uBfw/43/01 ADAPTATION TO DISASTER: HOUSING IN FLOOD PRONE AREAS WITH SPECIAL REFERENCE TO THE COLOMBO DISTRICT A dissertation presented to the Faculty of Architecture of the University of Moratuwa for the MSc. (Architecture) Examination May 2000 74105 7 2 . OO University of Moratuwa 7 2 . - OZLS 74105 A B S T R A C T Water is a precious commodity and considered a source of life. This life giving water appears as a common thread woven through the religion, literature and art of every culture. Architectural compositions too, are greatly enhanced by the use of water. Moreover, many of the worlds earliest civilization's originated in areas where water was readily available, such as in the Nile Delta and the Indus valley. Even in Sri Lanka, early human settlements were founded near sources of water such as the Malwatu Oya. Despite water's role as a common denominator for life, it also brings death and disaster with it when it floods, showing that too much water is as bad as too little. Flooding causes extensive damage to people and property and can be considered as the most widespread natural disaster which occurs in Sri Lanka. Flooding is common in many areas of the country and the district of Colombo also has this particular problem. However, one may be tempted to ask "Are there really floods in Colombo?" The answer is a definite "yes". One may not hear of great catastrophes related to floods within the Colombo district, but it nevertheless causes much damage to property and imposes hardships on the people when parts of the city and surrounding areas get flooded after intense rainfalls of even short duration. Therefore, it is imperative that mitigatory measures be taken in order to minimise the damaging effects of floods. In this regard, Architectural solutions for housing and building and proper planning procedures incorporating regulatory controls will ensure that people will have the opportunity of coping with and adapting to floods without mcurring loss or damage. A C K N O W L E D G M E N T Grateful acknowledgment is made to the following, for their assistance and guidance given to me, in connection with the preparation and successful completion of this dissertation; - Dr. L. S. R. Perera, Dr. R. Dayaratne and Dr. S. Manawadu, Senior lecturers attached to the Faculty of Architecture, for their patient and invaluable advice, inspiring discourses and constructive guidance in the preparation of the dissertation. - Archt. Anura Ratnavibhushana, who took time off from his busy schedule to give me information to be used in the preparation of this work. - Ms. Shirley Mattingly, Urban Risk Management Advisor attached to the Asian Disaster Preparedness Center, Thailand, and Ms. Lilianny Sigit of the Department of Architecture, Petra Christian University, Surabaya, Indonesia, who very kindly sent me information to be used in the preparation of this document. - Mrs. G. Karunaratne, Director, Center for Housing Planning and Building for her cordial advice and help in the preparation of this work. - Neranjana Karunaratne, my husband who assisted me in numerous ways in the preparation of this dissertation and for his unstinted help in the completion of it to meet requisite standards. iii Contents Page No Abstract ii Acknowledgment iii List of Illustrations vi Introduction 1 1 Disaster, man and his environment 6 1.1 Disaster: conceptual issues 6 f 1.2 Impacts of disaster - physical, psychological and social issues 8 1.3 Disaster and the built environment 11 1.4 Flooding and human settlements 12 1.4.1 Types of floods 12 1.4.2 Flood impacts on society 15 1.4.3 Impact of flooding on households 16 2 Impacts of floods in the Colombo district 20 2.1 Demographic parameters and environmental aspects 21 2.2 Present situation of floods in the Colombo the district 30 f 2.2.1 Colombo City - Ocean Front Area 35 2.2.2 Colombo Flood Detention areas and its catchment 42 2.2.3 Flood plains of the Kelani river 47 3 Adaptation to floods: Guidelines for human settlement planning 57 3.1 Flood Plain Zoning 57 3.2 Land use control and regulatory measures 58 3.3 Site selection and analysis 60 3.3.1 Flooding characteristics 62 3.3.2 Soil characteristics 63 3.3.3 Wind characteristics 64 4 Adaptation to floods : Guidelines for design and construction 9t of flood resistant housing 66 4.2 Site design 78 4.2.1 Site flooding characteristics 80 4.2.2 Access and egress 81 4.2.3 Vegetation 81 4.2.4 Flood water drainage and storage 82 iv 4.3 Building design 83 4.3.1 Aesthetic considerations 83 4.3.2 Configuration 84 4.4 Materials and Construction Techniques 85 4.4.1 Foundations 85 4.4.2 Services and mechanical equipment 89 4.4.3 Building materials 89 4.4.4 Glass protection 90 4.4.5 Breakaway walls 91 4.4.6 Retrofitting existing structures 91 Conclusions 93 Bibliography 95 Annexes 98 f v LIST O F I L L U S T R A T I O N S FIGURE N O . PAGE N O . 1. Map of Sri Lanka 21 2. Average annual rainfall 23 3. Shanties built on canal reservations 29 4. The 3 separate areas to be studied 34 5. Slums and shanties of Colombo 34 6. The growth of Colombo 38 7. Historic sector and Beira lake 39 8. Location of the Colombo Flood Detention Ares 42 9. Historical remains of the ancient city of Kotte 44 10. The lock-gates at the St. Sebastian canal 46 11. Reclamation of land for development 46 12. Location of Bunds on the Kelani river 48 13. Flooded houses on the banks of the Kelani river 51 14. Flooded houses under the Kelani bridge 51 15. Houses constructed on the Flood Protection Bunds 51 16. Houses constructed on the Flood Protection Bunds 51 17. House to be partially demolished 52 18. House - during floods 52 19. House - when there are no floods 52 20. Flooded roads 53 21. Flooded roads 53 22. House in danger of being washed away 53 23. Construction of groins 53 24. Floodplain zones 58 25 River walk 59 26. Hydrostatic forces 62 27. Hydrodynamic forces 63 28. Wind forces 64 29. Children playing outside Malay house on stilts 66 30. Panavitiya ambalama - constructed on top of boulders 67 31. Tampita viharaya - an elevated structure 67 vi 32. Grain storage - vee bissa 68 33. Villa Savoie at Poissy 68 34. Farnsworth House 69 35. Ferrocement floating house - Floor Pans & Side Elevation 71 36. Ferrocement floating house - Sections 72 37. Water Bungalow 73 38. Luxury town houses, Bridgeport, Connecticut - Birds eye view 74 39. Luxury town houses, Bridgeport, Connecticut - Site Layout & Section 75 40. Residential development, Charlestown, Rhode Island - Perspective 76 41. Residential development, Charlestown, Rhode Island - Section 77 42. Landscaping in site design 78 43. Landscaping in site design 79 44. Site design to reduce flood hazards 79 45. Building clusters dispersed throughout the site 80 46. Configurations 84 47. Orientation of rectangular buildings 84 48. Elevation by earth fill 86 49. Elevation by shear walls 87 50. Elevation by posts 87 51. Elevation by piles 88 52.. Elevation by piers 88 53. Shutters for window protection 90 54. Breakaway walls 91 % vii f