DDT 70 — Isocotes of PPRI n° 20120003 Saône_Medium

The isocotes of the PPRI are the altimeter values (Z in the NGF 69 marker) of the flood heights calculated for the reference flood. Subject to rules for constructions and recommendations to be observed, laid down in the regulation of the PPRI, isocotes allow the calculation of the altimetry of the highest waters to be observed for the establishment of an authorised construction. This height is calculated as follows: Z = (a * z2 + b * Z1)/(a+b) with Z1 = nearest isocot of highest value, Z2 = nearest isocot of lowest value, a = distance between point Z and Z1 measured perpendicular to the route of the isocot, b = distance between point Z and isocot Z2, measured perpendicularly to the route of the isocot. An explicit schema this formula is generally found in the appendix to the PPRI submission note.