Module 4: Flood and Drought
In this module, we will discuss the causes, implications and ways to characterize and predict what are often referred to as ‘extreme events’ in hydrology: floods and droughts. Such events play important roles in natural ecosystems and are a major concern for society, with significant impacts on the economy, ecosystem health and services, as well as human health. To gain a broader perspective, we will discuss floods and droughts within the more general topic of hydrologic variability. We will look beyond simple metrics like average annual rainfall to instead think about the full distribution of ‘events’ that characterize the hydrology of an area. The goals of this module are to expose you to the basic concepts of floods and droughts, develop an understanding of how we characterize ‘normal’ and ‘extreme’ hydrologic events, and gain some perspective on the consequences of floods and droughts for society and ecosystems. As part of this, you will become familiar with terms such as stationary versus non-stationary conditions, return period (a.k.a., recurrence interval), exceedance probability, and probability density function.