in tourism, transportation,
aquaculture and deposit placer exploitation. As the consequence, it is
necessary to establish a master plan for reasonable use of territorial
resources based on the outcomes of modern morphological change
study, toward sustainable socio-economic development and
environmental protection of the northern central Vietnam.

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