Flood flow simulations and return period calculation for the Kota Tinggi watershed, Malaysia

In setting design inflows to hydrodynamic models of flood flow along rivers, there can be a conflict between site-specific hydrological estimates of flow for a given return period and what the river model calculates as it routes flood hydrographs. This paper describes research carried out as part of the Flood Studies Update programme in Ireland, aimed at developing guidance on how to divide up river models and set the magnitude and timing of their inflows so that conditions in the model reach correspond to the expected design flood return period. A model for the joint distribution of flood peaks at pairs of catchments has been developed. The relationship between flood return periods is linked to physical differences between catchments. The model thus allows estimation of the statistical distribution of the flood return period expected at one site during a flood of specified return period elsewhere. A separate regression model predicts the relative timings of flood peaks on pairs of rivers. A summary of the resulting practitioner guidance is given, along with an overview of the testing of the method. The paper concludes with a discussion of the potential for application of the spatial dependence model to other problems in hydrology.

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Automatic Web Procedure for Calculating Flood Flow Frequency

Water ◽

10.3390/w11010014 ◽

2018 ◽

Vol 11 (1) ◽

pp. 14 ◽

Cited By ~ 2

Author(s):

Pierluigi De Rosa ◽

Andrea Fredduzzi ◽

Annalisa Minelli ◽

Corrado Cencetti

Keyword(s):

River Basin ◽

Return Period ◽

Peak Flow ◽

Curve Number ◽

Computational Procedure ◽

Difficult Problem ◽

Run Off ◽

Tiber River ◽

Flow Frequency ◽

Flood Flow

The estimated flood flow frequency in a particular cross-section of a riverbed for a given return period is a topic of great interest for its application in hydrological, geomorphological and hydrogeological fields. Nevertheless, to establish a one-to-one relationship between rainfall and peak flow is a difficult problem to solve, due to the great number of factors involved (intensity and distribution of rainfall, hydromorphological characteristics of the watershed, type and distribution of vegetation, soil saturation conditions, etc.). In Italy, the Tiber River Basin Authority has developed a method to evaluate peak flows in the watersheds within the Tiber Basin. The relationship between rainfall depth with an assigned return period (RP) and the duration of the event was determined using data from 165 gauging stations throughout the Basin and in the neighbourhoods with respect to rainfall from 1 to 24 h and/or from 1 to 5 days. To calculate the peak flow with an assigned RP in small watersheds (area < 100 km 2 ), the Tiber River Basin Authority proposed a methodology that combines the results of regional precipitation analysis of a duration from 1 to 24 h with the Curve Number method, which allows the volume of net rainfall (i.e., the rainfall that contributes to producing the peak flow) to be quantified. Such procedure includes the calculation of various parameters (run-off time, local rainfall and areal rainfall, net rainfall) in order to obtain the value of peak flow. To facilitate the use of this procedure, a WebGIS system has been developed, based on a series of scripts that calculate the values for the above parameters. The user only has to choose the point corresponding to the section of the channel in order to determine the peak flow and the return period. The computational procedure is performed using GRASS GIS that interfaces with the system using the standard WPS; the system returns to output a report with details of the various calculations of parameters and, as a final result, the value of requested peak flow.

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