Part 2 PHASE-I STUDY: UNDERSTANDING OF PRESENT CONDITIONS AND FORMULATION OF FRAMEWORK FOR THE MASTER PLAN The Study on Integrated Basin Management Final Report Focused on Flood Control in Mejerda River Main report CHAPTER 3 FIELD SURVEYS 3.1 River Profile and Cross Section Survey The river profile and cross-section survey was conducted for the following sites and routes where flood control measures need to be planned: (1) Mainstream of the Mejerda River (from the Sidi Salem dam reservoir to the border between Tunisia and Algeria), (2) Major tributaries (Mellegue, Tessa, Bou Heutma, Kasseb, Beja Rivers and others), and (3) Prospective sites of flood control structures, such as retarding basins, bypass channels, ground-sills, bridges, dikes and revetments. Out of these survey areas, the item (1) survey, the mainstream of the Mejerda River and the item (2) survey, major tributaries, were conducted during the first and the second work in Tunisia, respectively. The item (3) survey was conducted during the third work in Tunisia. The technical specifications of the items (1) to (3) survey are as stated below. Item (1) Survey: Technical Specifications Survey area Mainstream of the Mejerda River (Upstream section from the Sidi Salem reservoir to the border with Algeria) Work quantity 1) River profile survey: about 180 km 2) Cross-sectional survey: 360 sections (about 500m interval along the river center, average width of about 330 m) Technical 1) Selection of survey points by use of the existing maps with scales of Specifications 1:25,000 – 50,000 2) River profile along the stream flow line (the deepest river channel) 3) Provision of one wooden/steel bar each on both sides of each river cross-section Survey outputs 1) Drawings of control survey networks and locations of profile and cross-sections (plan) 2) Drawings of river profile and river cross-sections 3) Survey records and reports 4) Survey drawings shall be of Auto CAD format. 5) Both paper drawings and digital files shall be submitted. Nippon Koei Co.,Ltd. 3-1 January 200９ The Study on Integrated Basin Management Final Report Focused on Flood Control in Mejerda River Main report Item (2) Survey: Technical Specifications Survey area Major tributaries situated between the Sidi Salem Reservoir and Jendouba: Mellegue, Tessa, Rarai, Bajer, Bou Heurtma, Kasseb and Beja Rivers Work quantity 1) River profile survey: about 140.6 km 2) Cross-sectional survey: 476 sections (about 250/500m intervals along the river center, average width of about 300 m) Technical 1) Selection of survey points by use of the existing maps with a scale of Specifications 1:25,000 2) River profile along the stream flow line (the deepest river channel) 3) Provision of one steel bar each on both sides of each river cross-section Survey outputs 1) Drawings of control survey networks and locations of profile and cross-sections (plan) 2) Drawings of river profile and river cross-sections 3) Survey records and reports 4) Survey drawings shall be of Auto Cad format. 5) Both paper drawings and digital files shall be submitted. Item (3) Survey: Technical Specifications Survey area Prospective sites of flood control structures in and along the mainstream of the Mejerda River (from the estuary to the border between Tunisia and Algeria) Work quantity 1) River profile survey: about 54.8 km 2) Cross-sectional survey: 72 sections (about 250m/100m intervals along the river/canal center, average width of about 200 m) Technical 1) Selection of survey points by use of the existing maps with scales of Specifications 1:25,000 – 50,000 2) River profile along the stream flow line (the deepest river/canal bed) 3) Provision of one steel bar each on both sides of each river cross-section Survey outputs 1) Drawings of control survey networks and locations of profile and cross-sections (plan) 2) Drawings of river profile and river cross-sections 3) Survey records and reports 4) Survey drawings shall be of Auto CAD format. 5) Both paper drawings and digital files shall be submitted. The survey results have been usefully reflected in the study work, particularly to the study on discharge capacities of river channels, flood inundation analysis and river improvement works for flood control measures. 3.2 Flood Inundation and Damage Survey The flood inundation and damage survey has been conducted to collect data and information in the field regarding flood inundation and damage due to previous major floods in the Mejerda River basin. The major flood events considered for this survey are those that occur in 1973, 2000, 2003, 2004 and 2005. Nippon Koei Co.,Ltd. 3-2 January 200９ The Study on Integrated Basin Management Final Report Focused on Flood Control in Mejerda River Main report The survey consists of the following two major activities: • Collection of data/information from related government agencies/offices, and • Questionnaire survey to residents/ shops/ farmers/ industries. The execution of both above activities was designed to obtain information on actual flood damage from two different sources. Regarding the data collection through questionnaire survey, prepared questionnaire forms were different for residents, shops, farmers and industries. Nevertheless, all forms basically contained questions about the following items: • General information of respondents, such as address and major income sources, • Inundation conditions including inundation date, water level, and duration, • Flood damage and inconvenience caused, • Experiences of inundation, such as behaviour after its occurrence. The questionnaire survey was conducted to 300 respondents in total at the cities/major towns which had experienced significant inundation damage due to past major floods. The survey results have been effectively referred to and employed in the Study, particularly the study work on flood inundation analysis, river improvement works for flood control measures and evaluation of project benefit for economic analysis of project. 3.3 Inventory Survey on Water Management Facilities 3.3.1 General The inventory survey on water management facilities was carried out to collect data and information, including physical characteristics, concerning water resources management and flood control facilities operated within the Mejerda River basin. The following items are included in the inventory survey: Classification Survey Item Pluviometric and hydrometric (A1) Rain gauging stations in the catchment measurement and monitoring (A2) Rain gauging stations in adjacent catchments (B) Stream gauging stations (C) Gauging stations used for flood early warning system (D) Water quality monitoring locations Hydraulic structures and obstructions (E) Dams (F) Crossing structures: bridge piers, pipelines, siphons (G) Weirs and other water level control structures Channel improvement works (H) Channel lining, flow diversion channels, and levees Erosion/ sediment control (I) Storm water detention for erosion control (hill dams) (J) Flow attenuation check dams for soil conservation Irrigation and drainage (K) Location of canal inlets/outlets and flood protection gates Groundwater resources (L1) Wells (L2) Shallow aquifers (L3) Deep aquifers Nippon Koei Co.,Ltd. 3-3 January 200９ The Study on Integrated Basin Management Final Report Focused on Flood Control in Mejerda River Main report Classification Survey Item Water use (M) Water intake facilities (N) Potable water facilities operated by SONEDE (O) Bulk water transfer facilities operated by SECADENORD (P) List of irrigated schemes (Q) Population of communes and sectors (R) Towns supplied with potable water from SONEDE Wastewater treatment (S) List of wastewater treatment schemes operated by ONAS Land use (T) Forestry land use (U) Agricultural land use (V) Land use by sub-catchment area Environment (W) List of wetlands and protected areas The information gathered during the inventory survey was used to understand the existing conditions in the basin, and to prepare master plan solutions aimed at improving flood control and early flood warning systems. 3.3.2 Description of Survey The inventory survey on water management facilities was carried out in two stages. (1) Stage 1 The first stage consisted of identifying the existing facilities located within the Mejerda River basin and collecting corresponding data related to its physical characteristics. Most of the data for said inventory survey were obtained from the MARH’s GEORE database. Locations of all inventory items and land use data have been geo-referenced to UTM coordinates. Population data and projections are as published by INS based on the most recent census taken in 2004. Boundaries for communes have been collected, but the sector boundaries within communes (the smallest unit of population) were not obtained as it required special permission from the Ministry of Defense. The approximate locations of levees were indicated by MARH on the topographic maps. However, heights and its existing conditions are unavailable. Limited information on heights of levees can be obtained from the cross sectional surveys that were carried out under the Study. (2) Stage 2 In the second stage, the inventory survey was conducted for collecting information pertaining to the operation and maintenance of the physical infrastructure that plays an important role in flood management. The collection of data was conducted in cooperation with DGBGTH. Finding a reliable source of information for some operation and maintenance data proved to be difficult. In the end, the survey was only able to obtain limited O&M data for several inventory Nippon Koei Co.,Ltd. 3-4 January 200９ The Study on Integrated Basin Management Final Report Focused on Flood Control in Mejerda River Main report items, namely, rain gauging stations, stream gauging stations, large dams, hydraulic control structures, levees, small hill dams and check dams. 3.3.3 Synopsis of Operation and Maintenance The survey result indicates that routine maintenance is almost non-existent and clearly suffers from a lack of funding. It also reveals that there is little or no preventive maintenance carried out. Key findings of the O&M survey are outlined in Table 3.3.1, and summarized below.