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Northwest A&F University (2017)

Effect of Landuse on Gully Headward Erosion Process in the Gully Region of the Loess Plateau

康宏亮;

Titre : Effect of Landuse on Gully Headward Erosion Process in the Gully Region of the Loess Plateau

Auteur : 康宏亮;

Grade : Master’s Theses 2017

Université : Northwest A&F University

Résumé partiel
Land use and vegetation cover have changed significantly after comprehensive implement of “grain for green” in the loess gully plateau region.Soil erosion environment improved essentially at some managed small-basins,which resulted in conservation of water and control of soil loss.However,Gully-head retreat caused by flood is still intense to damage tablelands like Dongzhi,as the most complete tableland,when high intensity storm events happened in the region.Research specially investigating gully-head retreat in the region is hard to found in the past decades years.At present,it is not clear that how land utilization transformation affects gully-head retreat process.Gully-heads on typical grassland and shrub-grass land,naturally restored from abandon farmland,and farmland,as a control,were built to investigate their retreat processes.Artificial simulated rainfall combined with scouring experiments were conducted to simulate the process of gully-head retreat and three dimensional reconstruction based on photos technology was used to monitor gully morphology.Differences were analyzed among soil physical-chemical properties and roots distribution characteristics from gully-heads in the three kinds of lands.Effects of land utilization and tableland gradient and gully-head height were illuminated on runoff and sediment yielding process,contribution rate of sediment from tableland,erosion by hydrodynamic and gravitational force as well as gully-head morphology evolution in the process of gully-head retreat.Mechanism of action was revealed of land utilization on gully-head retreat.It may provide important scientific implication for controlling gully to project tableland and establishment of soil erosion model in the region..The results showed that:Average runoff rates and sediment concentrations varied in ranges of 14.060 14.750L·h-1 and 0.054 0.077 g·mL-1.Benefits of runoff and sediment reduction were17.50% 21.91% and 70.37% 71.93% on grassland,and,15.77% 27.38% and56.58% 62.96% on shrub-grass land.Both runoff rate and sediment concentration increased with rise of tableland gradient and gully-head height,they increased by 4.91% and 41.80% onfarmland,and,21.67% and 45.81% on shrub-grass land in the plots with a tableland gradient of 9 compared to the plots with a gradient of 3,and they also raised by 4.15% and 40.74% on farmland,and,14.86% and 65.00% on shrub-grass land in the plots with a gully-head height of 1.5m compared to the plots with a height of 1.2m.Higher variation coefficients of sediment concentration were found on grassland and shrub-grassland with increases by67.81% 95.31% and 41.16% 155.93% respectively compared to the coefficient on farmland.Sediment from tableland contributed to sediment from plot with a rate ranged from12.70% to 26.31% on farmland,lower rates were found on grassland and shrub-grassland under the same test condition with decreases by 24.76% 43.09% and 52.25% 62.18%.

Mots clés : Gully head-ward erosion; Gully Region of Loess Plateau; Land-use; Gravitational erosion; Morphological Evolution;

Présentation (CNKI)

Page publiée le 30 janvier 2018