**4. Conclusions**

This chapter presents hydrological modeling results using various types of design hyetographs and their influence on the design discharge values. The presented methods can be used for the design peak discharge value or even complete design flood hydrograph definition in case of ungauged basins or in cases where very little discharge data are available. The HEC-HMS model and the unit hydrograph theory were used in the modeling process. This model is frequently used in the hydrologic engineering practice around the world. Surface runoff was calculated using various design hyetographs where the focus was arbitrarily set on the 10-year return period. Based on the presented results, we can propose general guidelines on how to determine the design hyetograph in case of ungauged (small size, i.e., less than 20 km<sup>2</sup> ) catchments:

**Acknowledgements**

provision.

**Author details**

**References**

Nejc Bezak\*, Mojca Šraj and Matjaž Mikoš

238. DOI: 10.1002/hyp.10145

1999. p. 338

p. 185

284. DOI: 10.1016/j.jhydrol.2016.02.058

Cambridge University Press; 2013. p. 490

\*Address all correspondence to: nejc.bezak@fgg.uni-lj.si

The results of the study are part of the Slovenian national research project J2-7322: "Modelling hydrologic response of nonhomogeneous catchments" and research program P2-0180: "Water Science and Technology, and geotechnical engineering: Tools and methods for process analyses and Simulations, and development of technologies" that are financed by the Slovenian Research Agency (ARRS). We wish to thank the Slovenian Environment Agency for data

Design Rainfall in Engineering Applications with Focus on the Design Discharge

http://dx.doi.org/10.5772/intechopen.70319

13

Faculty of Civil and Geodetic Engineering, University of Ljubljana, Ljubljana, Slovenia

Journal. 2014;**59**(5):959-977. DOI: 10.1080/02626667.2013.831174

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[3] Šraj M, Bezak N, Brilly M. Bivariate flood frequency analysis using the copula function: A case study of the Litija station on the Sava River. Hydrological Processes. 2015;**29**(2):225-

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[6] USWRC (United States. Interagency Advisory Committee on Water Data. Hydrology Subcommittee). Guidelines for Determining Flood Flow Frequency. 1st ed. Reston: US Department of the Interior, Geological Survey, Office of Water Data Coordination; 1982.

[7] Blöschl G, Sivapalan M, Wagener T, Viglione A, Savenije H, editors. Runoff Prediction in Ungauged Basins: Synthesis across Processes, Places and Scales. 1st ed. Cambridge:


Using aforementioned procedure of design hyetograph determination and selected hydrological model, one can calculate either the complete design flood hydrograph or just design peak discharge values.

Furthermore, next conclusions can be made based on the presented results:

