Relationship between drought and soil erosion based on the normalized differential water index(NDWI)and revised universal soil loss equation(RUSLE)model

The Langat River Basin in Malaysia is vulnerable to soil erosion risks because of its exposure to intensive land use activities and its topography,which primarily consists of steep slopes and mountainous areas.Furthermore,climate change frequently exposes this basin to drought,which negatively affects soil and water conservation.However,recent studies have rarely shown how soil reacts to drought,such as soil erosion.Therefore,the purpose of this study is to evaluate the relationship between drought and soil erosion in the Langat River Basin.We analyzed drought indices using Landsat 8 satellite images in November 2021,and created the normalized differential water index(NDWI)via Landsat 8 data to produce a drought map.We used the revised universal soil loss equation(RUSLE)model to predict soil erosion.We verified an association between the NDWI and soil erosion data using a correlation analysis.The results revealed that the southern and northern regions of the study area experienced drought events.We predicted an average annual soil erosion of approximately 58.11 t/(hm^(2)·a).Analysis of the association between the NDWI and soil erosion revealed a strong positive correlation,with a Pearson correlation coefficient of 0.86.We assumed that the slope length and steepness factor was the primary contributor to soil erosion in the study area.As a result,these findings can help authorities plan effective measures to reduce the impacts of drought and soil erosion in the future.

Relationships between land use types and urban heat island intensity in Hulu Langat district,Selangor,Malaysia

Background Urban heat island(UHI)is an urban climate phenomenon that primarily responds to urban conditions and land use change.The extent of hard surfaces significantly influences the thermal properties of the land.To address this issue,a novel approach quantifying the association between land use and UHI is developed.This study offers a new technique for effectively estimating the effect of land use on the UHI intensity using the combination of urban heat intensity index(UHII)and land contribution index(LCI)derived from Landsat 8 OLI images.The time-series thermal effect of land use on the UHI intensity can be determined according to the ratio in mean temperature between specific land use and the whole study site.The study was conducted in the Hulu Langat district,Malaysia during 2014-2021.Results The UHI intensity rose from 0.19 in 2014 to 0.70 in 2021.The negative value of LCI for vegetation areas and water bodies obtained its negative contribution to the urban heat island,while the positive value of LCI for bare areas and built-up areas showed its positive effect on the urban heat island.The LCI value for urban areas showed a significant increase in the 7 years such as 0.51,0.66,0.69,and 0.75 for periods 2014,2016,2018,and 2021,respectively.The change in LCI from 2014 to 2021 for the transformation of bare area and forest was recorded to be 0.23 and−0.02,respectively.Thus,the conversion of forests into urban areas had a negative effect on the increment of UHI intensity.Conclusions Overall,these findings are useful for policy-making agency in developing an effective policy for reducing high UHI intensity and planning long-term land use management.