Abstract
Abstract. Estimations of flood frequencies in small catchments are difficult due to a lack of measured discharge data. This problem is usually solved in the Czech Republic by hydrologic modelling when there is a reason not to use the data provided by the Czech hydrometeorological institute, which are quite expensive and have a very low level of accuracy. Another way is to use a simple method which provides sufficient estimates of flood frequency based on the available spatial data. A new methodology is being developed considering all important factors affecting flood formation in small catchments. The relationship between catchment descriptors and flood characteristics has been analysed first to get an overview of the importance of each considered descriptor. The results for different descriptors vary from a highly correlated relationship of an expected shape to a relationship which is opposite to that expected, mainly in the case of land use. The parameterisation of the methodology is also presented, including the sensitivity tests on each involved catchment descriptor and cross-validation of achieved results. In its present form, the methodology achieves an Radj2 value of about 0.61 for 10- and 0.60 for 100-year return periods.
Highlights
A methodology for the estimations of flood frequency in small catchments is being developed
The approach used for the development of the presented methodology in general applies similarity principles which have been discussed by many authors worldwide (Burn, 1997; Merz and Blöschl, 2005; Wagener et al, 2007; Patil and Stieglitz, 2012)
There are different regression-based methods which are similar to the method proposed by the authors of this paper. These methods adopt different procedures for parameter estimation, such as ordinary least square regression (OLS), weighted least square regression (WLS), and generalised least square regression (GLS), which is discussed by Stedinger and Tasker (1985) and further by Pandey and Nguyen (1999), who involved more parameter estimation methods such as least absolute value regression, robust regression and others
Summary
A methodology for the estimations of flood frequency in small catchments is being developed. The approach used for the development of the presented methodology in general applies similarity principles which have been discussed by many authors worldwide (Burn, 1997; Merz and Blöschl, 2005; Wagener et al, 2007; Patil and Stieglitz, 2012) These principles are usually applied in three ways: (i) for the direct estimation of flood quantiles, (ii) for the estimation of probability distribution parameters and (iii) for the estimation of hydrologic model parameters. There are different regression-based methods which are similar to the method proposed by the authors of this paper These methods adopt different procedures for parameter estimation, such as ordinary least square regression (OLS), weighted least square regression (WLS), and generalised least square regression (GLS), which is discussed by Stedinger and Tasker (1985) and further by Pandey and Nguyen (1999), who involved more parameter estimation methods such as least absolute value regression, robust regression and others. The shifts were excluded in the first step of model development presented in this paper, and will be included in the step
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