cfgSurfaces adds clutter configuration for ground detail texture (GDT) file names in the data\ directory. We also configure how rough the terrain is, what sound is played when driving/walking on it etc.

a3\map_data\config.cpp/cfgSurfaces:

class CfgSurfaces
{
	class Default{};
	class Water{};
	class GdtStratisGreenGrass: Default
	{
		access = 2;
		files = "gdt_strgreengrass_*";
		character = "StratisGreenGrassClutter";
		soundEnviron = "grass";
		soundHit = "soft_ground";
		rough = 0.08;
		maxSpeedCoef = 0.9;
		dust = 0.15;
		lucidity = 4;
		grassCover = 0.05;
		impact = "hitGroundSoft";
		surfaceFriction = 1.7;
		maxClutterColoringCoef = 1.35;
	};
	class GdtStratisRocky: Default
	{
		access = 2;
		files = "gdt_strrocky_*";
		character = "StratisRockyClutter";
		soundEnviron = "gravel";
		soundHit = "hard_ground";
		rough = 0.12;
		maxSpeedCoef = 0.85;
		dust = 0.4;
		lucidity = 1.5;
		grassCover = 0.02;
		impact = "hitGroundHard";
		surfaceFriction = 1.9;
		maxClutterColoringCoef = 1.35;
	};
	// etc ...
};

See also how_cfgsurfaces_cfgsurfacecharacters_and_clutter_work.