Water plans — Mayotte 2013 — BD Carthage

The main concept of hydrographic splitting is the hydrographic entity defined by Circular No 91-50. The hydrographic entity is a natural or developed watercourse, a natural or developed arm, an artificial waterway (canal, etc.), a waterplane or a coastal line. The nature of a hydrographic entity is not constant throughout the entity. For example, a natural watercourse may be built on a part. All these changes can be disclosed by distinguishing between sub-media on the entity. Hydrographic entities are broken down into two types: — linear hydrographic entities or rivers, — Surface hydrographic entities corresponding to water bodies and linear entities whose wide areas (over 50 metres) are represented by surface elements. A surface hydrographic entity may be crossed by a watercourse, which will be designated as the main watercourse. Each entity is identified by a unique generic code at national level. This 8-position alphanumeric code consists of dashes and characters. For example, a watercourse that passes through more than one area or sub-sector will have a generic code in the format of the following generic codes “V12-4000” or “R5-0420” (see below for the construction rule). In addition, a hydrographic entity has a so-called principal name. Rule for the construction of the generic code of the hydrographic entity: Each hydrographic entity shall be assigned a unique 3-digit number (5, 6 and 7th characters) for the medium and hydrographic area (s) to which it belongs: This is the number of the hydrographic entity. A hydrographic entity belonging to more than one area retains its entity number in all relevant areas. Two hydrographic entities from the same environment belonging to two different sub-media will have separate entity numbers. The first four characters of the generic code correspond to all the invariant codes of the hydrographic areas, the rest of the characters being replaced by dashes < — <. For example, the ‘Viveronne’ river has the following number: 050 and for middle code: 0. This river is located within a single hydrographic zone: P737. Its generic code is therefore: P7370500 The “La Dronne” river has the following entity number: 025 and for middle code: 0. This river crosses several hydrographic areas (even several sub-sectors): P746, P744, P742, P70, P734, P731, P730, P716, P715, P714, P711, P710, P702, P701, P700. Of these codes, only the two characters are invariant. Its generic code is therefore: P7-0250 Similarly, the Garonne has the following entity number: 000 and for middle code: 0. This course crosses several hydrographic sectors (all starting with ‘0’. Its generic code is: 0--00000 An area hydrographic entity is a hydrographic entity comprising water bodies and linear entities whose wide areas (over 50 metres) are represented by surface elements. A hydrographic entity is broken down into surface hydrographic elements. In some cases, an area hydrographic entity may be crossed by one or more rivers — in the case of water bodies. Nevertheless, it is accepted that only one hydrographic entity, known as the main watercourse of the water body. On the other hand, a hydrographic entity may be crossed/contained by a set of elementary sections.