Floods in Bangladesh : history, dynamics, and rethinking the role of the himalayas

There is no statistical evidence that the frequency of flooding in Bangladesh has increased during the 20th century. There is indication however, that the inter-annual variation of floods and the areal extent of big events have increased since 1950. Is it really true that deforestation and land use practices of the Himalayan farmers are to blame for the recurring and devastating monsoon floods in the plains of the Ganga and Brahmaputra? This book presents new evidence resulting from a research project on floods in Bangladesh in the context of highland-lowland linkages.--Publisher's description. Floods in Bangladesh: History, dynamics and rethinking the role of the Himalayas......Page 4 Contents......Page 6 Figures......Page 8 Tables......Page 15 Boxes......Page 18 Preface......Page 20 The core institutions (Table P.1)......Page 21 The key institutions for data collection (Table P.2)......Page 24 Partner institutions and resource persons for information exchange (Table P.3)......Page 25 Acknowledgements......Page 31 1.1. The theory of Himalayan degradation: Traditional understanding and emerging doubts......Page 32 1.2. The highlands - and their lowland linkages: Twelve years of research on Himalayan ecology......Page 34 1.3. The lowlands - and their highland linkages: Research on ‘‘Floods in Bangladesh’’......Page 35 1.4. The structure of the book......Page 40 1.5. An important contribution to the International Year of Mountains......Page 41 2.1. Bangladesh: An unusual country profile (see front cover)......Page 42 2.2. Mechanisms of the monsoon circulation......Page 48 2.2.1. The monsoon and its formation......Page 49 2.2.2. The cycle of the Indian summer monsoon......Page 52 2.2.4. Precipitation patterns in the Ganga-Brahmaputra-Meghna basin......Page 53 2.2.5. River discharge patterns in the Ganga-Brahmaputra-Meghna basin......Page 56 2.3.1. The main physiographical units......Page 58 2.3.3. The extent and range of flooding......Page 61 2.3.4. The depth, duration and timing of flooding......Page 65 2.3.5. The causes of flooding......Page 68 3.1. Rainfall......Page 70 3.2. Discharge......Page 76 3.4. Groundwater......Page 80 3.6. Reflection on the data situation......Page 82 4.1. Introduction to the issue......Page 83 4.2.1. A brief look at the longer-term geological history......Page 87 4.2.2. The last 20,000 years......Page 89 4.3.1. Historical floods in the Ganga and Brahmaputra catchments......Page 94 4.3.2. Specific flood events in Bengal in the eighteenth and nineteenth centuries......Page 96 4.4. The twentieth century......Page 100 4.4.1. Floods in Bangladesh, 1890-2004......Page 101 4.4.2. Flood history in the lowlands of the Ganga and Brahmaputra, 1954-1994......Page 109 4.4.3. Rainfall trends in the Ganga-Brahmaputra-Meghna basin in the twentieth century......Page 117 4.4.4. Discharge trends in the Ganga-Brahmaputra-Meghna basin in the twentieth century......Page 122 4.4.5. Increasing vulnerability: The socio-economic dimension......Page 130 4.5. The main findings......Page 137 5.1. Introduction......Page 139 5.2.1. Delimitation of subcatchments (step 1)......Page 143 5.2.2. Definition of inner-annual time periods (step 2)......Page 145 5.2.3. Calculation of areal precipitation and precipitation volume for the 13 subcatchments (step 3)......Page 147 5.2.4. Potential runoff (step 4)......Page 152 5.2.5. The relevance of the potential runoff for Bangladesh (step 5)......Page 168 5.2.6. Gaining experience with the newly introduced variables......Page 174 5.3. Introduction to the case studies......Page 178 5.4. 1906: A ‘‘flood year’’......Page 181 5.5. 1910: A ‘‘flood year’’......Page 185 5.6. 1922: A ‘‘flood year’’......Page 190 5.7. 1955: A ‘‘flood year’’ for Bangladesh......Page 194 5.8. 1974: A ‘‘flood year’’ for Bangladesh......Page 196 5.9. 1987: A ‘‘flood year’’ for Bangladesh......Page 203 5.10. 1988: A ‘‘flood year’’ for Bangladesh......Page 208 5.11. 1998: A ‘‘flood year’’ for Bangladesh......Page 214 5.12. 1923: A ‘‘dry year’’......Page 219 5.13. 1978: A ‘‘dry year’’ for Bangladesh......Page 222 5.14. 1993: An ‘‘average flood year’’ for Bangladesh......Page 226 5.15. The application of remote sensing techniques for the analysis of floods......Page 228 5.15.1. The database......Page 229 5.15.2. Classification of clouds and image-processing......Page 230 5.15.3. The test period 28 July-20 August 1987 (24 days)......Page 232 5.15.4. The test period 1-20 July 1988 (20 days)......Page 235 5.15.5. The test period 20 August-5 September 1988 (17 days)......Page 237 5.15.6. Summary......Page 240 5.16. The 11 case studies: A comparison......Page 241 5.16.1. Mid-August - a critical time for the development of large floods......Page 242 5.16.2. The hydro-meteorological patterns in the Ganga-Brahmaputra-Meghna system: A differentiated picture......Page 244 5.16.4. Synchronization of discharge peaks - a very important trigger for flood generation......Page 247 Notes......Page 252 The 1906 flood situation at a glance......Page 253 Hydrological contributions from the different subcatchments and their relevance (Figure 5A.2, Figure 5.1)......Page 255 Daily rainfall (Figure 5A.3)......Page 260 Summary......Page 264 The 1910 flood situation at a glance......Page 267 Hydrological contributions from the different subcatchments and their relevance (Figure 5A.6, Figure 5.1)......Page 270 Daily rainfall (Figure 5A.7)......Page 271 Daily water level (Figure 5A.8)......Page 273 Summary......Page 275 The 1922 flood situation at a glance......Page 276 Hydrological contributions from the different subcatchments and their relevance (Figure 5A.10, Figure 5.1)......Page 279 Daily rainfall (Figure 5A.11)......Page 282 Daily water level (Figure 5A.12)......Page 283 Summary......Page 284 The 1955 flood situation at a glance......Page 285 Hydrological contributions from the different subcatchments and their relevance (Figure 5A.14, Figure 5.1)......Page 287 Daily rainfall (Figure 5A.16)......Page 289 Summary......Page 292 The 1974 flood situation at a glance......Page 294 Hydrological contributions from the different subcatchments and their relevance (Figure 5A.19, Figure 5.1)......Page 296 Monthly discharge (Figure 5A.20)......Page 298 Daily rainfall (Figure 5A.21)......Page 300 Daily discharge (Figure 5A.22)......Page 302 Groundwater (Figure 5A.23)......Page 304 Summary......Page 307 The 1987 flood situation at a glance......Page 308 Hydrological contributions from the different subcatchments and their relevance (Figure 5A.25, Figure 5.1)......Page 310 Monthly discharge (Figure 5A.26)......Page 313 Daily rainfall (Figure 5A.27)......Page 315 Daily discharge (Figures 5A.28 and 5A.29)......Page 318 Groundwater (Figure 5A.30)......Page 322 Summary......Page 324 The 1988 flood situation at a glance......Page 325 Hydrological contributions from the different subcatchments and their relevance (Figure 5A.32, Figure 5.1)......Page 328 Monthly discharge (Figure 5A.33)......Page 330 Daily rainfall (Figure 5A.34)......Page 332 Daily discharge (Figures 5A.35 and 5A.36)......Page 336 Tidal effects (Figure 5A.38)......Page 340 Summary......Page 343 The 1998 flood situation at a glance......Page 344 Monthly rainfall (Figure 5A.40, Table 5A.7)......Page 350 Daily rainfall (Figure 5A.41)......Page 352 Daily water level......Page 354 Summary......Page 360 The 1923 drought and flood situation at a glance......Page 361 Hydrological contributions from the different subcatchments and their relevance (Figure 5A.44, Figure 5.1)......Page 362 Daily water level (Figure 5A.46)......Page 364 The 1978 drought and flood situation at a glance......Page 367 Hydrological contributions from the different subcatchments and their relevance (Figure 5A.47, Figure 5.1)......Page 368 Monthly discharge (Figure 5A.48)......Page 370 Daily discharge (Figure 5A.50)......Page 373 The flooding in the Indian Ganga basin......Page 375 Summary......Page 379 The 1993 flood situation......Page 381 Monthly rainfall (Figure 5A.53)......Page 382 Daily rainfall......Page 383 Daily discharge......Page 385 Summary......Page 388 6.1. The data situation......Page 390 6.2. The geological and historical dimension......Page 392 6.3.1. Mass movements......Page 394 6.3.2. Soil erosion......Page 397 6.4.1. Shifting river courses and lateral erosion......Page 405 6.4.2. Sediment load and sedimentation......Page 408 7.1. Introduction: Why should the human dimension be considered in a flood research project?......Page 420 7.2. The fieldwork: How was the human dimension approached in this flood research project?......Page 421 7.3.1. Flood perceptions of the affected rural population......Page 424 7.3.2. Flood perceptions of politicians and engineers......Page 427 7.3.3. Floods in the perception of the international media......Page 428 7.4. Flood events: Adaptation and mitigation strategies of the rural population......Page 430 7.4.2. Agriculture and crops......Page 431 7.4.3. Daily life......Page 433 7.4.4. Transportation......Page 434 7.5.1. Perceptions and experiences......Page 435 7.5.2. Coping strategies......Page 437 7.6.1. Approaches before 1989......Page 441 7.6.2. The Flood Action Plan (FAP), 1989-1995......Page 443 7.6.3. 1995 and beyond......Page 444 7.7. The approach of the rural population to flood control and flood protection......Page 449 8.1. The history of floods in Bangladesh......Page 454 8.2. The dynamics of floods in Bangladesh......Page 455 8.2.1. The regional dimension......Page 456 8.2.3. The process-oriented dimension......Page 457 8.3. Rethinking the role of the Himalayas......Page 458 8.4. Natural disasters and their impacts - A brief comparison......Page 459 8.5. Different perceptions, integrated approaches and common solutions......Page 461 8.6. A short comparison with recent processes in three floodplains of three continents......Page 462 8.7. A brief outlook: Research, development and cooperation......Page 465 8.7.1. Research and cooperation......Page 466 8.7.2. Development and cooperation......Page 467 References......Page 469 Index......Page 491

Deforestation and land use practices of Himalayan farmers are commonly blamed for the recurring, devastating monsoon floods in the plains of the Ganges and Brahmaputra. Floods in Bangladesh presents new evidence to disprove this long-held assertion.

This book demonstrates that the hydro-meteorological processes in the Himalayas are not the main causes for the floods in Bangladesh. The combination of simultaneous discharge peaks of the big rivers, high runoff from the Meghalaya Hills, heavy rainfall, high groundwater tables, and spring tides creates particularly favorable conditions for large-scale flooding. Accordingly, the myth about deforestation creating big floods and the habit of blaming mountain dwellers for the flood catastrophes must be abandoned.

Deforestation and land use practices of Himalayan farmers are commonly blamed for the recurring, devastating monsoon floods in the plains of the Ganges and Brahmaputra. Floods in Bangladesh presents new evidence to disprove this long-held assertion. This book demonstrates that the hydro-meteorological processes in the Himalayas are not the main causes for the floods in Bangladesh. The combination of simultaneous discharge peaks of the big rivers, high runoff from the Meghalaya Hills, heavy rainfall, high groundwater tables, and spring tides creates particularly favorable conditions for large-scale flooding. Accordingly, the myth about deforestation creating big floods and the habit of blaming mountain dwellers for the flood catastrophes must be abandoned. Deforestation and land use practices of Himalayan farmers are commonly blamed for the recurring, devastating monsoon floods in the plains of the Ganges and Brahmaputra. This work presents evidence to disprove this long-held assertion.