Montero town on the Pirai river

Technical Assistance for the program of Montero protection against floods, on the Pirai stream



Name of Client

SEARPI (Servicio de Encauzamiento de Aguas y Regularización del Rio Pirai)

Financing sources



CNR – France (member)


09/1994 - 09/2000

Project Description

Coordination of works for the protection of urban areas, infrastructures, rural area recovery, assistance and reorganization of SEARPI (6 years planned).
The Program includes the experimental study, final design and implementation of waterworks for the harnessing of Río Piraí between Bridge La Bélgica and Bridge Eisenhower (30 km), the purpose being:
- to protect Montero (56 000 inhabitants) against flooding and ensure better living conditions;
- to protect social, energetic and economic infrastructures and ensure the continuity of the regional and national transit of the Santa Cruz-Yapacani-Cochabamba Road and Beni Railways;
- to reclaim and upgrade the quality of agricultural lands (15 000 ha) in order to obtain better results in agricultural yields and cattle raising;
- to initialize a development boost in the Program area;
- to strengthen SEARPI organization.
Main activities have included:
- a study of the river morphology with the application of empirical formulas and direct observations for the focussing of the generalized and punctual erosion phenomenons.;
- an hydrological study to complete the historical data series of the previous Plan (1989-91) and update (with the last years historical data) in order to determine drainage works in the area;
- an hydraulic study to determine the flood heights depending on the land morphology and river-bed capacity;
- an hydraulic study to determine the water heights in case of a controlled flow;
- creation of a pilot-farm for experimentation and selection of herbaceous varieties and shrubs for the protection of slopes and controlled flooding areas;
- monitoring and non-stop archiving of Piraí stream physical and dynamic parameters variations;
- Final Design and preparation of Bid documentation for the implementation of Piraí stream harnessing waterworks and protection of Montero;
- implementation management and supervision;
- training of national staff for the management and maintenance of waterworks.
Main waterworks studied, designed and in progress are:
- a 60-km damming against the floods, along the right bank. The dammings are made of local construction material (sands) and a height varying from 1 m to 5 m;
- Realization of 20 protection works for the banks which control the flow.
Permeable works realized with steel bay on piles fixed in the stream bed;
- Stream bed correction through building pit.
The Piraí stream has important slopes and different deliveries varying within very short times from 50-100 m³/s to 2 000-3 000 m³/s (very sharp-shaped hydrograms). A Montero, the river-bed is running into the alluvial cone, thus being subject to a change in its course as present river-bed is gradually filling up. In occasion of the maximum flood discharge (2 000-3 000 m³/s), erosion can dig the river-bed on a depth down to 8 m or more. For this purpose, the Program has considered the use of 11-m pre-cast reinforced concrete posts driven into the river-bed on a 9-m depth. For the manufacturing of such pre-cast posts (8 000 posts required), a special factory has been created. The Program has also considered the installation of a soil laboratory for soil tests and analyses required at design stage as well as during construction works.

Services Description

Montero Flooding Control Program includes a 6-year TA in support of SEARPI - Servicio de Encauzamiento y Acondicionamiento del Río Piraí. Final design.