Seasonal rainfall and poor natural drainage (the soil is developed on a crystalline substratum) led to the development of hydromorphic
soils classified as Gleysols according to the World Reference Base for Soil Resources (WRB) classification (WRB 2014).
Water stress is recurring environmental factors in Rio Grande do Sul since the southern zone of this state is characterized for presenting extensive areas of hydromorphic
soils, poorly permeable and with drainage problems (CUNHA and SILVEIRA, 1996).
The region has two soil types: (i) sandy soil, including the ferruginous tropical soil of the sandy valleys; and (ii) hydromorphic
soil located in the Niger River Valley.
The Central Depression of the State of RS has mainly Haplic Planosol soil, which is hydromorphic
due to a reduced infiltration capacity and high compaction rates (SARTORI et al.
The forests are on generally flat to undulating terrain that is predominantly underlain by deep unconsolidated Kalahari sand deposits with small patches of hydromorphic
black clay mainly in the vlei areas.
Yellow Acrisol, Fluvic Neosol, and Indiscriminate Hydromorphic
Soils are also present (Valente et al.
The soil in the experimental field is dark-yellow hydromorphic
Intra-zonal soils occupy a significant portion of the vineyard soil (>30%), the former being represented by regosols and erodisols on the more eroded slopes, and azonal, alluvial and/or hydromorphic
soils on the valley meadows.
The streams and rivers in the study area are formed mostly of hydromorphic
zones, in which surface runoff near the headwaters is intermittent.
structure combined with current precipitation controlling factors influence runoff and flash flood in the study area.
According to the French classification of soils (CPCS, 1967) the soils found in the study area are included into six classes: isohumic soils, vertisols, calcimagnesic soils, slightly developed soils, iron sesquioxides soils and hydromorphic
soils (Badraoui & al.
On the mainland side of the delta, however, the hydromorphic
soils were more efficiently drained as a consequence of the dredging and the reed bed communities were replaced by meadow species, whose establishment was even more facilitated by increased mowing of flood plains.