Fonctionnement et entretien des fossés d'assainissement dans le marais Charentais

Drainage ditch operation and maintenance in the Charente-Maritime marshes

Ingénieur du Génie Rural, des Eaux et des Forêts, à la Direction départementale de l'Agriculture de la Charente-Maritime.

Résumé

The formation and structure of the Charente-Maritime marshes are described and the leading features of their drainage networks stated. This is followed by a brief analysis of the governing ditch design principles and network operating characteristics, especially those having a direct bearing on maintenance requirements, i.e. the following: (i) The importance of the tertiary ditch network as regards the regulating capacity of the network, in which the flow is tidal; (ii) The low flow velocities, which are conductive to weed growth; (iii) Water level variations due to the intermittent flow. The main ditch maintenance methods are then described, i.e. the following: 1. Chemical weed destruction. The most important weeds todestroy are listed, also produets in current use and the most frequent forms of treatment, i.e. treatment of the plants in situ above or under water, and sterilization. 2. Mechanical weeding. The main types of mechanical ditch-clearing equipment are briefly reviewed, including mechanical shovels, suction dredgers, helical clearers, etc. The author dwells at length on special equipment of the helical type made in Germany and prototypes of similar equipment produced in the Charente-Maritime region. The report closes with a few words on maintenance methods for wideditches, tidal ditches and small ditches, the common feature of which is that they aIl involve the use of chemical weed-killing techniques and mechanical maintenance equipment.