How does climate changes affect the design storms?

As we know, we create the design storm according to the IDF of precipitation amounts. According to the climate change and global warming effects, the amount of precipitation is directly decreases or increases, indeed the intensity and duration of rainfall's pattern would be changed, therefore the design storms is affected by these changes.

Stormwater is usually designed to store-and-release the runoff of extreme rainfall events based on a selected return period, e.g., 100 years. The design storm is typically a recorded historical event or one that is extracted from historical intensity-duration-frequency (IDF) curves. In essence, the selected storm and the resulting design are deterministic.

As we know climate change plays an crucial role in changing hydro-meteorological variables (precipitation, evapotranspiration, temperature and etc), so it can easily effect on hydrological cycle and available water resources (Piao et al., 2010; Arnell, 1999), water demand (Doll, 2002; Grouillet et al., 2015), land use (Wheeler and Braun, 2013), risk of extreme events (Cai et al., 2014; Monier and Gao, 2015), and the viability of water infrastructure. The hydro- meteorological research community has made significant strides in the direction of quantifying possible climate change impacts on precipitation (Rudolph et al., 2012; Rana et al., 2014), streamflow (Yang et al., 2014), temperature (Lauri et al., 2012), reservoir operation (Raje and Mujumdar, 2010), flood risks (Veijalainen et al., 2010), and droughts (Jenkins and Warren, 2015).

Indeed, these changes can easily interfere on the pattern of rainfall, flow of rivers, altering in runoff's pattern, changing in the extreme events (flood's risk and stormwater), and changing the value of discharge in different season. So, the distribution of rainfall will change, and also all of them directly changes the design storm and stormwater.

Recent studies on climate change indicated that the return period of an annual maximum precipitation (AMP) amount will decrease significantly by the end of the 21st century while the frequency of extreme rainfall events will increase (IPCC, 2013). Consequently, climate change is projected to have significant effects on urban drainage and design considerations of storm water collection infrastructure (Willems, 2013; Watt and Marsalek, 2013). This led to investigations of changes to IDF curves, used for urban drainage designs in many places under climate change.

Moreover, anthropogenic changes, urbanization, and deforestation in the watershed have amplified the effects of flooding. The consequences of flooding are devastating, and cause long-term as well as short-term effects. The peak flow, which is the main design parameter of a drainage system, is expected to increase due to climate change over its service life. The collective effects of projected climate change on an urban stormwater system are amplified by the fact that the service life of urban drainage infrastructure is much longer.