Watershed spatial analysis and morphometry:
(A) Watershed delineation -> (II) McCuen: Richard H. McCuen formalized systematic hydrologic procedures and algorithms for delineating drainage divides and topographic watershed boundaries.
(B) Watershed coding -> (IV) AISLUS: The All India Soil and Land Use Survey (AISLUS) developed the national alphanumeric 6-stage watershed codification system for India (Water Resource Region, Basin, Catchment, Sub-catchment, Watershed, Sub-watershed).
(C) Watershed geometry -> (I) Bernard: Merrill M. Bernard introduced geometric models relating shape, length, and width to flood hydrographs (form factor / elongation ratio).
(D) Stream order -> (III) Horton: Robert E. Horton established the foundational laws of stream orders, drainage composition, and bifurcation ratios in quantitative geomorphology.
Hence, the correct match is (A) - (II), (B) - (IV), (C) - (I), (D) - (III).