FLOOD HAZARD MAPPING TRAINNING COURSECONCLUDING REPORT"Action Plan toward Effective
Flood Hazard Mapping inVietnam"
By
NGUYEN HIEP

Department of Dyke Flood and Storm Control
Ministry of Agriculture and Rural Development
VIETNAM

CONCLUDING REPORT"Action Plan toward Effective Flood Hazard Mapping in Vietnam"
INTRODUCTION ABOUT DISASTER AND FLOOD STATUS IN VIETNAM
Vietnam is stretch of land strengthening along Indochinese peninsula which is located inSouth-east Asia. Vietnam’s mainland stretches from 23023’ to 08002’ north latitude andwidens from 102008’ to 109028’ east longitude. Length counted in straight line from
north to south stays at about 1,650km, width from west to east maximizes at 600km andminimize at 50km. Entire territory of Vietnam includes 329.241 km2 of mainland and 1
million square kilometers of territorial sea. Currently, Vietnam enjoys 64 provinces,
central cities with 622 administrative units of district and district and 10,511
administrative units of communes and wards.
Vietnam covers relatively complicated terrain: countless mountains, numerous rivers,
stretching and meandering coastline,
percentage relation between mountain andplains in mainland area indifferent amongregions.
Northern part’s topography is likeEn’eventail. Three sides of the west, eastand north are mountains and hills, south
side is coastline and the middle is plain,mainly as the Red and Thai Binh River
being
consolidated
for million years.
Central part is sloping and narrow, its
plains are closing to its coastline. The part
divided by rivers originating from western
ranges flowing into the South China Sea.
coastline are small plains. Between
mountainsides are narrow and deepmountains,cut andmountain
Alongtheslopingvalleys.

Southern part’s topography is even andLong delta is a low-lying region withheight of about 5m above the sea surface.

flat,

Vietnam territory covers 14 basin include
and large rivers with total flow of about
m3 per year. They often flow swiftly
erode the terrain, carry a large amount ofand estimated about 300 million ton per

2,860 small
867
billion
therefore
mudaway,year.

The Red and Mekong rivers are two major
important of all. The Red River originates

and the mostfrom ChineseisCuuaverageprovince of Yun Nam with length 1,140km with catchments area of 61.627 km2,including 500 km passing Vietnam with catchments area of 21.787 km2. Total flow of theRed River stay at about 150 billion m3 per year, its water is always turbid red since
carrying about 80 million m3 of alluvial per year, there fore it is called “The Red River”
Mekong River is one of 10 largest rivers in the world originating form Tay Tang (China)
with length of 1,140 km flowing through Myanmar, Laos, Thailand and Cambodia andinto Vietnam. Mekong River covers length of 4,222km with catchments area of 1 million
km2 including 220 km passing Vietnam and 4,900km2 of catchments area. Its total
flowing quantity stays at 500 billion m3 and carries away about 1 billion of alluvial peryear.
Vietnam lies in tropical region, which is
meeting place of many atmosphere blocks
resulting from continent and Equator Ocean
therefore tropical climate of Vietnam deeply
suffers from Asia monsoon regime, mainly asnortheast and southeast monsoon. However
northeast monsoon is only strong in northernand north central parts so Vietnam enjoys two
different climate regions. The north enjoys two
typical seasons: hot season is from May toOctober and cold season is from November tocoming April. The South is mainly affected bysoutheast monsoon with heat and wetness roundyear. Both parts of the country all enjoy
different climate sub-region depending on its
features of geography and topography position.
There is about 100 rainy days with total amountof rainfall of 1500 – 2000 mm per year inVietnam.
Natural disaster occurs almost round year in Vietnam, there are typical disasters in eachseason and particular characters in each region. Vietnam suffers from many kinds ofdisasters, such as: flood, storm, tropical depression, storm surge, inundation, whirlwind,
flash flood, river bank and coastline erosion, hail rain, drought, landslide, forest fire,...
The country is divided into 8 hazard.

Flooding in small rivers rises and falls
quickly, from 1-5 m3/s/km2 to over 20
m3/s/km2. Flashfloods in mid-size and small
rivers often occurs in some mountainous
provinces in the central region. High andextreme floods resulted in a high loss of lifeand extensive property damage byinundation in downstream lowlands in theRed River in 1945 and 1971, in the central
littorals in 1964 and 1999, in the Dong Nai
River in 1952, and in the Cuu Long Riverdelta in 1961, 1966, 1978, 1994, 1996, 2000,2001, 2002.

The flood in August 1945 in the Red river:
The monitoring maximum discharge
in Son Tay station in Red river is33.500 m3/s (Aug 20, 1945). Whenwater level in Hanoi reached 11.45m, the dike broke and when it
reached 12.68m, 52 parts of themain and branch river's dikes broke
which flooded 11 provinces, except
hilly and mountainous provinces.
The total flooded area was 312,000ha and more than 2 million people
were influenced by this flood. The infact loss was not fully estimated. As
the report in 1946, it was estimated that the loss was 2 billion Indochina dongs(equivalent to 4.3 million tons of rice or 2.2 billion USD). If the dikes had not broken, thewater level in Hanoi could have reached 14.1m.
The flood in August 1971 in the Red river:This was the most serious flood in thiscentury. The monitoring maximum
discharge in Son Tay station in Red riveris 37.800 m3/s (Aug 21, 1971) and total
volume water is 19,6 billion m3. Water
level in Hanoi reached 14.13 m and if thedikes had not broken and the flood had
not been distributed, water level would
have reached 14.8 m. This flood caused
devolution of 648 parts of dike of 74 km
length, overflowed and nearly overflowedother 307 parts. The total flooded area was 250,139 ha; 2,71 million people was affected.
Loss was estimated at about 7 million tons of rice or 1 billion USD.
The flood in Mekong river in 1978:
For instance, the 120 day flood in1978 in Kratie reached a total
discharge of 424 billion of cubic
meters, the daily average
discharge in 120 days was41,000m3/s.
Annually, water-related disasters
caused serious damages on bothhuman and properties. According
to the official statistics, in 2000,
total damages was estimatedabout 350 millions USD,
equivalent to 1.13% of total GDPof the country; while in 2004,
total damages was estimatedabout 250 millions USD,
equivalent to 0.56% of total GDP of the country.

THE PRESENT COUNTERMEASURES
Strategic for countermeasures in 3 region of Vietnam.
Strategy of disaster mitigation for the regions of Red river Delta and the North Midland is
to execute structural measures associated with nonstructural solutions, and measures ofstrengthening dyke systems, of diverging flood courses and of improving safety standardsof disaster mitigation works.
Strategy of disaster mitigation for Central Viet Nam is to promote flood and storm
prevention measures with the policy: ”pro-active prevention, mitigation and adaptation”.
Management and mitigation measures include construction of upstream reservoirs, ofdyke systems. These works should be combined with irrigation systems for stabilizing
agricultural production.

Strategy of disaster mitigation for the Mekong River Delta is “living with flood and floodcontrol” with specific solutions such as planning of residential clusters, construction ofirrigation systems for supplying clean water and preventing salt invasion, construction of
low embankment system for preventing salt invasion.
Organization framework:
The organization framework in
Vietnam is a system from
National to commune. The topof organization framework isGovernment.
Under
Government is two committee:
Central committee for Floodand Storm control and National
committee for search and rescue.
Also each Ministry have own
commitee.
Figure 10 and 11 presents therelationship between the central
and the local authority (province, district and commune), reporting line and decision
making power. The system is chaired by the head of the Government, the Prime Minister.
However, the management and technical power is held by a chairman (equivalent to aminister) of the CCFSC, while the search and rescue activity is held by the CCFSR.
Currently, the Minister of MARD is the chairman of the CCFSC. In reality, the CCFSC
operates based on an ad hoc basis and active in case of a flood or storm. The daily
management responsibility is held by the director of the Standing Office of the CCFSC
who is also the director of the Department of Dyke Management, Flood and Storm
Control (DDMFSC) under MARD.
From the provincial level down to thecommune level, the People’s Committee(PC) is fully in charge of the flood andstorm control plus search and rescue
activity. At provincial level, the CFSC ischaired by the chairman of the provincial
People’s Committee (PC) while themanagement and technical responsibility isheld by the director of the provincial
CFSC who is also the director of theprovincial sub-department of dykemanagement and flood and storm control. At district level, the CFSC is also chaired by
the chairman of the district PC while the management and technical responsibility is heldby the director of the district sub-department of agriculture and rural development. At
commune level, the CFSC is also chaired by the chairman of the commune PC, with one
assigned staff in charge of flood and storm control plus search and rescue activity. At alllevels, in the CFSC there are representatives from all concerned sectors and organizations,
including Red Cross Chapter.
Policies:-Land policy and land use management with the Land Law.
Policies for forest planting, protecting and forest management and exploitation
with the Law on forest protection.
Policy on managing natural resources and exploitation management
Water resources management policy with the Water Resource Law.
Policy on environmental protection, sustainable development, andenvironmental management.
Policies for flood diversion and retention and dredging riverbed for floodrelease.
Policy for disaster aftermath overcoming in disaster-prone areas.
Policies for living-with-flood areas.

Hydro and Meteorology forecast:Hydro-meteorological forecast is presently taken by the National Centre for
Hydro-meteorological forecast, Ministry of Natural resource and Environment. Its
information system is currently including domestic and international network that has
been enhanced and applied new achievements from informatics and telecommunication
technology.
There is a hydro-meteorological observation network including: 162 surface
meteorological stations, 232 hydrological stations, 788 rain gauging station and otherstation.
Specific measures of National Strategy and Action Plan for disaster mitigation andmanagement in Vietnam
Water-related mitigation measures for the Red River Delta:- Strengthening of dyke systems- Dredging of river channels for quick flood drainage- Construction flood cutting reservoirs in upstream of big rivers.
- Diversion and slowing down of flood speed.
- A forestation and protection of watershed forests.
- Improvement of dyke management and rescue.
Water-related mitigation measures for Central Region of Vietnam- Reinforce the river dyke systems and the salt water resistant embankment
systems to protect agricultural production and prevent early floods and floodtide,- Train river banks and sea borders; prevent erosion, protect densely populatedareas and important manufacture zones; gradually stabilize big river mouths;
facilitate flood discharge, etc.
- Build and improve the canal systems and upstream reservoirs,

-Search and rescue works have been implemented efficiently when an affectedarea is in a severe disaster.
Rearrange crop patterns and animal-breeding patterns to suit topographicaland production conditions in disaster-prone areas in order to avoid floods inthe main cropping season.
Forest plantation in upstream watersheds and along coastal areas,
New residential areas are being planned and built away from flashfloodprone, inundation-prone, storm surge-prone and erosion-prone areas.
Shelters for fishing ships and local fishermen are built along the coastline ofCentral.

Water-related mitigation measures for the Mekong River Delta of Vietnam
Guidelines, solutions, and plans for flood control and disaster mitigation in the Mekong
Delta of Vietnam are the following:- Sustainable development in this flood-prone environment, and coexistence
and accommodation to flooding.
- Programs that prevent salt water intrusion resulting from tides and storm
surges are given priority, to better consolidate conditions for sustainable
development in the Mekong River Delta.
- Flooding is an important issue in general, and flood control in the MekongRiver Delta is even a more difficult and complicated task,- Similarly cooperation with the upstream riparian countries in the MekongRiver Basin must be followed to be able to mitigate and to manage floods inthe Mekong Delta region of Vietnam.
FLOOD HAZARD MAPPING IN VIETNAM
Flood is a main disaster in Vietnam. Every year flood occurs in 3 regions (North, Middleand South). Flood hazard map is a very important tool. It is a non-structure measure forflood damage mitigation. In the future, Flood hazard map will be developed in all flood
plain area.
The North of VN has the complex dike system, but the dike breaking risk is very
realizable on the big flood. In addition, there is a division area in the design flood. Theflood hazard map will be built with scenario dike breaking and design flood.
In the middle of VN, there isn't complex dike system. Besides, dike system only protects
land in the early flood season for field. In the main flood season, water overtops the dike.
Flood makes inundation area. The flood hazard map will be built with scenario of everyflood year .
In the part of mekong river in Vietnam, flood from river comes to flood plain every year.
Every year, there are flood plains in some areas in 4 - 5 months. Flood Hazard map is atool for evacuation and establishment of land use plan.

With the country which is very influenced by food like Vietnam, making Flood hazard
mapping will be developed in near future. The map will help save life and properties ofpeople in flood plain and contribute to suitable development proccess.
THE MAIN ORGANIZATION RESPONSIBILITY FOR MAKING ANTICIPATED
INUNDATION AREA MAP:
Standing office of Central committee
for Flood and storm control that is
also is Department of Dyke
management flood and Storm control
is main organization responsibility
for making anticipated inundation
area map. The organization will
combine with related organization,
local government and people in theflood area to making the map.

THE MAIN ORGANIZATION RESPONSIBILITY FOR
DISSEMINATING ANTICIPATED INUNDATION AREA MAP:

MAKINGAND

Local government in province,
district and commune that isprovincial,
district,communecommittee for flood and stormcontrol
will
bethemainorganization
responsibility
fordisseminating anticipated inundationmap.

THE "ACTION PLAN" OF MAKING FLOOD HAZARD MAPS IN YOUR COUNTRY.
Target river basin area is Thach Han river basin, in Quang Tri province.
Thach Han river originated from Truong Son mountain is 150km long. Main river called
Dakrong flows from upstream throuth Da Ban mountain to Ba Long, changes direction toNorth-east and come to sea in Cua Viet river mouth. The area basin is 2500 km2.
Thach Han river has 3 main branches such as: Rao Quan (251 km2), Vinh Phuoc (293km2), Cam Lo (539 km2). The basin average altitude is 301m, average slope is 20%,
average width is 38.6km, river density is 0.92m.

From survey and monitoring, there are some big floods occuring in Thach Han river suchas in oct 1923, oct 1983, oct 1985, oct 1990, oct 1992 and oct 1999. The biggest flood
occur in oct 1989. Rainfall in one day is 609 mm. Maximum of water lever in Thach Han
station is 7.11m (31 October 1983). Maximum discharge in Thach Han is 7590 m3/s.
Necessity to make flood hazard map in Thach Han, Quang Tri.
- There are many floods in the river.
- Quang Tri city which is a famous and tourism place in Vietnam locates in thedownstream. The city is developing.
- The Thach Han basin has simple river system, there isn't so many diversion
river, easy to apply HEC RAS for making flood hazard map.
The effect of flood hazard map in Thach Han river.
- The FHM is a tool to plan residential area, land use.
- The FHM is basic data to make evacuation planning.
- The FHM help people in flood plain area to improve capacity, decrease
vulnerability and give more information for evacuation.
- The FHM will decrease damage in life and property.
The data and related problem to make flood hazard map in Thach Han river.
- Rain fall data
- Discharge data
- Topographic data
- Administration map- Land use.
- Irrigation and drainage system, reservoirs.
- Transportation system.
- Inundation area in 1983 and 1999.
Action plan on making and disseminating FHMContent
Reviewing the existing inundation
map in Thach Han, Quang Binh
Collecting data related to making
FHM in Thach Han, Quang Binh.
Implementing FHM to Thach Han,
Quang Binh with participation oflocal government and people in theflood plain region.
Getting more comments about theFHM, completing and disseminating
FHM.
Applying to other region in Vietnam.

2007

2008

2009

2010

2011

Problems in making FHM in Vietnam.
- FHM is a new field with people and local government in Vietnam.
- Rainfall, discharge data are not enough to make FHM (Almost rainfall data
are 6 hour data, some rainfall stations can monitor hour data.)- Inundation area data are not exact, so it is very difficult to verify between
simulation and in fact.
- Quang Binh is a coastal province, effected by tide so that the simulation forthis area is more difficult- The limit budget for non-structure measure for damage mitigation of disaster.
- Awareness of people in this area is limited.
The solution for the problem mentioned above.
- Choosing small pilot location with small complicate river system .
- The location is usually inundated in many years and a famous place inVietnam.
- Use the existing data in Office and from other project.
- Combining with other organizations, local government and people in the flood
plain area.
The improvement from FHM on Ise city currently.
- We try to add more information about evacuation route. Adding more
temporary centres in the inundation area. But we have not checked the place
which can be the temporary centre yet.
- Make FHM in English version
CONCLUSION- Flood hazard map is a very important tool for mitigating flood damage.
- Flood hazard map is useful for evacuation work, land use planning andimproving awareness of flood situation for people in the flood plain.