Cyclone and Storm Surge - Iczmpwb.org

More documents

Recommendations

Info

2.46 The other type of failure may occur due to reasons like the presence of excess pore pressure generated by a quick falling river water level. When a bank fails in this kind of geotechnical mode, the probable slip lines or slip circles may be predicted, which depends also upon the type of material forming the banks. 2.7.2. Embankments/dykes and their failures Agriculture is carried behind the nearly 3500 Kilometer of protective earthen embankments. Those are constructed by local earth of surface layers which consist mostly of very fine coherent. It is generally of low liquid limit. This soil has got the property of low erosion resistance because this material becomes liquid in coming with contact with water. Previously a forest belt of minimum width of 100 meter was kept as Foreshore land in aligning on the embankment for the purpose of damping the wave action. But by this time the increase of population and want of fuel has caused unregulated felling and now practically there is no protection to embankment from high waves and suiting currents. These dykes were originally constructed by the Latdars with the gradual rise of high water level over the years; the Latdars increased the height of the dykes correspondingly. The constant erosion of the soil due to wave wash was also attended by them. But since late forties of this century the Latdars started neglecting the maintenance due to rise in labour cost as well as the apprehension of imminent state purchase of the Latdar's interest. The dykes at the time of taking over by the Irrigation Department in 1960 were found to have inadequate section and strength. Breaches and overtopping was of quite common phenomenon. Due to paucity of funds, this enormous length of embankments could not furthermore be brought to adequate section and height to ensure safety. In many cases these dykes are aligned bordering the scouring bank of meandering rivers. This necessitated another set of embankments, some dist inland, called the retiring embankments. Generally during flow tide accompanied strong southerly wind from second fortnight, of March, to October, the river water splashes over the earthen embankment causing continuous erosion of soil. This phenomenon occurs twice a day and the poor soil give very little resistance to it. On an average two major tropical cyclonic storms occur in each year in Sundarbans. During such cyclone storms high waves are generated in sea face and which attack on the embankments at great storm velocities and thus overtop embankment without free board, erode river side slope and crest and cause breach. For want of cover protection works (Brick or Brick Block Revetment works) in strength of vulnerable zone, the breach cannot be prevented.
2.47 As such, since most of the embankments have been constructed by many years before by not so scientific methods, the failures of these is no surprise, especially if these do not have adequate gradient on the river side or on the land side. Further, even if these are well constructed, the gradual undercutting of the riverbank may lead to weakening of the foundation of these embankments leading to a sudden collapse. If the embankments do not have adequate face pitching, there is a high chance of these getting eroded away by the impact of lashing waves generated in the ocean or the rivers due to cyclonic storms (Figure 2-12). Figure 2-12. Embankment failure due to wave dash It may also be possible that the embankment protection in the form of brick pitching may not be strong enough at places to bear the wave dash, leading to exposure of the river side bank and consequent erosion. A study by Hazra (2006) comparing the earlier maps of the Sundarbans and present day satellite imageries has inferred important statistics about the vulnerability of the islands in the region due to cyclonic effects. The researcher and his team had calculated the length of the embankments from Survey of India Topographic sheets (No.79B/4, 79B/8, 79B11, 79B/12,79B/ 16, 79C/1, 79C/2, 79C/5, 79C/6, 79C/9, 79C/10, 79C/13, 79C/14, of 1969). The embankments were then digitized and length calculated, which was found to be around 3110.33 Km. Comparing this with the recent IRS 1D LISS III and PAN data of 2001, it was found out that some parts of the embankments have already been washed out by cyclones and erosion. It has also been inferred that due to high rate of siltation on the
Page 2 and 3:
HAZARD ASSESSMENT AND DISASTER MITI
Page 4 and 5:
Project Team Though the outcome of
Page 6 and 7: Preamble The State of West Bengal,
Page 8 and 9: 1.2 IMD, in its website (http://www
Page 10 and 11: 1.4 5. Proposals for location of cy
Page 12 and 13: 2.2 region is that which struck the
Page 14 and 15: 2.4 Figure 2-2. Track of the 1970 B
Page 16 and 17: 2.6 The most destructive element as
Page 18 and 19: 2.8 the two regions is rather diffe
Page 20 and 21: 2.10 2.4. The eastern coastal zone
Page 22 and 23: 2.12 velocity is first checked. As
Page 24 and 25: 2.14 Strong winds known as cyclones
Page 26 and 27: 2.16 2.4.6. Soil characteristics Th
Page 28 and 29: 2.18 All rivers have in general sou
Page 30 and 31: 2.20 Another interesting feature of
Page 32 and 33: 2.22 formed does not pose so much o
Page 34 and 35: 2.24 2.4.11. Forest composition The
Page 36 and 37: 2.26 Canning (Bidyadhari Outfall in
Page 38 and 39: 2.28 Administrative information Pop
Page 40 and 41: 2.30 Mangrove plantation beyond the
Page 42 and 43: 2.32 A retired embankment of river
Page 44 and 45: 2.34 The beaches are flattened by s
Page 46 and 47: 2.36 of a doiminant tidalbasin of t
Page 48 and 49: 2.38 primary mode is centered on th
Page 50 and 51: 2.40 Aquaculture ponds located betw
Page 52 and 53: 2.42 All the islands are situated w
Page 54 and 55: 2.44 • Transport the water to the
Page 58 and 59: 2.48 channel floor, some of the riv
Page 60 and 61: 2.50 embankments. Crops and propert
Page 62 and 63: 2.52 2. To reduce the average dista
Page 64 and 65: 3.2 a storm surge caused by a tropi
Page 66 and 67: 3.4 these merchants may have been t
Page 68 and 69: 3.6 Figure 3-1. Map of India during
Page 70 and 71: 3.8 larger volume of sewage and dra
Page 72 and 73: 3.10 receive, at least during the r
Page 74 and 75: 3.12 3.9. Drainage scheme of Dr. B.
Page 76 and 77: 3.14 3.10. CMPO and KMDA (originall
Page 78 and 79: 3.16 Flows are diverted to the loca
Page 80 and 81: 3.18 the Bhangar region through the
Page 82 and 83: 3.20 the ocean level as a result of
Page 84 and 85: 3.22 Table 3-6. Major pumping stati
Page 86 and 87: 3.24 Table 3-9. Drainage basin area
Page 88 and 89: 3.26 will lead to significant impro
Page 90 and 91: 3.28 locks, one at Chitpur and anot
Page 92 and 93: 3.30 Respectively. The discharge of
Page 94 and 95: 3.32 Figure 3-6. The downstream of
Page 96 and 97: 3.34 Figure 3-10 shows the tail end
Page 98 and 99: 3.36
Page 100 and 101: 3.38
Page 102 and 103: 4.2 In US, there is a steady decrea
Page 104 and 105: 4.4 This shows that Orissa (with 10
Page 106 and 107:
4.6 30 25 20 15 10 Severe Cyclone C
Page 108 and 109:
4.8 Table 3: Return periods of cycl
Page 110 and 111:
4.10 Table 5: The number and return
Page 112 and 113:
4.12 work station (the Automated Tr
Page 114 and 115:
4.14 through this trough into the d
Page 116 and 117:
4.16 Mean Low water 1.51 1.39 1.34
Page 118 and 119:
4.18 τx,τy : x and y components o
Page 120 and 121:
4.20 formulation. However, the rete
Page 122 and 123:
4.22 ∂u ~ ∂ ~ ~ ∂ ~ ~ ∂ζ 1
Page 124 and 125:
4.24 Δ p p(r) = p( ∞) − [1+ (r
Page 126 and 127:
4.26 maximum surge for this event w
Page 128 and 129:
4.28 U-Component of Velocity (Surfa
Page 130 and 131:
4.30 ## ## ## #### ### ## ########
Page 132 and 133:
4.32 V-component of Velocity (Surfa
Page 134 and 135:
4.34 U-component of Velocity (Surfa
Page 136 and 137:
## ################################
Page 138 and 139:
4.38 V-Component of velocity (Surfa
Page 140 and 141:
5.2 particular human settlement to
Page 142 and 143:
5.4 The Composite Vulnerability Ind
Page 144 and 145:
5.6 (2004 prices) prevalent in dist
Page 146 and 147:
5.8 Moyna 0.6280 0.1592 0.542286 0.
Page 148 and 149:
5.10 5.4.2. Social infrastructure H
Page 150 and 151:
5.12 Budge-Budge(Part-II) 0.0000 0.
Page 152 and 153:
5.14 secondary and tertiary activit
Page 154 and 155:
5.16 F i Fˆ i ⎛ Total no. of =
Page 156 and 157:
5.18 Table 5-4: Composite Index of
Page 158 and 159:
5.20 M ′ = H M ′′ = I . S whe
Page 160 and 161:
Chapter Six Mitigation Strategies a
Page 162 and 163:
6.3 Beside these differences in lev
Page 164 and 165:
6.5 • to reduce the destructive f
Page 166 and 167:
6.7 6.2.4. Methods of Construction
Page 168 and 169:
6.9 is attached to the structure. T
Page 170 and 171:
6.11 (b) Medium rivers to armour th
Page 172 and 173:
6.13 Likewise, in all the embankmen
Page 174 and 175:
6.15 Figure 6 -5 Figure 6 -6 Figure
Page 176 and 177:
6.17 Benefit cost ratio Area benefi
Page 178 and 179:
6.19 Location and cost of proposed
Page 180 and 181:
6.21 Swaraupnagar Swaraupnagar 100
Page 182 and 183:
6.23 Gobadia Kakdwip Dk Kasiabad &
Page 184 and 185:
6.25 Location and cost of proposed
Page 186 and 187:
6.27 " Jagaddal " 800 6400000 " Jag
Page 188 and 189:
6.29
Page 190 and 191:
6.31
Page 192 and 193:
6.33
Page 194 and 195:
6.35 Figure 6 -11 Figure 6 -12
Page 196 and 197:
6.37 Figure 6 -15 Figure 6 -16
Page 198 and 199:
6.39 Figure 6 -19 6.2.7. Recommenda
Page 200 and 201:
6.41 4. Rajraj Swarup & Ramnagar Ab
Page 202 and 203:
6.43 project. Such sediment deficit
Page 204 and 205:
6.45 paludosa, Rhizophora apiculata
Page 206 and 207:
6.47 15. Ceriops tagal 0.22 0.40 0.
Page 208 and 209:
6.49 shelterbelt (average 100 m wid
Page 210 and 211:
6.51 (assuming land acquisition cos
Page 212 and 213:
6.53 location are missing reducing
Page 214 and 215:
7.2 resulted in large scale waterlo
Page 216 and 217:
7.4 5. No adverse effect in drainin
Page 218 and 219:
7.6 15 LT Panel L.S. 2,200,000 16 I
Page 220 and 221:
7.8 Bagjola, Kestopur and SWF chann
Page 222 and 223:
Executive Cost Summary of Recommend
Page 224 and 225:
References Kanjilal (2005) “Sunde
Page 239:
“……………….Designingadis
show all

Cyclone and Storm Surge - Iczmpwb.org

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?