Stream Flow Analysis of the Big Sioux River Just South of Brookings, South Dakota

Floods are the most common type of natural disaster in the world and one of the most damaging. Changes in climate conditions such as precipitation and temperature are causing changes in stream flow. This means that in order to better understand flooding and possibly develop a system for making flood predictions, stream flow needs to be analyzed more closely. The primary objective of this thesis is to analyze the Big Sioux River just south of Brookings, South Dakota, both annually and seasonally. The United States Geological Survey (USGS) has stream gauges placed in rivers and streams all over the United States. One of those gauges was installed in 1953 and is located in the Big Sioux River just south of Brookings, South Dakota and is the gauge that will be used for this study. The daily stream flow from October, 1953, to September, 2018, was selected as the time period of study. The stream flow data was grouped into yearly stream flow then classified as very wet, wet, average, dry and very dry for each year. Then the steam flow data was broken into four seasons for each year; fall, winter, spring and summer. The climate classification fit a log normal distribution with twenty-four years classified as average, sixteen classified as wet, seventeen classified as dry and the very wet and very dry classifications each having four years. The seasonal analysis showed that the spring months had the highest stream flow and the fall had the lowest stream flow. The streamflow analysis results were then compared to multiple other research projects, but the main comparison was to a study performed by Sadichya Amatya. That project focused on the development of climate scenarios based on precipitation analysis for five different locations in eastern South Dakota, including Brookings South Dakota. In comparing results, it was found that similar climate classifications were made between the two studies. However, in Amatya’s study she classified eight-year periods of precipitation rather than each individual year. This proved to be less useful than analyzing each individual year for flood prediction purposes but did allow an analysis of how a wet or very wet 8-year cycle is related to high streamflows. In order to continue the process of making flood predictions, more research is suggested in the area of an analysis of precipitation data for the area, snow melt and runoff analysis, ground water analysis, stream height analysis and other stream studies