Impact of temporal rainfall patterns on flash floods in Hue City, Vietnam

Characterization of lower Phong river dissolved organic matters and formations of unknown chlorine dioxide and chlorine disinfection by-products by Orbitrap mass spectrometry

The main objective of this research was to evaluate land use and land cover (LULC) change in Battambang province of Cambodia over the last two decades. The LULC maps for 1998, 2003, 2008, 2013 and 2018 were produced from Landsat satellite imagery using the supervised classification technique with the maximum likelihood algorithm. Each map consisted of seven LULC classes: built-up area, water feature, grassland, shrubland, agricultural land, barren land and forest cover. The overall accuracies of the LULC maps were 93%, 82%, 94%, 93% and 83% for 1998, 2003, 2008, 2013 and 2018, respectively. The LULC change results showed a significant increase in agricultural land, and a large decrease in forest cover. Most of the changes in both LULC types occurred during 2003–2008. Overall, agricultural land, shrubland, water features, built-up areas and barren land increased by 287,600 hectares, 58,600 hectares, 8300 hectares, 4600 hectares and 1300 hectares, respectively, while forest cover and grassland decreased by 284,500 hectares and 76,000 hectares respectively. The rate of LULC changes in the upland areas were higher than those in the lowland areas of the province. The main drivers of LULC change identified over the period of study were policy, legal framework and projects to improve economy, population growth, infrastructure development, economic growth, rising land prices, and climate and environmental change. Landmine clearance projects and land concessions resulted in a transition from forest cover and shrubland to agricultural land. Population and economic growth not only resulted in an increase of built-up area, but also led to increasing demand for agricultural land and rising land prices, which triggered the changes of other LULC types. This research provides a long-term and detailed analysis of LULC change together with its drivers, which is useful for decision-makers to make and implement better policies for sustainable land management.

Evaluation of Land Use and Land Cover Change and Its Drivers in Battambang Province, Cambodia from 1998 to 2018

Soil erosion causes land degradation which negatively impacts not only natural resources but also livelihoods of people due to low agricultural productivity. Cambodia is prone to soil erosion due to poor agricultural practices. In this research we use Battambang province as a case study to quantify impact of land use and land cover change (LULC) on soil erosion. This study assessed the impact from LULC changes to soil erosion. LULC change maps were analyzed based on Landsat satellite imagery of 1998, 2008, and 2018, computed in QGIS 6.2.9, while the soil erosion loss was estimated by the integration of remote sensing, GIS tools, and Revised Universal Soil Loss Equation (RUSLE) model. The results showed that the area of agricultural land of Battambang province significantly increased from 44.50% in 1998 to 61.11% in 2008 and 68.40% in 2018. The forest cover significantly decreased from 29.82% in 1998 to 6.18% in 2018. Various soil erosion factors were estimated using LULC and slope. Based on that, the mean soil loss was 2.92 t/ha.yr in 1998, 4.20 t/ha.yr in 2008, and 4.98 t/ha.yr in 2018. Whereas the total annual soil loss was 3.49 million tons in 1998, 5.03 million tons in 2008, and 5.93 million tons in 2018. The annual soil loss at the agricultural land dramatically increased from 190,9347.9 tons (54%) in 1998 to 3,543,659 tons (70.43%) in 2008 and to 4,267,439 tons (71.91%) in 2018 due to agricultural land expansion and agricultural practices. These losses were directly correlated with LULC, especially agricultural land expansion and forest cover decline. Our results highlight the need to develop appropriate land use and crop management practices to decrease land degradation and soil erosion. These data are useful to bring about public awareness of land degradation and alert local citizens, researchers, policy makers, and actors towards land rehabilitation to bring the area of land back to a state which is safe for increasing biodiversity and agricultural productivity. Measures to reduce or prevent soil erosion and the use of conservation agriculture practices, along with water and soil conservation, management, agroforestry practices, vegetation cover restoration, the creation of slope terraces, and the use of direct sowing mulch-based cropping systems should be considered.

/pdf/assessment-of-land-use-and-land-cover-changes-on-soil-30cm3gyb.pdf

Assessment of Land Use and Land Cover Changes on Soil Erosion Using Remote Sensing, GIS and RUSLE Model: A Case Study of Battambang Province, Cambodia

Impact of deforestation on soil erosion in the highland areas of western Ethiopia using geospatial techniques: a case study of the Upper Anger watershed

Agricultural expansion and urban development without proper soil erosion control measures have become major environmental problems in Cambodia. Due to a high population growth rate and increased economic activities, land use and land cover (LULC) changes will cause environmental disturbances, particularly soil erosion. This research aimed to estimate total amounts of soil loss using the Revised Universal Soil Loss Equation (RUSLE) model within a Geographic Information System (GIS) environment. LULC maps of Japan International Cooperation Agency (JICA) 2002 and Mekong River Commission (MRC) 2015 were used to evaluate the impact of LULC on soil erosion loss in Stung Sangkae catchment. LULC dynamics for the study periods in Stung Sangkae catchment showed that the catchment experienced a rapid conversion of forests to paddy rice fields and other croplands. The results indicated that the average soil loss from the catchment was 3.1 and 7.6 t/ha/y for the 2002 and 2015 periods, respectively. The estimated total soil loss in the 2002 and 2015 periods was 1.9 million t/y and 4.5 million t/y, respectively. The soil erosion was accelerated by steep slopes combined with the high velocity and erosivity of stormwater runoff. The spatial distribution of soil loss showed that the highest value (14.3 to 62.9 t/ha/y) was recorded in the central, southwestern and upland parts of the catchment. It is recommended that priority should be given to erosion hot spot areas, and appropriate soil and water conservation practices should be adopted to restore degraded lands.

https://www.mdpi.com/2071-1050/13/16/9276/pdf

Land Use and Land Cover Changes and Its Impact on Soil Erosion in Stung Sangkae Catchment of Cambodia

Floodplain management and mapping is a new and applied method for the river engineering and is essential for prediction of flood hazards. The lower Phong Basin area regularly goes more or less under flooding every year in the monsoon season due to lack of flood protection and limited resources. Most of the flood protection works are carried out at the local level without preplanning and considering the problems at the river basin scale. Traditionally, individuals or communities have been trying to develop their own strategies for minimizing the effects of floods. However, due to limitation of resources and knowledge, many householders are unable to protect their properties or possessions from floods. A methodology was applied to integrate hydraulic simulation model, HEC-RAS and GIS analysis for delineation of flood extents and depths within a Nam Phong River in northeast of Thailand. It is necessary to simulate complicated hydraulic behaviour of the river in a more simple way for the purpose of managing and performing all river training works. In this research, the steady flow was used to simulate flood along 148 km end of Nam Phong River starting at upstream from Ubolratana Dam to Chi River in Northeast of Thailand. Floodplain mappings were derived using integrating of HEC-RAS and GIS analysis. Delineation of flood extents and depths within the floodplain were conducted in different return periods. Critical flooding area along the river was distinguished based on the grid layer of flood depths. The results indicated that hydraulic simulation by integrating with GIS analysis could be effective for various kinds of floodplain management and mapping and give as different scenarios for river training works and flood mitigation planning.

Floodplain mapping using HEC-RAS and GIS in Nam Phong River Basin, Thailand.

Floods are regularly happening in the urbanizing Nam Phong watershed, the northeastern region of Thailand. The lower Phong Basin area regularly goes more or less under water every year in monsoon due to lack of flood protection and limited resources [4]. The damage of flood normally courses property losses, houses and land use change to the lowland in the flood prone area. The objectives of the study were, 1) Determine the flood frequency and flood zoning of the Nam Pong River at a return period of 5, 10, 25, 50, and 100 years, 2) Mapping the flood damage from the simulation varied with the different return periods. In this paper, the estimation of flood damage based on various return periods on Nam Pong watershed (2993.95 km) was carried out by 1D hydrodynamic simulation with HEC-RAS model which the runoff was simulated by the SWAT model for 10-year rainfall records (2000–2010), the Gumbel‘s method had been used to analyze the flood frequencies with various return periods and the water released from Ubolratana dam were also analyzed as scenarios for inputting to the HEC-RAS model. The simulation of inundated area was conducted using hydrodynamic program HEC-RAS.4.1 for the flood of 5, 10, 25, 50 and 100-year return periods. The simulation has revealed that the percent of flood damage is 20%, 23.2%, 27.8%, 34.3%, and 38.5% at return period 5, 10, 25, 50, and 100 years, respectively. The various flood damage mappings were prepared according to the simulation result using the software ArcView. The map showed that the flood damage with 50 and 100-year return periods had affected moderately to the agricultural and urban area. In the future, these two maps should be helpful in raising awareness of flood damages and in assigning priority for emergency preparedness in the affected area.

Nareth Nut

Papers

Land Use and Land Cover Changes and Its Impact on Soil Erosion in Stung Sangkae Catchment of Cambodia

Evaluation of Land Use and Land Cover Change and Its Drivers in Battambang Province, Cambodia from 1998 to 2018

Assessment of Land Use and Land Cover Changes on Soil Erosion Using Remote Sensing, GIS and RUSLE Model: A Case Study of Battambang Province, Cambodia

Floodplain mapping using HEC-RAS and GIS in Nam Phong River Basin, Thailand.

Estimation of flood damages on namphong river by hec-ras