(1) Except as provided in Sentence (2), the topographic factor, Ct, shall be taken as 1.0.
(2) For buildings on hills or escarpments with slope, Hh/(2Lh), greater than 0.1 as shown in Figure 4.1.7.4., the topographic factor, Ct, shall be calculated as follows:
C_t = (1 + ΔS / C_t) · (1 + ΔS)
where,
ΔS = ΔS_max · (1 − |x|/(k L_h)) · exp(−α z / L_h)
where,
ΔSmax =applicable values from Table 4.1.7.4.,
x =horizontal distance from the peak of the hill or escarpment,
Lh =horizontal distance upwind from the peak to the point where the ground surface lies at half the height of the hill or escarpment, or 2Hh where Hh is the height of the hill or escarpment, whichever is greater,
z =height above ground, and
k and α =applicable constants from Table 4.1.7.4. based on shape of hill or escarpment.