Assessment of Prospects for Flood Hazard Mitigation in the La Paz River Watershed Area
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ASSESSMENT OF PROSPECTS FOR FLOOD HAZARD MITIGATION IN THE LA PAZ RIVER WATERSHED AREA PROJECT EXECUTED BY CARE BOLIVIA – USAID 2002 ASSESSMENT OF PROSPECTS FOR FLOOD HAZARD MITIGATION IN THE LA PAZ RIVER WATERSHED AREA TABLE OF CONTENTS ASSESSMENT OF PROSPECTS FOR FLOOD HAZARD MITIGATION IN THE LA PAZ RIVER WATERSHED AREA ............................................................................................................................... 1 ASSESSMENT OF PROSPECTS FOR FLOOD HAZARD MITIGATION IN THE LA PAZ RIVER WATERSHED AREA ............................................................................................................................... 2 TABLE OF CONTENTS........................................................................................................................... 2 EXECUTIVE SUMMARY ......................................................................................................................... 8 EXECUTIVE SUMMARY ......................................................................................................................... 8 1 BACKGROUND ............................................................................................................................ 14 1.1 GEOGRAPHY ........................................................................................................................... 15 1.1.1 The High plateau (Altiplano), ............................................................................................ 15 1.1.2 The Sub Andean Zone, .................................................................................................... 15 1.1.3 The Amazon Tropics,........................................................................................................ 15 1.2 POPULATION ........................................................................................................................... 15 1.3 CLIMATE ................................................................................................................................. 15 1.4 THE CLIMATIC EVENT OF FEBRUARY 19, 2002........................................................................... 16 1.4.1 Urban Area of the city of La Paz....................................................................................... 16 1.4.2 The rural area of the La Paz River Sub-Watershed, from Jupapina to Tahuapalca ........ 20 2 OBJECTIVES OF THE ASSESSMENT........................................................................................ 22 3 THE STUDY AREA ....................................................................................................................... 22 3.1 SELECTION OF MICRO-WATERSHEDS TO BE ANALYZED............................................................... 23 3.1.1 In the city of La Paz: ......................................................................................................... 23 3.1.2 In the Río Abajo area:....................................................................................................... 23 4 REFERENTIAL FRAMEWORK OF THE STUDY AREA GEOLOGY .......................................... 24 4.1 STRATIGRAPHIC SYNTHESIS OF THE REGION ............................................................................. 24 4.2 SICA SICA FORMATION (SILURIC - DEVONIC)............................................................................. 24 4.3 ARANJUEZ FORMATION............................................................................................................ 25 4.4 VILA VILA FORMATION ............................................................................................................. 25 4.5 CATAVI FORMATION................................................................................................................. 25 4.6 BELEN FORMATION.................................................................................................................. 25 4.7 LURIBAY FORMATION............................................................................................................... 25 4.8 LA PAZ FORMATION................................................................................................................. 26 5 NATURAL HAZARDS IDENTIFIED IN THE LA PAZ RIVER WATERSHED AND ITS SURROUNDINGS.................................................................................................................................. 27 5.1 NATURAL RESTRICTIONS AND HAZARDS IN THE LA PAZ WATERSHED AREA .................................. 27 5.1.1 Natural restrictions............................................................................................................27 5.1.2 Natural hazards ................................................................................................................ 30 6 WORK METHODOLOGY, INFORMATION GATHERING AND CONSULTED DOCUMENTS... 34 6.1 USED DOCUMENTS .................................................................................................................. 35 6.1.1 Maps ................................................................................................................................. 35 6.1.2 Air photographs and satellite images ............................................................................... 35 6.1.3 Consulted bibliography ..................................................................................................... 35 6.2 ANALYSES............................................................................................................................... 36 6.3 MAPPING ................................................................................................................................ 36 7 SPECIFIC HAZARDS PER ZONE ................................................................................................ 37 8.1 CITY OF LA PAZ....................................................................................................................... 37 7.1.1 Description of Elected Watercourses in the City of La Paz.............................................. 37 7.1.2 Summary of results of mapping of floods, underground flooding, landslides and falling walls registered by the Emergency Relief Service of the Municipality of La Paz.......................... 48 2 7.1.3 Conclusions and recommendations regarding risk analysis in the micro-catchments of the city of La Paz. ................................................................................................................................ 51 7.2 RÍO ABAJO.............................................................................................................................. 52 7.2.1 Description of the micro-watersheds ................................................................................ 52 7.2.2 Conclusions and recommendations on the hazard analysis in the Río Abajo micro- watershed area .............................................................................................................................. 62 8 AREAS THAT ARE MOST VULNERABLE TO FLOODS AND INHERENT HAZARDS............. 63 8.1 MOST VULNERABLE AREAS IN THE CITY OF LA PAZ: ................................................................... 63 8.2 MOST VULNERABLE AREAS IN THE RÍO ABAJO AND ACHOCALLA REGION: .................................... 67 8.2.1 Achocalla River Micro-watershed..................................................................................... 67 8.2.2 Choqueyapu River Sub-watershed - La Paz .................................................................... 68 9 AGRO-FORESTRY COMPONENT............................................................................................... 70 9.1 OBJECTIVES............................................................................................................................ 70 9.2 METHODOLOGY....................................................................................................................... 70 9.3 DESCRIPTION OF THE STUDY AREA ........................................................................................... 70 9.4 VEGETATION: .......................................................................................................................... 72 9.4.1 Vegetation in the urban area ............................................................................................ 76 9.4.2 Achocalla Valley: .............................................................................................................. 79 9.4.3 Río Abajo .......................................................................................................................... 81 9.5 CONCLUSIONS......................................................................................................................... 90 9.6 RECOMMENDATIONS................................................................................................................ 90 10 SOCIO-CULTURAL COMPONENT.............................................................................................. 92 10.1 INTRODUCTION TO THE SOCIO-CULTURAL COMPONENT ............................................................. 92 10.2 OBJECTIVES OF THE SOCIO-CULTURAL COMPONENT ................................................................. 93 10.3 CONCEPTUAL FRAMEWORK...................................................................................................... 93 10.4 RESEARCH METHODOLOGY ..................................................................................................... 94 10.5 RESULTS, FINDINGS AND CONCLUSIONS..................................................................................