akram lalozaei

Determining flood generation processes and incorporating them in hydrological studies can help make more reliable estimates. Focusing merely on mathematical computations in flood studies sometimes lead to paying less attention to the basic physical processes. Therefore, this research aims to present a process-based flood separation study for 20 hydrometric stations in the Gorganrood River Basin attributed as a flood prone area in the northern part of Iran. For this purpose, partial series of flood events at each station were extracted using the Peak-Over-Threshold (POT) approach selecting an optimal threshold value to determine flood events and considering the independence of the series values. Subsequent to characterizing flood events using some separation indicators including time of occurrence, rainfall duration, flood duration, air temperature, and antecedent soil moisture condition, different types of floods (i.e., floods caused by frontal precipitation, convective precipitation, snowmelt and rain on snow) were identified for each station. The results showed that floods caused by frontal precipitation and rain on snow have the highest and lowest frequencies in the basin, respectively. The research findings indicated that using POT approach and the indicators for classifying the different flood types can lead to a more accurate statistical analysis in flood studies and management.

The aim of this research is to study the impact the establishment of two types of windbreak, namely Tamarix aphylla and eucalyptus, on the soil characteristics in the Hamon plain, Sistan, Iran. In order, for each of the two species, a transect was set in 1.5 meter from plant canopy of the tree as treatment and a transect in distance of 50 meters from the trees as control. 30 points on each transect was selected and soil samples were taken at three depths (0-10, 10-30, 30-60 cm).The data of electro conductivity, acidity, the ratio of carbon to nitrogen, organic matter, potassium, magnesium, calcium, sodium, and texture of the soil, were analyzed using the SPSS software, paired t-test and analysis of variance in a randomized block design. Results showed that with the construction of the two windbreaks, electro conductivity, organic matter, calcium, potassium, sodium and carbon to nitrogen ratio had a significant (95%) increase compared to the control region. Furthermore, results showed that Tamarix aphylla in compared to eucalyptus, caused more increase in sodium, electro conductivity, and soil salinity, despite the fact that it causes an increase in organic C/N, carbon to nitrogen ratio, calcium, and potassium. In general, compared to eucalyptus, Tamarix aphylla windbreak has a better compatibility with the climate in the region Positive impact on soil properties, increasing soil organic matter levels and in the Long-term will help improve soil structure and soil also increases the necessary materials (nitrogen, phosphorus and potassium), the has more positive effects on the characteristics of the soil.