Department of Civil Engineering, Monash University, Wellington Road, Clayton 3800 Victoria, Australia.
Water Res. 2010 Apr;44(8):2487-98. doi: 10.1016/j.watres.2010.01.022. Epub 2010 Jan 29.
The first flush in urban runoff has been an important, yet disputed phenomenon amongst many researchers. The vast differences in the evidence could be solely due to limitations of the first flush current definition and the approach used for its assessment. There is a need for revisiting the first flush theory in the light of its practical applications to urban drainage management practices. We propose that a catchment's first flush behaviour is to be quantified by the runoff volume required to reduce a catchment's stormwater pollutant concentrations to background levels. The proposed method for assessment of this runoff volume starts by finding the average catchment pollutant concentrations for a given increment of discharged volume using a number of event pollutographs. Non-parametric statistics are then used to establish the characteristic pollutograph by pooling statistically indifferent runoff increments (known as slices) together. This allows the identification of the catchment's initial and background pollutant concentrations and for quantification of the first flush volume and its strength. The novel technique was used on seven catchments around Melbourne, Australia, with promising results. Sensitivity to the chosen increment of runoff (for which mean concentrations are calculated) indicated that when dealing with discrete flow-weighted water quality data, a suitable slice size should closely match the flow-weighting of samples. The overall sensitivity to runoff increment and level of significance was found to be negligible. Further research is needed to fully develop this method.
城市径流初期冲刷是许多研究人员关注的一个重要但存在争议的现象。证据之间存在巨大差异，这可能仅仅是由于初期冲刷的当前定义和评估方法存在局限性。有必要根据其在城市排水管理实践中的实际应用重新审视初期冲刷理论。我们提出，流域的初期冲刷行为可以通过减少流域暴雨污染物浓度至背景水平所需的径流量来量化。评估该径流量的建议方法首先通过使用多个事件污染图找到给定排放量增量的平均流域污染物浓度来开始。然后使用非参数统计数据通过将统计上无差异的径流增量（称为切片）组合在一起，建立特征污染图。这允许确定流域的初始和背景污染物浓度，并量化初期冲刷量及其强度。该新技术在澳大利亚墨尔本周围的七个流域进行了测试，结果令人鼓舞。对所选径流量增量（用于计算平均值）的敏感性表明，在处理离散流量加权水质数据时，合适的切片大小应与样本的流量加权密切匹配。发现对径流增量和显著性水平的总体敏感性可以忽略不计。需要进一步的研究来充分开发这种方法。
