The Ernst drainage equation is especially applicable for subsurface drain spacing in:
Options:
(A) Layered (stratified) soils where horizontal, vertical, and radial flow components occur through subsoil horizons with different hydraulic conductivities
(B) Strictly homogeneous and isotropic deep sand
(C) Cracked vertisols during drought
(D) Paddy soils under standing water only
Answer Key:
A
Step-by-Step Solution & Explanation
Ernst's method partitions total hydraulic head loss into three distinct geometric flow regimes: vertical flow through the top layer ($h_v$), horizontal flow through the intermediate layer ($h_h$), and radial flow entering the drain tube ($h_r$).