Iraq - Technical report on the Wadi Tharthar Flood Control Project

No. Loan 85a RESTRICTED This report is restricted to use within the Bank. INTERNATIONAL BANK FOR RECONSTRUCTION AND DEVELOPMENT TECHNICAL REPORT ON THE WADI THARTHAR FLOOD CONTROL PROJECT IN IRAQ June 7, 1950 Loan Department  IRAQ TADI THA1IITHIR FLOOD CONTROL PROJECT 1. Purpose and Scope of this Report. This report presents a summary analysis of a report prepared by the Bank's consuiltant, Glen E. Edgerton, who visited Iraq with the Bank Miission in June and July, 1949. It includes also the recomrmendations of the Engineering Staff concerning this project. The Bank's consultant studied the draft of the report of the Irrigation Development Commission and had numerous conferences and discns- sions with its principal engineers as well as wvi-th engineers and others< outside the Government service. He made field inspections of the sites of the proposed lWadi Tharthar development. In addition, he conferred in Cairo with experts of the British lMiddle East Office and in London wi.th the conaulting engineers for the Iraq Government. Hle concluded that the proposed project for protection of Baghdad and other critical points on the Tigris against floods is economically justified. 2. Report of the Irrigation Development Commission. The Irrigation Development Comtnission was the agency employed by the Mlinistry of Public Works to prepare plans for the development of the water resources of Iraq. It consisted of a group of engineers headed by Ir, F. F. Haigh, a British engineer of extensive experience on cormparable work in India. The Commission spent about two and a half years investi- gating the possibilities of r iver regulation, storage and distribution, drainage and irrigation that appeared to warrant careful stuidy. Both field and office work have been carried on tGo the extuent deemed necessary for the preliminary or general designs and estimates of cost required to support the conclusions of the Commission in respect to the projects worthy of adoption and the order in which the more urgent projects should be undertaken. Detailed designs and specifications of the projeqt structllre re- main to be worked out in most cases, and some modification of the esti.mates may be expected when that work is completed. The preparation of the final designs anid specifications and the supervision of the awvard of contract and the work of the contractors on the major items of the work wrill be, under the present practice of the Government of Iraq, the responsibility of its consulting engineers, Mlessrs. Coode, Vaughan-Lee, Frarnk and Gi.',v[ther of London. This consulting firm is experienced and thoroughly reliable in every respect. The Irrigation Development Commission has now been dissolved.  2- 3. Tigris River Floods. The Tigris River which has its source in the mountains of IEastern Thrkey, has a length of about 770 miles in Iraq. It has an average slope of about 2.6 feet per mile in its upper reaches and 2 to h! inches per mile in the alluvial valley which begins about 85 miles above Baghdad. The mountainous section of the watershed. lies to the east of the main stream. Four great tributaries enter the main stream from this side, the largest of which, the Diala, has its mouth below Baghdad. The mount,ains of the Tigrist headwvaters have heavy rainfall anid. snow cover and. rapid runoff, resulting in quiclc, high and destructive floods. In the delta, the river is ',nfined by levees at critical points, the most important of whicl, is the ci-w of Baghdad. Here, rmluch of the lanid within the city is below flood levels of the river. lhe channel between the levees is of inadequate capacity to pass the major floods and flooding of the city is prevented only by the costly and not entirely reliable expedi.ent of opening a breach in the levees above the city on the east bank and allowig.ng the flood waters to by-pass the city to the eastwarcl where they do groat damage to the crops of a large and fertile area. The part of the city on the east bank of the Tigris is protected from the escaping waters as well as from the river by a ring of levees. A brealk in this ring in times of high flood would cause great damilage. Gauging stations have been maintained for over 25 years, The longest recQrd is that of the station at Baghdad which extends from 1206. The maximum reoorded discharge is about 11lh,000 cubic meters per second (cumecs) just below the mouth of the Diala. TIlhe minimum flow at the same location was 160 cumecs. There are two flood periods annually, Novemnber to March and April to May. Floods occur every year that result in damage both to urban property and to rural improvements. It is obvious that cne of the most urgent needs of the country is for cQntrol of Tigris diJver floocls anid the Irrigation Development Comminsion has stated in its reports that the flood control pro-- ject is amply justified. L4. Description of the Project. The Wadi Tharthar Flood Control Project contains the flood control elements of the multi-purpose lWadi Tharthar Project whlich latter ls a compre- hensive plan providing in addition to flood protectioui, river stor'age and regulation. It utilizes the Wadi Tharthar Depression for the storage of flood waters diverted from the Tigris River. The plans will provide, however, in thlis stage of the multi- purpose project, for construiction of the dam to withs land a head of 10 meters which would be recquired for future irrigation plans. This provision entails oinly gomparatively small structura'l chan-ges in the flood contrQl dam and cani be accomplished at a cost much less tlhan if made later after the floQd control dam were cQnstructed.  - 3- The Wadi Tharthar is a semi-desert valley lying between the 'uphrates and Tigris Rivers, extending from sources west of VIWosul about 300 kilometers in a south-easterly direction to the Tharthar Depression, which is about 65 kilometers northwest of Baghdad. Water flows in the Wadi Tharthar for only a short period in the spring of the year. The depress-ion has no outlet and the meager flow of the WA,adi Tharthar disappears through evaporation and seepage, leaving the bed of the depression dry and coverecl with salt during the greater part of the year. It has a storage capacity of about 68 billion cubic meters, or approximately 55 million acre feet. A dam in the Tigris river w,ill divert the excess flood waters through a diversion channel to the lVadi Tharthar Depression where it can be disposed of by evaporation. The proposed operation of the project consists merely of the manipulation of the gates of the dam to release the water in the river at rates not in excess of the capacity of the downstream chaninels at critical points, the most important of which is Baghdad. The maximum flood which has been carried through the city of Baghdad without disaster amounted to B,000 cubic meters per second. The December, 1941 flood which is the maximum. within the period of record, had an estimated discharge above Baghdad of 12,500 cubic meters per second and floods in excess of this amount may be expected in the future. Therefore, the diversion of 6,000 cubic meters per second from the river above Baghdad was considered by the Commission as the proper protection to be provided. initially with enlargement during the second stage of the comprehensive plan to 8,000 cubic meters per second. In the opinion of the Bank's consultant the greater capacity of 8,000 cubic meters per second should be provided in the initial construction. The principal features of the flood control project are a dama across the Tigris River above Sammara wkrith the necessary levees and training works, undersluices in the head reach of the inlet channel to dispose of silt and the inlet channel with its regulator, together with the relocation of existing roads, railways and structures near Sarnara. (1) The Sammadra Dam wvill have a discharge capacity of 7,000 cubibc mete-rs per second. It will be a concrete structure about 12% meters high and 318 meters long with 40 operating gate openings each 6 meters in width and designed to withstand a head of 10 meters. The foundat".on of the darni will consist of a mass concrete floor, 2 meters thick, res-ting on hard clay. Borings have been made according to conventional prac'bice and adequLabe pro- visions have been made to as.;ure safe foundation conditions. It will be tied into the east bank of the river by an earth levee. The dam will not provide significant storage capacity and is designed for diverting exces$ flood waters via the inlet channel to the Wadi Tharthar Depression and f'or regulating the flow in the Tigris River below . The preliminary engineering design and estimating on this project 'hlas been done by the Irrigation Devel- opment Commission. A firma of consulting engineers, i,essrs. Goode, Vaughan-Lee, Franlc and Gwyther of London reviewed the design of the project. It is con- sidered that the preliminary design of the struct;ure has been developed satisfactorily and that under the engineering supervision of the British consulting engineers it will be executed competently.  (2) Undersluices in the head reach of the inlet channel will ha-ve a discharge capacity of 1000 cubic meters per second and will be provided for the purpose of disposing of silt. They will be located in a concrete structure 12- meters high and 118 meters long and consist of 15 gate openings each 6 meters in width. (3) The inlet bhannel is to be excavated to a capacity of 5(0 clurmecs only and its regulator will be designed for 750 curnecs to meet fuIture require- ments. The length of the channel will be 61 kilometers nmeasured from the dam. A channel of the large capacity (6000 cumecs) required for the flood waters which it is proposed to divert, would involve very large quantities of excavation and would be correspondingly expensive. To avoid the principal part of that expanse, the expedient is adopted of excavating only a rclat'ively small channel of 500 cumecs capacity, using the excavated material to con- struct a strong levee on its eastern ba,nk for a total length of 55 kilollmetbers. The flow in this channel, when it is less than, bank full, will be controlle& bry the regulator, a concrete structure 10L- meters high and 741h meters lorig with 10 gate openincs each 6 meters in width. FLow in excess Qt the capacity of the regulator will escape freely past it and will overflow so much of the desert land to the westward of the excavated channel as may be requiired. That area is mostly unoccupied wasteland and compensation will be maade for small holdings that may be damaged. The valuable land to the east of the channel will be protected by the levee. It is nece3sary to excavate a chanmel to the full width below kilometer 51 for all of the flood waters to pass through the divide between the valleys of the Tigris and the 'Vadi Tharthar. Consequently, the channel remains the most expensive part of the project, notwrithstandi.ng the saving obtained by the open fJloodway as compared with a confine channel through- out. (4) It will be necessary to move the Sammara railroad station and to reconstruct 22 kilometei- Qf railway track. Two tnew bridges will be con- st;ructed, one over the inlet channel and one over the spillway channel of the dam. A new road, 25 kilometers long, will be built. fRailroad res:i- dential buildings and oflices, workshops and stores will be reconstructed. 5. Estiimated Cost of the Project. The following estimate of the cost of the project is based upon that of the Comnnission, revised and increased bv the Bankts Consultant to conform to the changes in the project plan to prov-ide additional chanxnel capacity that is deemed advisuble, and including the estimated cost of the structural changes necessary in the damn to provide fo& a head of 10 meters.  Estimated Costs (Figures in parentheses are "diners": 1 pound 1 di.nar 2.8 dollars) I. HEADWORKS. Item Total Djn,ar Cost in Cost in Cost in Cost Dollars Pounds. Di 1 er s . Dam 1,104,000 - )480,00Q 6211,000 Undersluices 296,000 - 110,000 186,000 Inlet Regulator 326,000 - 120,000 206,000 River Banks 346,000 - - 3.6,0oo0 Rzelocations 557,000 - - 557,000 Diversion wrorks 301,000 - - 301,000 Totals 2,930,000 - 710,000 2,220,000 Overhead & Con tingencies 6oo,oo 0 TOTAL 3,530,000 II. ILET CHANNEL Excavation & Embanlment 3,885,ooo 4,650,00o 505,000 1,680,000 (1, 700,000) Additional Capacity 945,000 1,l10,000 - 545,000 (hkoo ,,ooo) Compensation for Flooding 80,000 80,000 Compensation for Reservoir Area 135,000 - 135,000 Totals 5,045,000 5,780,000 505,000 2,11ho,000 (2,100,000) Overhead & Contingencies l, 075,000 TOTAlL 6.,120,000 III. SU.; t :ARY Headworks 2,930,000 - 710,000 2,220,000 Inlet Channel 5,0o450oo 5,780,000 505,000 2,l440,000 ( 2,100,000) Overhead & Contingencies 1,675,000 1,120,000 285,000 990,000 ( 1X0 v000) Interest during Construction 60o,o0o 1,700,000 - (600,000) TQTAIS 10,250,000 8,600oooo 1,0,o,o000 5,650,ooo (3o100,o000)- . _  6- 6. Construction and Expenditure Schedules. At an economical rate of progress, the project should be completed in about five years. The equipment to be purchased from the Uni-t;ed States will be used for channel excavation and levee construction. In the c`hann-iel there are 38,500,000 cubic meters of material to be moved and for the dam and levee a total of 2,500,000 cubic meters. The delivery of the tractors and scrapers and of the other earth-moving equipment will be completed during the second year. The peak period of construction will be reached in the third and fourth years. The equipment to be obtained from the Sterling Area will lie u.sed for construction of the headworks and wrill be delivered by the encl of -"hp second year. Thereafter, the delivery of the construction mat,erials, cement and steel, and the gates will be completed in the third and fouiirth years. For all of the equipment to be obtained fromn both areas, adeqaate allowances have been made for expert services and for the training of local operators and supervisors. The followiing is an estimate of the funds required, by years: Year Dollars Pounds Sterliny Dinars 1 45o,ooo 150,000 1(00,000 2 3,900,000 200,000 l,lQ0O,Q00 3 I,950,000 1470,000 1,)430,000 4 500OO00 530 ,000 2,220,000 5 o.00,000 150,000 800,000 6,900,000 1,500,000 E,65o,ooo Interest during Construction 1,700,000 TOTAI, 8,6oo,ooo 7. Justification of the Project. Reliable statistics a-re meager in respect to flood damages which would be eliminated by the 'adi Tharthar Project. IHowever, from figures in the Commission's report on expenditures for flood control and from informatioil drawvn from other sources, estinLmates of savings Qr the advantages vwhich can be measured in money- may be prepared. The following summary is considered conservative:  -7- I. Average Annual Savings or Accruals to fTovernmental Agencies. 1. Reduction of normal levee maintenance, estimnated at about half of the average current expenditure rate ID 100,000 2. Reduction of Flood Operations, emergency measures for raising, repairing or protecting levees in flood times. 5)0,Q0 3. Normal taxes on increased value of lands in former flood areas. 50OOO 4. Reduction of Expenditures for the relief of flood victims 300,000 5. Reduotion in damages to Government property other than levees and flood protection works, 1tO,000 Lotal Annual Benefits, governmental ID 54o,ooo II. Average Annual Benefits to individuals. 6. Reduction in losses of crops 6o0o,oo 7. Reduction in damage to private property other than crops. 120,000 Total annual benefits, non-~goverrnmental ID 720,000 TOTAL ANNUAL DENMFITS ID 1,260,030 Comparison of the estiimiated benefits with the cost of ID 10,250,000, shows that the annual savings amount to over 12% of the initial investment. Indirect and intangible benefits to the economy of the counttry, such as the general improvement resulting from the increased security of the large sections of the population, the general business improvement to be expected from increased crop values, but distinct from these values, and improvement in health anld sanitation in the flooded areas., are imriportant corollaries of flood control and give furtther support to the justi.fi-cation of the project which seems to be well established by its tangible benefits alone. It would be difficult to devise a plan for making the project self- liquidating. To do so would require some means of collecting fromn the individual beneficiaries a large part of the financi.al benefit which accrlles to them fromn the construction and operation of the project. In flood con- trol projects of this kind, the numbers and d:ispersion of the beneficiaries are so great, and the obstacles to acceptable determinatiorn of their relative interests so formidable, that an equitable distribution of the cost appears to be impracticable.  -8- 8, Recommendations. Tt is recornaiended that the Wadi Tharthar flood control project on the Tigris River is a suitable project from the engineerxing and economlic justification points of view to qualify for Bank assistance. Tho projec-t would prov:i.de for a dam, near Sarnmara.des-igned to withstand a head of 10 meters and with discharge capacity of 7000 cubic meters per second, under- sluices of 1000 cu.mecs capacity for silt disposal, and an inlet channiel with capacity of 8000 Qumecs through the divide and a regul>tor of 750 cumecs capacity, together with the necessary levees and training and remedial works.  DAM 7000 CUMECS UNDERSLUICES 1000 CUMECS INLET REGULATOR 750 CUMECS \ SAMMARA 500 CUMECS ( 000 KILOMETER 51 FROM DAM KILOMETER 61 FROM DAM WADI THARTHAR N FLOOD CONTROL PROJECT DIAGRAMMATIC SKETCH NOT TO SCALE BAGH DAD \ DISTANCE FROM BAGHDAD TO DEPRESSION -65 KM