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In Bangladesh flood mitigation strategies have concentrated on embankments. However, due to a perceived lack of success with this strategy and high returns to irrigation development, the emphasis in water management switched towards small scale irrigation. Serious floods in 1987 and 1988 have renewed interest in flood mitigation. However, there is a lack of detailed evidence on the impacts of embankments. This study provides just such evidence. The study comprises a detailed post-evaluation of a major flood control, drainage and irrigation project, the Chandpur Irrigation Project. The results show that the project has been successful in reducing normal monsoon water levels, with consequent changes in cropping patterns to higher yielding varieties. However, a with-without comparison revealed that expected yields (allowing for risks of flooding and drainage problems) were less than predicted due to drainage problems within the project, whereas non-project expected yields are as predicted. Hence agricultural output has increased substantially, but output and its value are less than anticipated. Household incomes in the project are 25&37 higher (on average) than in control areas, but this is because larger landowners have gained from greater returns to agriculture (for example, from preferential access to irrigation), and diversifying into other occupations. Some households have gained by selling land and obtaining salaried jobs elsewhere or by becoming traders. By comparison small landowners may be slightly less prone to losses in flood years but have not moved into surplus. Landless labourers have similar incomes inside and outside the project; real wages are unchanged, and increased work has not compensated for population growth. Inside the project changes in landholding category have been fewer than outside. Open water fish populations have been reduced by the embankment, particularly affecting poor households. However, fish cultivation has expanded more than in flood prone areas, benefiting pond owners and enabling professional fishermen to maintain their incomes (at the cost of greater dependence on larger landowners). Improved methods of post-evaluation (which have implications for appraisal of new projects) are developed to incorporate flood risks and consequent yield reductions and non-agricultural damages, and to standardise economic valuation. Applying these methods revealed that the Chandpur Project has been, despite an uneven distribution of benefits, relatively successful (an economic rate of return of at least 5%). Although there are some project specific reasons for this success, this project has suffered many problems typical of embankment in Bangladesh. Hence embankments are potentially important for the future economic development of Bangladesh - by reducing damage and disruption and increasing agricultural output. The study concludes with recommendations for improved flood plain planning in Bangladesh, using detailed flood loss data and improved appraisal methods, to ensure that choice of flood mitigation strategies and investments are rational, and that all public investments take flood risks into account.

La STEP de Benslimane dont les effluents épurés sont réutilisés pour l’arrosage du Golf, comporte un système de lagunage aéré suivi de quatre réservoirs opérationnels. L’évolution des paramètres de pollution entre l’entrée des réservoirs et leur sortie, laisse voir des abattements moyens de 60% pour la DBO5, 40% pour la DCO, 48% pour les MES et 98% pour les coliformes.L’évolution des teneurs des différents paramètres de pollution sous le même régime d’opération et les mêmes conditions climatologiques est synchrone dans les quatre réservoirs témoignant des mêmes performances.Les résultats de la qualité de l’eau le long de la colonne d’eau du réservoir entre 40 cm et 350 cm montrent une colonne homogène où toutes les réactions se déroulent en aérobiose.Ces réservoirs permettent le stockage et la quasi purification microbiologique des effluents. Ils constituent une solution pour les pays arides et semi-arides pour l’épuration et le développement agricole. / Benslimane STEP is an aerated lagoons system followed by four operational tanks. The evolution of pollution parameters between input and output of the reservoirs, shows a removal of 60% for BOD5, 40% for COD, 48% for TSS and 98% for coliforms. Changes in concentrations of various pollution parameters under the same operating system and the same weather conditions is synchronous in the four reservoirs showing the same performance. The results of water quality along the reservoir's water column between 40 cm and 350 cm show an homogeneous column where all the reactions take place under aerobic conditions. These tanks can store and almost achieve a total microbiological purification of effluents. They are a solution to the arid and semi-arid areas for finishing of waste water and irrigation development.