植被根系对干旱内陆河流岸坡冲刷过程影响的模拟研究

Simulation Study on the Effect of Vegetation Root Systems on the Scour Process of River Bank Slope in Arid Inland

为探讨植被根系对干旱内陆河流岸坡冲刷过程的定量影响,以塔里木河为研究对象,采用BSTEM模型模拟分析的方法,模拟了8个典型岸坡在2016—2017连续2个水文年的冲刷过程,重点分析骆驼刺、红柳、芦苇、甘草、胡杨、白刺等6种典型荒漠植被根系对河岸冲刷过程的定量影响。结果表明:(1)塔里木河河岸崩塌基本发生于落水期和枯水期,岸坡稳定性在水文年内呈周期性变化,枯水期和涨水期安全系数F s略有波动,整体上呈稳定状态,河岸稳定,在洪水期高水位处F s短暂升高,随后随着水流的冲刷淘蚀以及水位下降,F s不断下降,直至河岸崩塌,随后进入下一个水文年的循环;(2)植被根系在不同水位时期对稳定性的提升效果不同,具体表现为洪水期>涨水期>枯水期>落水期;(3)不同植被对稳定性增强的差异也较大,表现为白刺>骆驼刺>甘草>红柳>胡杨>芦苇;(4)植被根系在不同水位时期对河岸冲刷量的减少效果不同,表现为落水期>洪水期>涨水期>枯水期。根系存在河岸冲刷量减少0.77%~49.36%,且不同植被对河岸冲刷量的减少效果也不同,表现为白刺>甘草>红柳>骆驼刺>胡杨>芦苇;不同植被对于安全系数稳定效果和对于岸坡冲刷量减少效果基本一致,研究结果可为塔里木河河道生态治理提供理论参考。

To study the vegetation root systems of the arid inland river bank slope erosion quantitative influence of the process,taking the tarim river as the research object,the BSTEM model was adopted to simulate the scour process of 8 typical bank slopesin two successive hydrological years 2016—2017.The quantitative effects of the root systems of six typical desert vegetation species(Alhagi sparsifolia(AS),Tamarix ramosissima(TR),Phragmites australis(PA),Glycyrrhiza uralensis(GU),Populus euphratica(PE),Nitraria tangutorum(NT))on the riverbank scour were analyzed.Results demonstrated that:(1)The collapse of the Tarim River bank basically occurred in recession period and dry period.The stability of bank slope changed periodically in hydrological years.The safety factor F s fluctuated slightly between dry period and level rising period,and was stable on the whole and riverbank.F s increased briefly at the high-water level during the flood period.Subsequently,with the erosion of water flow and the decline of water level,F s continued to decline until the riverbank collapses,and then entered the cycle of the next hydrological year.(2)The improvement effect of vegetation root systems on the stability was different at different water level periods,which was as follows:flood period>level rising stage>dry period>recession stage.(3)There was a significant difference in stability enhancement among different vegetation types,as follows:NT>AS>GU>TR>PE>PA.(4)At different water lever periods,the reduction effect of vegetation root systems on the amount of riverbank flushing was different,recession stage>flood period>level rising stage>dry period.The root system reduced the amount of riverbank flushing by 0.77%to 49.36%,and the effect of different vegetation on the amount of riverbank flushing was different,which was as follows:NT>GU>TR>AS>PE>PA.The effect of different vegetation on the stability of safety factor and the reduction of bank slope washing volume was basically the same.The results can provide theoretical reference for the ecological management of Tarim River.