STUDY ON ANALYTICAL MODEL OF RUNOFF-EROSION DUE TO RAINFALL IN BRAZILIAN SEMI-ARID REGION

利用物理模型分析了巴西东北部半干旱区降雨引起的径流侵蚀特征。本研究分为三个部分：径流侵蚀模型、模型参数最优值的确定、模型在田间的应用。主要结论如下：1。利用运动波理论对径流侵蚀物理模型进行了分析，在模型参数合理的情况下，可以很好地模拟地表水流和超降雨河道水流对土壤表面的侵蚀速率。2 .模型参数最优值的确定研究：模型参数中的4个主要参数，即降雨影响下土壤可脱性Ki、剪切应力下土壤可脱性Kr、携沙系数a和土壤湿张参数Ns，采用改进的遗传算法，结合试验场观测数据，得到了较好的优化结果。将该模型应用于巴西和松山伊什勒河流域的农田径流侵蚀数据的研究，结果表明该模型具有较好的分析效果，并通过改进遗传算法对模型参数进行了优化。

THE CHARACTERISTICS OF RUNOFF-EROSION DUE TO RAINFALL IN THE SEMI-ARID REGION OF NORTH-EAST BRAZIL, WERE ANALYSED BY A PHYSICAL MODEL. THIS STUDY CAN BE DIVIDED INTO THREE PARTS: RUNOFF-EROSION MODEL, DETERMINATION OF THE OPTIMAL VALUES OF MODEL PARAMETERS, APPLICATION OF THE PROPOSED MODEL TO THE FIELDS. MAIN COCLUSIOS ARE AS FOLLOWS:1. STUDY ON PYSICAL RUNOFF-EROSION MODELSURFACE FLOW AND CHANNEL FLOW OF EXCESS RAINFALL ARE ANALYSED BY THE KINEMATIC WAVE THEORY AND THE EROSION RATE OF SOIL SURFACE WITH THE FLOWS ARE SIMULATED WELL IF THE MODEL PARAMETERS ARE PROPERLY GIVEN.2. STUDY ON DETERMINATION OF THE OPTIMAL VALUES OF MODEL PARAMETERSVALUES OF FOUR MAIN PARAMTERS OF THE MODEL PARAMETERS, SOIL DETACHABILITY BY RAINFALL IMPACT Ki, SOIL DETACHABILTY FOR SHEAR STRESS Kr, COEFFICIENT FOR SEDIMENT ENTRAINMENT a, AND SOIL MOISTURE-TENSION PARAMETER Ns ARE OPIMISED WELL BY A MODIFIED GENETIC ALGORISM WITH OBSERVED DATA IN THE TEST FIELD.3. STUDY ON APPLICATION OF THE PROPOSED MODEL TO THE FIELDSRUNOFF-EROSION DATA FROM THE TEST FIELD IN BRAZIL AND ISHlE RIVER BASIN IN MATUYAMA ARE ANALYSED WELL BY THE PROPOSED MODEL WITH PARAMETERS OPTIMIZED BY THE MODIFIED GENETIC ALGORISM.