Influence factors to flood disaster and search and rescue capacity in Thua Thien Hue delta

Thua Thien Hue delta is one o f the strongest areas affected b y natural disasters, esp ecially disasters related to water disasters such as floods, landslides coast.. T o have a scient

VNU Journal o f Science, E arth Sciences 28 (2012) 153-159

Influence factors to flood disaster and search and rescue

capacity in Thua Thien Hue delta

Pham Thanh A n ’’*, Dao Dinh Bac^, N hu Thi Xuan^

^Search a n d R e sc u e T ech n ica l S e n i c e C en ter,

S u rv e y a n d A e r ia l M a p p in g C o rp o ra tio n -D e fe n c e M a p p in g A g e n c y

2 /1 9 8 Tran Cung, T u L iem , H an oi, V ietnam

^ G eo g ra p h y Faculty^ V N Ư U n iv e rsity o f S cien ce, 3 3 4 N g u y e n Trai, H a n o i, V ietnam

R eceived 05 July 2012; received m revised form 6 Auiiust 2 0 1 2

A b stra ct Thua Thien Hue delta is one o f the strongest areas affected b y natural disasters,

esp ecially disasters related to water disasters such as floods, landslides coast T o have a scientific

basis for the proposed m easures to prevent and respond to m itigate the dam age and assist in

search& rescue in the event o f floods need to study the factors that affect stroke flood s and search& rescue capacity.

T his paper has identified the natural and man-made factors affecting flood disasters and search& rescue activities w hen disasters occur flood on Thua Thien Hue delta In particular, major role as geographical location, the study area is located in the transition zone b etw een the Northern clim ate and Southern clim ate, the place where the dispute betw een the different air pressure, with

m orphological characteristics o f terrain, exừ em e weather, resulting in Thua Thien Hue delta is

often effected by various types o f natural disasters related to water disasters, esp ecia lly floods.

The result analysis o f the factors causing floods w ill be the scien tific b asis for early warning,

prevention and response, efficien t support for search& rescue activities to reduce the lo ss o f life and property when flood disasters occur in Thua Thien Hue delta.

1 Context

Flooding is a natural hazard phenom enon,

the result o f the concenfration o f w ater large

am ounts and overflow ing into low teưain area

m aking w ide flooding, causing dam age not only

to people and property that also a long-term

negative im pact on the environm ent such as

w ater pollution, disease

* Corresponding author Tel: 84-988528809

E-mail; thanhan74@gmail.com

Thua T hien H ue delta is one o f the strongest areas affected by natural disasters, especially disasters related to w ater disasters such as floods, landslides coast In flood history (X I/1999) w ith flood peaks exceeded the alaưning III level, T h ua Thien Hue has m ade plain im m ersed in w ater, d esừ oy ed several residential areas, killing hundreds o f people, dam ages estim ated trillion It is the direct physical dam age, and the dam age to the ecological environm ent can not fully assess

153

154 F T A n et al. / V N U Journal of Science, Earth Sciences 2 8 (2012) 153-159

To have a scientific basis for the proposed

measures to prevent and respond to m itigate the

damage and assist in search& rescue activities in

the event o f floods need to study the factors that

affect sứoke flooding and the ability to search

and rescue This is the research content o f this

paper

2 The factors that affect flood hazard and

the ability to search and rescue when

disasters occur on Thua Thien Hue delta

The cause o f the flood disaster is derived

from two basic factors, natural factors and man-

made factors These factors are affected both

directly and indirectly to the flooding Comm on

factors independent nature, but in m any cases a

com bination o f both nature and m an-m ade

N atu ral fa c to rs: o f endogenous and

exogenous origin

Endogenous factors has a very im portant

role, it indirectly affect flood on the earth's

surface Endogenous factors, tectonic activity

and new tectonic new in the process o f

formation o f the surface and hydrological

netw ork and the form ation o f the delta is a very

im portant role Endogenous process usually

takes very long geological cycles at a slower

rate but there is a very decided, create the

geological foundation o f a large basin

Exogenous factors include landscape factors

and the local landscape They have both direct

and indirect im pact to flood through the role o f

vegetation and nature o f seasonal hydrological

regim e o f rivers and oceanographic regim es

rain - flood the continent, w aves, tides, ocean

circulation, sea-level rise

Natural factors interact w ith each other in

the system consists o f tw o m ajor sub-system s to

generate flood or floo ding phenom enon in general T he first su b -sy stem reflects the state

o f atm ospheric p recip itatio n (rain, a com bination o f facto rs m onsoon with atm ospheric d istu rb an ce factors) and abnormal changes o f sea level for the coastal areas, such

as w ater level, w a te r is draw n and unusually high tides T h e secon d sub-system consists o f the factors reflectin g the p resen t state o f terrain buffer on tw o m ain aspects, w hich is the condition o f w ater to cause flooding or high flood level, o r even g en erate flash floods, flood debris T h is is d eterm in ed p rim arily by the topography typ e is clearly on the digital elevation m odel (D E M ): the presence o f the surface form sm all abso lu te height, the low range relative to around, etc, the second characteristic o f th e te ư a in buffer is the perm eability or w a te r im p ed ir is defined by the characteristics o f the vegetation , the physical properties o f the m an tle and crust o f the soil, the surface layer o f the lithosphere, the characteristics o f the p aren t rock, etc Both aspects o f the te ư a in b u ffer are reflected in the

geom orphological ch aracteristics o f the terrain

o f the area So, co u ld be attributed to the analysis o f the in teractio n o f natural factors on fertility and flood in und atio n o f the analysis consists o f three co m po nents: state o f the atm osphere - the ph y sical te ư a in characteristics

- arising terrain (g eo m o ip ho lo gical) In this interaction, i f the p ro cess o f w ater volum e win, will generate flo o d in g in varying levels, depending on the w ater v olu m e on the low terrain; co n ừ ary , w hen th e p rocess o f w ater drainage w in, ex trem e w ater levels w ill not appear B y th at logic, for T h u a T hien H ue delta,

we can see the sensitivity floo din g as follows:

- T he area is flo od ed ju s t no rm al due to the rainy season, th e m o st sensitive;

P.T A n et al. / V N U journal of Science, Earth Sciences 28 (2012) 153-159 155

- The area flooded by rain in storm

situations single season, second kind o f

sensitivity;

- The area flo od ed by rain in storm

situations seasons co m b in ed w ith tropical

convergence circulation, th ird -sensitive type;

- T he area is floo ded b y rain in hurricanes

husband situations co m b in ed w ith fropical

convergence circu latio n and N E m onsoon

circulation, the fourth categ ory sensitive;

Easy to u nderstand the depth o f flooding,

duration o f flooding an d the level o f cause

hazard also increased in the o rd er m entioned

above [1]

M a n -m a d e fa c to r s : a very im portant

decision factor to regu late the n atu ral flow from

upstream is the rap id flu ctu atio n s o f w atershed

vegetation due to deforestatio n, m ining and

econom ic purposes o btain lan d for fanning,

cattle breeding T h e rap id d eclin e o f vegetation,

especially in the cu rren t w atersh ed protection

forests have lost the ability to slow dow n the

flood, the flow o f surface w ater, and this is

actually one o f the m ain causes o f the the flood

disaster In addition, the co nstructio n o f many

w orks to regulate w ater reservo irs, dam s, dams

regulate w ater, reco u n ts line, w h eth er they

shore spillw ay, salty dam , dredging has

changed the n atu ral h y d ro lo g ical regim e o f the

river, and the traffic system , housing also

im pede drainage causing flooding O n the other

hand, planning in the d istrib u tio n o f population,

the civil, social and econ om ic decision likely

hurt their d ifferent and th erefore also the

dom inant direction o f search and rescue

activities

D ue to the to p o g rap h y and geom orphology

o f T hua T hien H ue delta h as characteristics

than even the n earb y co astal delta o f the central

coast (as the T h u B o n R iv e r D elta) and the

dialectical relationship betw een they are for

floods (flood left their m ark on the terrain, and

then record the im pact o f the flo o d through various changes it has gone through), so the

study o f the geom orphology fraces and w eather patterns causing floods will contribute to clarify the scale, causes and potential flood damage

2.1 N atural fa c to rs

G eographical location: situ a ted in the clim atic transition zone betw een N orthern and Southern clim ate that ranges Bach M a is the natural clim atic boundary betw een the two regions, and is located in the boundaries o f the typical tropical areas w ith limited the 16 degrees latitude, the place w here the dispute betw een the air flow com es from the different air pressure center: from the N orth came down, from the W est pass, from the encroaching on the East and from the South move up, usually the com bination o f extrem e w eather phenom ena, and so located downsfream o f low and m edium m ountain ridges get wind, rain

w elcom e in W estern Thua Thien Hue, a center

o f heavy rain m ost o f Vietnam; boundary betw een typical ứ opical equatorial region should usually have m any strong w eather disturbances; located in the m iddle part o f the shoreline segm ents from Thanh Hoa to the exứem e South central perpendicular to the dom inant w ind direction N orthE ast coast often blocked by the estuarine sand trip and the sand bar extends parallel to the shore These characteristics o f the geographical location is one o f the m ain causes for here regularly suffered the ravages o f stonns and flooding As

a result, there are often m any types o f natural disasters related to w ater disasters, especially floods This set for the search and rescue activities w ith specific objectives is to focus

156 P.T A n et al. / V N U Ịournal of Science, Earth Sciences 28 (2012) 153-159

energy and m aterial resources to respond

m ainly to the flood disaster in the region

Topography: if Southw est m ountains with

very steep teưain beneath the coastal delta is

both low and not slope T hat m akes conditions

for the flood took place so quickly in the study

area

A teưain quite com m on in Thua Thien Hue

delta IS in the N ortheast o f the dunes running

parallel to the coast w ith a height o f 5-30m, the

two asym m etric ribs, ribs fairly large W estern

slope 25"’-30°, the Eastern slopes laid over lO'’-

15° These dunes make this delta having low

trip after dune, estuarine is narrow , difficult to

escape the w ater and the sand pressed into the

estuary shore, forced to flow in the stream leads

not slope, parallel to the coast, so that rapid

flooding w hen there is heavy rain, w ater from

the W est down

Geology: the structure has decided to form

the topography o f the delta by the parallel

orientation o f the bar, the val-shore and

estuarine sand trip extends in N W -SE direction,

the same direction as the sand bar and m odem

shore It is also a very notable feature o f the

Thua Thien Hue delta, because they m ake a

"grabens" valley and closed [2]

Climate: the interaction betw een the

monsoon circulation and the topography o f

South Truong Son m ountain did appear a

special variable type the rain is hea\7 rain

during the autum n and w inter and less rain in

the spring-sum m er period, range pearling in the

W est form a wall o f rain took alm ost the entire

amount due to w eather disturbances caused

when w inds from the east or in the w inter

monsoon blow s from the N ortheast The

w eather is rainy situation even m ore pow erful

com bination o f interference w ith operation o f

the tropical convergence zone, and main

characteristics o f rain, storm s and tem perature, the characteristics o f the atm ospheric circulation and its interaction w ith the teưain did appear in this area disaster situations dangerous as flood floods, riv er bank erosion, coastal .[3]

H ydrographic netw ork: in general, due to

rain seasons, the rivers are short and steep,

v e g e ta tio n c o v e r w a s b a d ly d a m a g e d , so the

extrem e fluctuations in a flow ; the rainy season they are rivers full o f w ater, the w ater can repeatedly hit causing m ajo r floods bring disaster, while in the dry season, the v a lle y

floor are usually shallow , rev ealin g the vast golden sand, his m asterpiece receiv er narrow,

by rainfall concenừated on the narrow and steep, so the rivers are large flood p eak flow is usually very high B esides the ancient river system, there is no recom m ended flood, so the flood waters, they reactivate and foHTi the large flow o f flood A long w ith the rapid transition from steep m ountains to the low er thus accrue delta will very quickly, b ecau se there is flow not directly into the sea w h ich w as congestion

in the lagoon due to the floating sand dikes high flood events here can happen v ery quickly

O ceanographic regim e: sea salt contribute

to speed up the process o f the t>pical brackish coastal lagoon on the T am G iang-C au Hai, affect the structure o f ửie ex isting species, prom ote agricultural im plem ent m ore thorough and salinity solutions, esp ecially solutions

w orks and therefore also affect the ability to flood the region's natural m ig rato iy species groups R ising sea levels also change the process variable te ư a in coastal and wetland expansion on the Tam G iang -C au H ai lagoon and the coastal plain, increasing the im pact o f floods on Thua Thien H ue d elta and the Huong river Basin [3]

P.T A n et al. / V N U Journal of Science, Earth Sciences 28 (20Ì2) Ĩ53-159 157

S oil characteristics: barren hills m ainly in

the m ountainous areas w ith steep slopes, the

source o f the river, so the rainy season increases

the risk o f d isaster phenom ena such as floods,

flash floods and m ud rocks, erosion, landslides

occur very serious

Vegetation co ver a n d lakes: Forest area

accounts for a large proportion o f natural land,

but over the years the forest has been

significantly, from the ability to regulate flood

basin fell, po or w ater holding capacity,

com bined w ith slope increase flood flow

coefficient T he lag oo n area lakes in the

province accounts for nearly 5% o f the territory,

but m ainly n ear the sea so little to regulate

G eom o rp hological characteristics: with

geom orphologic characteristics w ith the

characteristics o f the central region, may have

noticed, we d eterm ine the structure o f these

four countries, the d irection o f flow, the process

o f accretion and erosio n direct reflection o f the

operation o f the flood, inundation Research

and evaluate the ro le o f geom orphology o f the

delta and Its inherent characteristics related to

floods, really very u sefu l and effective for the

proposed solutions to cope later A pplying the

achievem ents o f G IS w ill help, assist in

analysis, calcu lation o f spatial data and

associated rem ote sen sin g data, digital elevation

m odels, esp ecially w h en com bined w ith expert

know ledge analysis in geom orphology and

flood characteristics can m ake m ore accurate

judgm ents flood sensitiv e areas, the relationship

- this reflects that zo nin g areas at risk, build

scripts p revention an d search and rescue plan in

case o f flooding [2]

2.2 The m an-m ade fa c to r

It is an im po rtan t factor in prom oting or

reducing the risk o f flood disasters I f the

developm ent and im provem ent activities have calculated the risk o f com plications, the level o f risk is down, even if developm ent does not take into account the influence o f the level o f flood risk due to accidents, the result is incalculable Exploitation and im provem ent o f the natural teư ain for social life so grow ing human factor

in increasing flood caused

Due to pressure o f increasing coastal population and, o f course, is the economic developm ent needs requires more area under cultivation and housing, has led to the exploitation o f the teư itory o f a lack o f

m anagem ent, serious encroachm ent coastal flood corridor The uneven distribution o f population concentrated m ainly in the plain, on both sides o f the river downsfream Along with econom ic activities such as sightseeing tourism, industry, agriculture, aquaculture fishing have very sừong im provem ent o f virgin teưain Residential areas located along the high ridge along the river espécially Hue City including

m any unique ancient architecture is built on alluvial o f H uong river along with high walls and drainage system s naư o w , the water overflow s the banks will cause huge damage

D espite dense irrigation network, including rivers, canals dug in Huong Thuy, Phu Vang district, but by digging a long time, should not

be dredged regularly now heavily sediment, making flood drainage capacity greatly reduced

N o large-scale reservoirs, w ith a capacity o f about 55 m illion o f flood control level is not high Existing irrigation in the plain key role to provide irrigation w ater, rather than drainage Therefore, in som e places this apparent draw back system like the roads to slow the drainage flood plain w hen surface runoff

Roads often have higher than the natural terrain o f about 0.5m to 2m and m ain traffic

158 P.T A n et a i Ị V N U ]ournal o f Science, Earth Sciences 28 (2012) 153-159

routes also play an im portant role in the process

causing floods 1A N ational Road w ith a height

o f 1.5-2m runs parallel to the sea, n a ư o w

drainage aperture form ed dam s prevent flood

large parts o f the w estern plains units flooding

in rainy season this is clear in the historic floods

o f 1999: in many roads, flood who breached

them to make escape routes flood erosion

principle backw ards for geophysics online form

located perpendicular to the direction o f spread

transmission o f the flood

In addition to the above factors affecting

areas dow nsừeam is influenced by tides, stoư n

surges W hen flood to m eet surges, or surges

will reduce downsfream flood w ater surface

slope, the ability to drain the sea slow ed dow n,

leading to rising flood w ater levels than norm al

At low tide, the w ater surface slope as well as

the flood flow rate increases, the m om ent the

am ount o f flood w ater to drain faster, and the

destructive pow er o f ửìe flood flow is also m ore

dangerous - large flow rate will be w ashed

away many houses, projects, river bank erosion,

etc All o f these features need to be included in

the flood and disaster prevention plans, rescue

scenario locally

3 Conclusion

1 Research area, Thua Thien Hue delta is

always potential risk o f flooding due to the

natural geographical conditions w ith specific

characteristics o f ửie region, especially the

m orphological characteristics o f the topography

associated with the arising in the process (ie the

form directly and objectively reflect the

operation o f flood and w aterlogging)

2 The w eather that caused flooding, storm ,

ữopical depression, tropical convergence zone

(single operation or in com bination w ith cold

air m asses) T h at is the reaso n for the Thua

T hien H ue d elta annual rainfall depending on the typ e o f the h ig h e st in the counữ y, but unev enly distribu ted , m ain ly in the rainy

m onths, so floo din g w as b o m v ery intense The distrib ution o f rainfall in space and tim e flood are very com plex, creatin g floods have m assive changes in the n atu re and in each section o f the riv er and its tribu taries F lood flow w ith great speed, w hile the plain is a narrow , iow-lying areas, close to the fo othills o f the m ountain, it is blocked from th e sea by a typical lagoon system , the focusing speed IS very rapid ly from

a n etw o rk o f sh ort riv ers and sư eam s, the average slope derived from the m ountains and foothills to the W est In this context, the flow rate is u sually v ery large, w hen ro lled dow n’ve created large an d rap id ly rising w ater, causing serious flooding

3 W e can n o t co m p letely allelopathic natural d isasters in general and flood disasters

in the reg io n in p articu lar, bu t can be active in the w ork o f early w arn in g (ie w arns practical areas w ill be flooded w ith tim e and depth o f flooding vary acco rd in g to geographical location and the w eath e r is rainy different flood), p rev en tio n an d resp onse, efficient

su pp ort for search and rescue w ork to reduce low m ost dam age to p eo p le an d the flood disaster o ccm red

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