I want to evaluate extreme events in a basin specially perennial rivers , African Rivers Case i try to use the statistical methods of extreme analysis like the POT and general Pareto methods. but the main challenge face to me is that how can I select the specific thresholds to evaluate with out a given depth of flow that results in a flood or a drought? How can i define the thresholds, based on the data i have? If you look at the observed runoff for one of stations in the catchment, how will determine the times when there were extreme events? floods or drought? if any one know some methods please put here with some references,thank you
This may help, but I dont know data you have. If you read and understand David Rosgen's papers and books on www.wildland hydrology.com you will know how to look for bankfull features and classify streams into their appropriate morphological class. If you know bankfull flow and its relation to the stream bank, you will have a basis in many instances to evaluate whether the flooding was possibly normal, infrequent or extreme. If your stations are not gauging stream stage (heights), transducers such as sold by Global Water or Hobo are good investment to get this data, and set up staff gauges so you will be able to log stream stage when you visit or make measurements. There are various ways to consider extreme events, and I am not going to suggest which may be best, just find what works with your data and document your approach(s).
thank you william, but for my case study, it is a general for African rivers using time series data which have a complex topographic with perennial stream flow ?
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