# Implementation of Climate Change Effects on Slope Stability Analysis
## 2 Design of Geo-Structures Considering Climate Change
### Water Net Infiltration  
Water infiltration and evaporation processes at the soil surface are generally controlled by the prevailing climatic conditions and the water content of the soil [24]. Water arrives on the slope surface in the form of precipitation, and some of this water is intercepted and evaporated by leaves, branches, and the forest floor, which is called interception. After the loss of interception, the precipitation water reaches the soil surface. Some of this water flows over the ground as overland runoff when the amount of precipitation exceeds the infiltration rate, and the rest infiltrates into the soil. Overland runoff on a slope depends on several factors, including the angle of the slope, vegetation, and roughness of the sloped surface. The rate of infiltration depends primarily on the hydraulic conductivity of the soil, which is not constant, but changes with soil suction. The total amount of water infiltrating into the soil has a significant effect on the pore pressure and stability of slopes. However, a significant portion of this water is removed through the soil surface as actual evaporation and through plant roots as transpiration. These two processes by which water moves upward from the soil surface are referred to as actual evapotranspiration. The maximum potential evapotranspiration rate can be calculated using climate parameters such as air temperature, relative humidity, wind speed, and net radiation. The actual evapotranspiration rate can then be estimated using the potential evapotranspiration rate, available soil water near the soil surface, and vegetation characteristics. The amount of water remaining in the soil after the actual evapotranspiration loss is referred to as net infiltration. The water net infiltration at the ground surface can be positive or negative based on the amount of actual evapotranspiration. Net infiltration is the actual amount of water that changes the storage within the slope and has potential to affect the pore water pressure and stability of the slope. The amount of net infiltration primarily depends upon precipitation, surface runoff and actual evaporation (Figure 1) and can be written as follows [24]:  
\[\text{NI}=\text{P}-\text{AE}-\text{AT}-\text{RO}=\text{P}-\text{ET}-\text{RO} \tag{1}\]  
where NI is net infiltration (mm/day), P is precipitation (mm/day), AE is actual evaporation (mm/day), AT is actual transpiration (mm/day), ET is evapotranspiration (mm/day) and RO is runoff (mm/day). \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Geo-Structure** & **Project Steps** & \begin{tabular}{c} **Criterias (with Climate** \\ **Change Adaptation)** \\ \end{tabular} & **Measures** \\ \hline \multirow{4}{*}{**New geo-structure**} & Feasibility study & & \\ \cline{2-4}  & Outlined design & Appropriate criteria (safety, \\  & Detailed design & applicability) & \
\begin{tabular}{c} New design \\ always \\ \end{tabular} \\ \cline{2-4}  & Execution & & \\ \hline \multirow{4}{*}{**Existing geo-structure**} & & The criteria of safety and & No measures \\  & & applicability are satisfied & \\ \cline{2-4}  & No project steps &
\begin{tabular}{c} The criteria of safety and \\ applicability are not satisfied \\ \end{tabular} & Re-design \\ \cline{2-4}  & & Reduced qualities of & \\ \cline{2-4}  & & structure or ground & \\ \cline{2-4}  & & Signs of damages and & Intervention \\ \cline{2-4}  & & structure failures & measures \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Design step, criteria and measures for new and existing geo-structures. To estimate NI at the soil surface, each of the components of the water balance must be accurately estimated. The computational procedures for determining each of the components of the water balance are complex and involve numerous assumptions [6]. Without AE, AT and RO, the value of net infiltration (NI) is equal to P. If the sum AE + AT + RO is equal to P or even higher, then NI is zero or negative.