FLOOD AND FLASH FLOOD ANALYSIS FOR BARTIN RIVER BASIN

FLOOD AND FLASH FLOOD ANALYSIS
FOR BARTIN RIVER BASIN
Associate Professor Hüseyin TUROĞLU
Istanbul Universty, Department of Geography
Ordu Cad. No:196
34459 Laleli, ISTANBUL
[email protected]
ABSTRACT
Largely damaged and injurious floods and flash floods of which frequency and
strength features gradually show an increase, come into existence in city center of
Bartın City. In this study, we are aiming to analyse floods and flash floods which
cause weighty damages on this region’s and Turkish economics. For this aim, Bartın
River’s Basin has been taken as scope of this study. In connection with analysis of
floods and flash floods, data belongs to physical geography features of Bartın River’s
Basin and also faulty varieties and choices have been used. Analysis studies have
been implemented by means of Geographical Information Systems and Remote
Sensing Technologies and also satelite images and topographical maps in different
scales have been used. Data obtained by means of this analysis demonstrates that
geopraphical features of Bartın River’s Basin has very adequate conditions for
natural disasters such as floods and flash floods, therefore it also shows that
increasing of their frequencies and strengths and turning into forms of natural
disasters are taken root from faults arisen of utilization choices and types on the land.
Digital Database Bed Layers belong to geographical features of Bartın River’s Basin
has been overlaid by flood, flash flood classifications and concerning flood, flash
flood risk maps were prepared.
Keywords: Bartın River, flood and flash flood, Geographical features, Geographic Information System.
INTRODUCTİON
Natural disasters such as floods and flash floods of which frequency and
strength features show an increase year by year, occur and affect Bartın City (Fig.1).
These hydrographic originated nautral disasters cause serious and weighty damages
on Turkish economics as well as local people. A great deal of studies with different
standpoints were investigated on floods and flash floods happen in Bartın City
(Şorman, vd., 1998, Turoğlu, vd., 2004, Tüysüz, vd., 2004, Turoğlu, 2005). Within the
context of this research we approached the matter from a standpoint of geographical
perpective and aimed to analyse happened floods and flash floods based on Bartın
River’s Basin.
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INTERNATIONAL CONGRESS ON RIVER BASIN MANAGEMENT
In the course of this research, office studies and fieldworks have been
implemented jointly. In the scope of office studies, forming of digital database,
analysis of places and visualisation of results have been implemented and during
fieldworks also applications such as measurement, analysis results and testing of
prepared maps were realized. In the course of these studies topographical and
geological maps in scales of 1/25.000, air photos in scales of 1/35.000 belongs to the
years of 1944 and 1998, Landsat 1975 MSS, 1987 TM satellite images, Bartın City’s
building development scheme in a scale of 1/5.000, all in all have been used as a
database. Analysis studies were implemented by means of Geographical Information
System and Remote Sensing Technologies.
Floods and flash floods cause damages in city center of Bartın City are actually
natural events orientated by physical and human geographical features of Bartın
River’s Basin. Transformation of such natural events into natural disasters is a result
of efficiency of humankind factor. For the aim of flood and flash flood analysis, it is
planned to analyse such events by means of obtained database belongs to
geographical characteristics of that basin. It is a preferential method to implement
related studies and investigations on the media of Geographical Information Systems
because of its advantages on data diversity and analysis opportunities (Knighton,
1996, Sarma, 1999, Gren, 2000, Hansson ve Ekenberg, 2002, Ekenberg, vd., 2003,
Turner-Gillespie, vd., 2003, Turoğlu, vd., 2004, Turoğlu, 2005).
Fig. 1: Digital Elivation Model of Bartın River’s Basin.
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RIVER BASIN FLOOD MANAGEMENT
Database and Analysis
As geographical factors act a part on happening of natural disasters arisen from
hydrographic origin, in the scope of physical geography the field’s geomorphological
(slope, aspect), lithological, climatological, hydrographical, plant and soil
characteristics have been investigated and also in the scope of human geography;
population and settling area of the basin, economical activities and field usage
characteristics were studied (Fig. 2).
BARTIN RIVER’S BASIN
Slope
Aspect
Drainage
Network
Climate
Soil
Weathering
Permeability
Rocks
Structure
Shape index
Drainage pattern
Drainage density
Riverbed
N, E, S, W
NW, NE, SE, SW
Flat
Lithology
Precipitation
Temparature
Wind
Moisture
Vegetation
Land Use
Forest area
Destroyed forest
Shrubs
Grasslands
Infiltrate
Moisture
Temparature
Structure
Texture
Water holding
capacity
percolation
Settlement
Farming
Vegetation
Harbour
Changing of
drainage network
Fig. 2: Database contents for Flood and flash flood in Bartın River Basin.
Within the context of geomorphological features; slope and aspect characteristics
of Bartın River’s Basin have been classified in connection with flood and flash flood.
Four slope classes have been distinguished. The slope value which holds the widest
area is < 15% and it is described as perpendicular class (57,13%). The second slope
which holds the second widest area is 0-2 % and this class is described as flat and
hole areas (21,06%). Within the first class, floods and flowings are more effective and
within the second class of slope, inundations are more influential. Total value of
these two slope classes represent 78,19% of Bartın River’s Basin.
Hillsides in directions of NE, N, NW and W are slopes which have short
sunbathing times, weak sunbathing strengths, high cloudy situations, high humidity
rates and low evaporations. Due to such characteristics, loss rate on surface flowing
water amount is very low. These hillsides cover 41,48% of total area of the basin. Flat
areas on which inundations play a part, cover almost a half of the remained area of
the basin (24,54%).
Hydrographic features which are parameters of physical geography of study
area have much importance for sheet flood, torrent and flood disasters. Results of
analysis of morphometric and slope features of Bartın River have shown a severly
increasing character (Fig. 3).
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INTERNATIONAL CONGRESS ON RIVER BASIN MANAGEMENT
Fig. 3: Subbasins of Bartın River’s Basin and drainage network features.
Climatic features of Bartın River’s Basin have been studied as precipitation, heat,
wind and atmospheric moisture. Result of this study has been appeared that max.
heats in July and August, max. precipitation as rain in September-November period,
max. rain-fall caused natural disasters as strong rain-storms in May-July period
(Table 1). The basin is usually effected from northerly winds but violent winds are
effected from southwesterly with strong rain-storms (Fig. 4). Also, high atmospheric
moisture attracts attention as one of the climatic components in Bartın River basin.
Table 1:Ditribution of monthly precipitation(m2/kg) in Bartın River’s Basin(D.M.İ.G.M, 2001).
Year/
1
2
3
4
5
6
7
8
9
10
11
12
To-
1990
76
51
37
70
74
43
72
15
181
86
36
135
876
1991
67
12
34
80
91
214
90
50
204
139
49
113
1143
1992
78
104
61
57
21
157
65
11
48
121
152
162
1037
1993
93
72
44
31
52
32
27
99
42
16
104
90
702
1994
81
18
32
32
43
43
1
64
13
151
238
179
895
1995
130
37
97
70
19
147
164
76
120
123
243
94
1320
1996
55
60
65
67
33
57
13
82
264
173
20
160
1049
1997
68
112
84
106
26
56
148
260
34
158
46
114
1212
1998
125
134
116
40
220
15
84
1
173
158
74
95
1235
1999
62
129
58
19
41
172
14
99
45
114
204
64
1021
2000
155
77
130
78
39
175
12
247
148
146
2
115
1324
ORT.
90
73,27
68,91
59,09
59,91
101
62,73
91,27
115,6
125,9
106,2
120,1
1074
Mounth
tal
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RIVER BASIN FLOOD MANAGEMENT
N
23
N
NNW
1800
NNE
1600
1400
NW
22
WN
NE
NE
21
1200
20
1000
800
WNW
19
ENE
600
400
18
200
W
0
E
WSW
W
17
E
ESE
SW
SE
SSW
SW
SE
SSE
S
S
Fig. 4 : Frequent and strong winds directions in Bartın River’s Basin.
Mesozoic and Tertiary deposit units which are of thin grain structure and shelf
deposits have been most widespread lithological unit of study area. Paleozoic metamorphic carbonate rocks appear in limited areas taking place in connection with
Blacksea of Bartın River and its vicinity in basin. Quaternary sediments are widespread as fluvial precipitate forms in slope breaking, bed of Bartın River and vicinity.
Four different soil types which are podsolic soils, without lime brown forest
soil, brown forest soil and alluvial soil have been classified in basin. Almost all types
of soils in the basin are of fine grain, impermeable and low infiltration capacity.
It has been understood that devastate of natural vegetation of basin according to
investigation of formerly documents. Actual forest area has been calculated as 34,7
percentage of Bartın River’s Basin through Remote Sensing studies, fieldworks and
other documents belonging to vegetation features of basin.
Significant changes on field usage of Bartın River’s Basin has been realized
within the time period starting from 1944 till today. It is possible to classify such
changes as settlings, agricultural areas, flora, port and drainage changes. In general
there was scattered settlement on hillsides 60 year ago, but housings have been
amassed on river beds in the time period of last 10 years. For instance whereas Bartın
City’s center had an area of 0,5355 km2 in 1944, as a result of area measurements
obtained from 2003 dated satellite images it has been concluded that city center of
Bartın City became 16,2762 km2 and this expansion was realized within flood and
flash flood areas. Usage of agricultural areas for settling reasons and rapid
destruction of natural flora are most significant changes on area utilization.
Construction of Bartın City Port, due to taking no notice of region’s climatic and
drainage system characteristics, acts a very effective role on flood and flash flood
events. By means of port construction, Bartın River has been canalized in order to be
discharged in SW direction. But turbulent-stormy air masses which carry rainfall are
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INTERNATIONAL CONGRESS ON RIVER BASIN MANAGEMENT
in SW direction (Fig.4). Therefore this situation causes Bartın River which has 0,2%
bed slope to inundate sea water course in boisterous weathers and it prevents
discharge of Bartın River into the sea (Photo 1).
Photo 1: Drainage network of Bartın River has been changed in basin.
Changing for harbour construction was being most tragic.
Because of artificial or natural filling, cross-section of Bartın River chanel have
shrinked and water carrying capasity has became less then before. New
circumstances have been effecting as increasing character on frequency and intensity
of floods and flash floods in Bartın River Basin (Photo 2).
Photo 2: Artificial filling cause to shrink of cross-section in the Bartın River channels.
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RIVER BASIN FLOOD MANAGEMENT
CONCLUSİON :
Flood and flash flood analysis of Bartın River Basin have been realized using
geographic parameters of basin and obtained data have been summarized on Table 2.
Also, flood and flash flood risk maps of Bartın River Basin have been produced
according to data base (Fig. 5-6). The results taking place natural disasters such as
sheet flood, flash flood and flood analyses is listed below.
♦ Too much water excising of caring capacity of riverbed bring about to
natural disasters.
♦ This water is supplied from heavy rainstorm of frontal and orographic
origin.
♦ Heavy rainstorms are affected together with strong SW winds.
♦ Geologic and geomorphologic features of Bartın River basin show
encouraging features to natural disasters.
♦ Both water absorption capacity of basin and water loss due to surface
flooding is very poor.
♦ Drainage system of basin, size and rate of flow features; subbasin
characteristics encourage torrent and floods.
♦ Causes to hydrographic natural disasters which result in miss of land use
types in harmonizing land potential are preferred by man is very important.
♦ Highest risk rate of each type of natural disasters such as sheet flood,
torrent, flood, erosion and mass-movement is brought about 20-40 percent in
the basin.
♦ 19,02 percent of basin is under the highest risk of disaster rate.
♦ It is calculated that only 6,77 percent of basin have without natural disaster
menace.
♦ Influenced area by means of hydrographic origin disasters such as torrents
and floods has been covering 8298255,02 m2 and 50, 98 percentage in Bartın
city. Torrent and flood safe areas cover 7977904,66 m2 and 49, 02
percentage in Bartın city
♦ According to results of analysis, Unuseful areas having flash flood and flood
risks for settlement cover 38.19 percentage of Bartın city.
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Table 2: Table showing the main geographic factors and characteristics having important role
for flood and flash flood in Bartın River Basin.
Geograp
hic
Factors
Slope
Characteristics
Description
Impact on disaster
Disater
%0–2
Low land, Level,
Nearly level
Strong water flow, big water body, ponding
Inundation, flood
%2–5
Very gentle slope
Strong water flow, water collection,
Flood,
Flash flood
% 5 – 15
Gentle slope
Strong water flow, water collection,
Flash flood, sheet
flood
% 15 <
Steep slope
Less sunlight for big part of basin, High moisture, less
evaporation
Flood,
flash flood, sheet
flood
Strong water flow, water collection,
Inundation, Flood
41,48%
NE, N, NW, W,
Aspect
E, SE, S, SW
Flat
Shape index
Drainag
e
Network
Climate
Dendritic
Drainage density
D=ΣL/A= 0,96
Riverbed
Artificial filling
Precipitation
Heavy rainstorm
Wind (Stormy)
SW
Evaporation
Low
Weathering
Permeability
More water flowing surface
Water holding
capacity
More water flowing surface
Inundation, flood,
flash flood, sheet
flood
Less water missing but more water flowing surface
Inundation, flood,
flash flood, sheet
flood
Poor
Humid
Medium
Fine materials
Medium
34,70%
Vegetati
on
Land
Use
Inundation, flood,
flash flood, sheet
flood
Poor
Limeston, clay,
silt, sand
Structure
Unexpected and big mass water flowing surface
More debris for sediment yield
Structure
Heat
Inundation, flood,
flash flood, sheet
flood
Insufficient canal carring capacity
Strong
Rocks
Moisture level
Very usefull conditions for water collection
77 % (Average)
Sedimentary (90
%)
Infiltrate and
percolation
Soil
24,54%
Sw=L/W=1,01
Drainage pattern
Moisture
(Relative)
Litholog
y
33,98%
Forest
Less water keep, more water flowing surface
Destroyed forest
27,67%
Agricultural lands
36,00%
Settlement
1,62%
62,37%
Flood,
flash flood, sheet
flood
Inundation, flood
Vegetation
Farming
36,00%
Hinder to water flow
Owing to destroyed forest, suitable condition for flood, flash
flood and sheet flood.
Low slope, flats or sunken lands help water accumulate
Harbour
0,01%
Hinder to discharge of water to Black Sea
Inundation, flood,
flash flood, sheet
flood
RIVER BASIN FLOOD MANAGEMENT
Fig. 5: Flash flood risk map of Bartın River Basin.
Fig. 6: Flood and inundation risk map of Bartın River Basin.
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