Meteorological drought analysis using copula theory and drought indicators under climate change scenarios (RCP)

AbstractThe study was carried out to assess meteorological drought on the basis of the standardized precipitation index (SPI) and standardized precipitation evapotranspiration index (SPEI) evaluated in future climate scenarios. Yazd province, located in an arid region in the centre of Iran, was chosen for analysis. The study area has just one synoptic station with a long‐term record (56 years). The impact of climate change on future drought was examined by using the CanESM2 of the CMIP5 model under three scenarios, that is, representative concentration pathways RCP2.6, RCP4.5 and RCP8.5. Given that a drought is defined by several dependent variables, the evaluation of this phenomenon should be based on a multivariate analysis. For this purpose, two main characteristics of drought (severity and duration) were extracted by run theory in a past (1961–2016) and future (2017–2100) period based on the SPI and SPEI, and studied using copula theory. Three functions, that is, Frank, Gaussian and Gumbel copula, were selected to fit with drought severity and duration. The results of the bivariate analysis using copula showed that, according to both indicators, the study area will experience droughts with greater severity and duration in future as compared with the historical period, and the drought represented by the SPEI is more severe than that associated with the SPI. Also, drought simulated using the RCP8.5 scenario was more severe than when using the other two scenarios. Finally, droughts with a longer return period will become more frequent in future

The effect of traffic on forest road surface erosion (Case study: Kohmian forest- Azadshahr)

Sediment production is one of the most consequences of forest road construction. Soil erosion and its consequences is one of the major environmental problems. Erosion of unpaved roads occurs when soil particles are loosened and carried from the road into the drainage system and rivers. So estimating the amount of sediment delivered from forest roads is an important issue. In this study the effect of traffic on sediment and runoff yield was assessed using a rainfall simulator. Setting up the simulator with 1×1 plot, rainfall simulation was conducted during a 30 minute period and the resulted rain fall was collected in the outlet of plot. The results showed significant difference between run off and sediment yield of two traffic classes. Sediment delivered from the road surface with high and low traffic classes were 166.41 and 36.75 g/m2, respectively whereas run off rates for roads with high and low traffic classes were 49.1 and 22.1 lit/ m2. Significant effect of traffic on run off and sediment yield shows the importance of considering standard materials in road construction and maintenance. Considering the impact of traffic on amount of sediment and runoff, is elemental in planning, construction, and maintenance of forest roads

Future Rainfall Erosivity over Iran Based on CMIP5 Climate Models

Soil erosion affects agricultural production, and industrial and socioeconomic development. Changes in rainfall intensity lead to changes in rainfall erosivity (R-factor) energy and consequently changes soil erosion rate. Prediction of soil erosion is therefore important for soil and water conservation. The purpose of this study is to investigate the effect of changes in climatic parameters (precipitation) on soil erosion rates in the near future (2046–2065) and far future (2081–2100). For this purpose, the CMIP5 series models under two scenarios RCP2.6 and RCP8.5 were used to predict precipitation and the R-factor using the Revised Universal Soil Loss Equation (RUSLE) model. Rainfall data from synoptic stations for 30 years were used to estimate the R- factor in the RUSLE model. Results showed that Iran’s climate in the future would face increasing rainfall, specially in west and decreasing rainfall in the central and northern parts. Therefore, there is an increased possibility of more frequent occurrences of heavy and torrential rains. Results also showed that the transformation of annual rainfall was not related to the spatial change of erosion. In the central and southern parts, the intensity of rainfall would increase. Therefore, erosion would be more in the south and central areas