Preprints
https://doi.org/10.5194/hess-2017-252
https://doi.org/10.5194/hess-2017-252

  29 May 2017

29 May 2017

Review status: this discussion paper is a preprint. It has been under review for the journal Hydrology and Earth System Sciences (HESS). The manuscript was not accepted for further review after discussion.

On the Relationship Between Flood and Contributing Area

Christopher Spence1 and Samson Girma Mengistu2 Christopher Spence and Samson Girma Mengistu
  • 1Environment and Climate Change Canada, Saskatoon, SK, Canada
  • 2University of Alberta, Edmonton, AB, Canada

Abstract. While it is well known that the vast majority of the time only a portion of any watershed contributes runoff to the outlet, this extent is rarely documented. The power-law form of the streamflow and contributing area (Q-Ac) relationship has been known for a half century, but it is uncommon for it to be quantified or its controls evaluated. In this study a semi-distributed hydrological model (MESH-PDMROF) that can simulate contributing area and streamflow was employed to compare contributing area and flood frequency distributions in a southern Manitoba, Canada catchment and test the hypothesis that the relationship between a catchment’s floods and contributing area is a power function that influences the form of regional flood-area relationships. The model simulated streamflow reasonably well (Nash Sutcliffe values = 0.62). Modelled estimates of the area contributing to the mean annual flood were much lower (0.3) than those derived from independent topographic analysis (0.9) described in earlier literature, even after bias and error corrections. Estimates of the coefficient and exponent of the Q-Ac power law function ranged from 0.08–0.14 and 0.9–1.12, respectively. Lower exponent values of regional flood frequency curves suggest they are a construct of Q-Ac curves from individual basins. The non-linear nature of this relationship implies any contributing area change will have a profound impact on flood magnitude. The mean annual flood of the major river in this region, the Red, has increased 33 % since 1987. Applying the coefficient and exponent ranges above suggests this is associated with an expansion in contributing areas of 29–38 %. There are implications for the attribution of causes and mitigation of nutrient transport from regional watersheds. However, how physiography and land and water management could change Q-Ac power law exponents is poorly known and MESH-PDMROF does not provide explicit estimates of the spatial distribution of contributing area. These are areas encouraged for future research.

Christopher Spence and Samson Girma Mengistu

 
Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Christopher Spence and Samson Girma Mengistu

Christopher Spence and Samson Girma Mengistu

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Short summary
This research summarizes the application of a hydrological model to determine the relationships between streamflow and the area that contributes water to it. The model performed well. Results show that the frequency of streamflow events and with which areas contribute are not necessarily the same. There are implications from this research for determining the sources of water and nutrients available downstream in lakes vulnerable to eutrophication.