Heavy metals from heavy land use? Spatio-temporal patterns of urban runoff metal loads

Although a detailed analysis of land use and land cover (LULC) change is essential in providing a greater understanding of increased human-environment interactions across the coastal region of Bangladesh, substantial challenges still exist for accurately classifying coastal LULC. This is due to the existence of high-level landscape heterogeneity and unavailability of good quality remotely sensed data. This study, the first of a kind, implemented a unique methodological approach to this challenge. Using freely available Landsat imagery, eXtreme Gradient Boosting (XGBoost)-based informative feature selection and Random Forest classification is used to elucidate spatio-temporal patterns of LULC across coastal areas over a 28-year period (1990-2017). We show that the XGBoost feature selection approach effectively addresses the issue of high landscape heterogeneity and spectral complexities in the image data, successfully augmenting the RF model performance (providing a mean user’s accuracy > 0.82). Multi-temporal LULC maps reveal that Bangladesh’s coastal areas experienced a net increase in agricultural land (5.44%), built-up (4.91%) and river (4.52%) areas over the past 28 years. While vegetation cover experienced a net decrease (8.26%), an increasing vegetation trend was observed in the years since 2000, primarily due to the Bangladesh government’s afforestation initiatives across the southern coastal belts. These findings provide a comprehensive picture of coastal LULC patterns, which will be useful for policy makers and resource managers to incorporate into coastal land use and environmental management practices. This work also provides useful methodological insights for future research to effectively address the spatial and spectral complexities of remotely sensed data used in classifying the LULC of a heterogeneous landscape.

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Spatio-temporal patterns of the effects of precipitation variability and land use/cover changes on long-term changes in sediment yield in the Loess Plateau, China

10.5194/hess-2016-654 ◽

2017 ◽

Author(s):

Guangyao Gao ◽

Bojie Fu ◽

Murugesu Sivapalan

Keyword(s):

Land Use ◽

Surface Area ◽

Loess Plateau ◽

Sediment Yield ◽

Land Surface ◽

Sediment Load ◽

Temporal Patterns ◽

Precipitation Variability ◽

Spatio Temporal ◽

Annual Sediment

Abstract. Within China's Loess Plateau there have been concerted revegetation efforts and engineering measures over the last 50 years aimed at reducing soil erosion and land degradation. As a result, annual streamflow, sediment yield and sediment concentration have all decreased considerably. Human induced land use/cover change (LUCC) was the dominant factor, contributing over 70 % of the sediment load reduction, with reductions of annual precipitation contributing the remaining 30 %. In this study, we use data on 50-year time series (1961–2011), showing decreasing trends in the annual sediment loads of fifteen catchments, to generate spatio-temporal patterns in the effects of LUCC and precipitation variability on sediment yield. The space-time variability of sediment yield was expressed as a product of two factors representing: (i) effect of precipitation (spatially variable) and (ii) fraction of treated land surface area (temporally variable). Under minimal LUCC, annual sediment yield varied linearly with precipitation, with the precipitation-sediment load relationship showing coherent spatial patterns amongst the catchments. On the other hand, the effect of LUCC is expressed in terms of a sediment coefficient, i.e., ratio of annual sediment yield to annual precipitation, which is equivalent to the slope of the sediment yield-precipitation relationship. Sediment coefficients showed a steady decrease over the study period, following a linear decreasing function of the fraction of treated land surface area. In this way, the study has brought out the separate roles of precipitation variability and LUCC in controlling spatio-temporal patterns of sediment yield at catchment scale.

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Spatio‐Temporal Patterns of Land Use/Cover Changes Over the Past 20 Years in the Middle Reaches of the Tarim River, Xinjiang, China

Land Degradation and Development ◽

10.1002/ldr.2206 ◽

2013 ◽

Vol 26 (3) ◽

pp. 284-299 ◽

Cited By ~ 30

Author(s):

F. Zhang ◽

T. Tiyip ◽

Z. D. Feng ◽

H‐T. Kung ◽

V. C. Johnson ◽

...

Keyword(s):

Land Use ◽

Temporal Patterns ◽

Tarim River ◽

The Past ◽

The Tarim River ◽

Spatio Temporal

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Spatio-temporal patterns of the effects of precipitation variability and land use/cover changes on long-term changes in sediment yield in the Loess Plateau, China

Hydrology and Earth System Sciences ◽

10.5194/hess-21-4363-2017 ◽

2017 ◽

Vol 21 (9) ◽

pp. 4363-4378 ◽

Cited By ~ 20

Author(s):

Guangyao Gao ◽

Jianjun Zhang ◽

Yu Liu ◽

Zheng Ning ◽

Bojie Fu ◽

...

Keyword(s):

Land Use ◽

Surface Area ◽

Sediment Yield ◽

Land Surface ◽

Sediment Load ◽

Temporal Patterns ◽

Precipitation Variability ◽

Engineering Measures ◽

Spatio Temporal ◽

Annual Sediment

Abstract. Within China's Loess Plateau there have been concerted revegetation efforts and engineering measures since the 1950s aimed at reducing soil erosion and land degradation. As a result, annual streamflow, sediment yield, and sediment concentration have all decreased considerably. Human-induced land use/cover change (LUCC) was the dominant factor, contributing over 70 % of the sediment load reduction, whereas the contribution of precipitation was less than 30 %. In this study, we use 50-year time series data (1961–2011), showing decreasing trends in the annual sediment loads of 15 catchments, to generate spatio-temporal patterns in the effects of LUCC and precipitation variability on sediment yield. The space–time variability of sediment yield was expressed notionally as a product of two factors representing (i) the effect of precipitation and (ii) the fraction of treated land surface area. Under minimal LUCC, the square root of annual sediment yield varied linearly with precipitation, with the precipitation–sediment load relationship showing coherent spatial patterns amongst the catchments. As the LUCC increased and took effect, the changes in sediment yield pattern depended more on engineering measures and vegetation restoration campaign, and the within-year rainfall patterns (especially storm events) also played an important role. The effect of LUCC is expressed in terms of a sediment coefficient, i.e., the ratio of annual sediment yield to annual precipitation. Sediment coefficients showed a steady decrease over the study period, following a linear decreasing function of the fraction of treated land surface area. In this way, the study has brought out the separate roles of precipitation variability and LUCC in controlling spatio-temporal patterns of sediment yield at catchment scale.

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