enquête (1) état (1) extraction de sable (1) sable (1) fleuve (1) politique (1) besoin (1) gestion (1) littérature (1) intérêts (1) ménage (1) analyse (1) extraction (1) environnement (1) activité minière (1) Gap (1) Afrique (1) Development (1) Area (1) Area (1) Threats (1) Strategy (1) South Africa (1) Series (1) Sand (1) Rivers (1) Nature and nurture (1) Mining engineering (1) Mines and mineral resources (1) Miners (1)