Hers-Vif

The Hers-Vif (, "Live Hers", as opposed to the slower flowing Hers-Mort, "Dead Hers"), also named Grand Hers or simply Hers, is a 135 km long river in southern France, right tributary of the Ariège.

The Hers-Vif rises at an elevation of about 1500 m near the Chioula Pass of the Pyrenees, approximately 6 km north of Ax-les-Thermes. It is the major tributary of the Ariège into whose right bank it flows 2 km upstream from Cintegabelle in the Haute-Garonne.

It flows some 30 km through the Pyrenees, descending 1100 m to the village of Peyrat, where it reaches a piedmont plain. Its valley widens as it traverses the plain, reaching the medieval city of Mirepoix, which marks the start of its lower valley.

Several rivers flow into it:
 * From the Pyrenees: the Lasset; the Fontaine de Fontestorbes; the Touyre
 * From the piedmont plain and hills: the Blau and the Douctouyre;
 * From the hills of Lauragais and Razès: the Ambronne and the Vixiège.

Departments and towns along its course are:
 * Ariège: Prades, Bélesta, La Bastide-sur-l'Hers, Mirepoix, Mazères
 * Aude: Comus, Chalabre
 * Haute-Garonne: Calmont

Floods
The Hers is probably known as vif (intense or rapid in this context) because of its sometimes spectacular floods – that of 16 June 1289 having entirely destroyed Mirepoix. More recently, there have been:
 * 23 June 1875: estimated flow rate of 1500 m3/s at Mazères;
 * 6 February 1919: estimated flow rate of 600 to 800 m3/s at Mazères;
 * 19 May 1977: estimated flow rate of 1070 m3/s at Mazères;
 * 16 January 1981: estimated flow rate of 1100 m3/s at Mazères;
 * 11 June 2000: estimated flow rate of 500 m3/s at Mazères;
 * 24 January 2004: estimated flow rate of 500 m3/s at Mazères.