Mohd Ahmed

Risk assessment of soil erosion in semi-arid mountainous watershed in Saudi Arabia by RUSLE model coupled with remote sensing and GIS

Soil erosion is the most important factor in land degradation and influences desertification in semi-arid areas. A comprehensive methodology that integrates revised universal soil loss equation (RUSLE) model and GIS was adopted to determine the soil erosion risk (SER) in semi-arid Aseer region, Saudi Arabia. Geoenvironmental factors viz. rainfall (R), soil erodibility (K), slope (LS), cover management and practice factors were computed to determine their effects on average annual soil loss. The high potential soil erosion, resulting from high denuded slope, devoid of vegetation cover and high intensity rainfall, is located towards the north western part of the study area. The analysis is investigated that the SER over the vegetation cover including dense vegetation, sparse vegetation and bushes increases with the higher altitude and higher slope angle. The erosion maps generated with RUSLE integrated with GIS can serve as effective inputs in deriving strategies for land planning/management in the environmentally sensitive mountainous areas.

Spatial variability of soil erodibility and its correlation with soil properties in semi-arid mountainous watershed, Saudi Arabia

Soil erodibility values are best estimated from long-term direct measurements on runoff-plots; however, in lack of field tests, these values can be estimated using relationships based on physico-chemical soil properties. The study objective was to assess the erodibility and its correlation with soil properties. The average erodibility value was estimated 0.043 t ha h ha−1 MJ−1 mm−1. The areas with heavy textured soil and low organic matter content had the lowest values of erodibility. The erodibility decreases as the sand content increases, whereas silt showed a positive correlation. The erodibility factors and its relation to soil properties were evaluated using multiple regression analysis. Results revealed that sand and organic matter content of soil combinedly explained 78% of variation. Altitudinal increases also seem to affect the soil texture. This study has demonstrated that soil properties and erodibility values can be used as assistance for soil conservation practices and modelling of landscape processes.

Evaluating the co-relationship between concrete flexural tensile strength and compressive strength

The relationship of flexural tensile strength and compressive strength for different range of concrete strength proposed by various authors and country standards indicate diverse and wide variations in recommendations to predict the concrete flexural tensile strength. This paper presents the experimental study to predict flexural tensile strength and compressive strength improved empirical relations using statistical procedures for wide range of concrete strength (35 to 100 MPa) and for different member depth of concrete (80 to 250 mm). It is concluded from study that the flexural tensile strength and compressive strength proportionality equations should be derived in power model for more precision, and the size of the member should also be included in the proportionality equations in addition to compressive strength.