Gully distribution and development in Moldavia, Romania

In a study area in Romania covering about 25,000 km 2 over 9000 gullies were mapped and 12 were surveyed in detail. The distribution of gullies indicates that the highest gully density reflects hillslope orientation, inclination and length, and a sandy lithology. The surface deposits of gullies studied vary from silty-clays in the northern half of the territory, to silts in the middle to southern area and sands in the southern end of the region. Factorial analysis of geometrical and granulometrical variables showed the role of the M parameter as a discriminating value of gully cross section shape. The rate of gully head cutting is over 1.5 m/year for gullies cut in sandy deposits and under 1 m/year for the gullies cut in marls and clays. A model of gully development is proposed which shows an accelerated rate of gully development immediately downstream after their initiation and a reduced and even cessation of advance on attaining an equilibrium length.