Topography consists of the physical aspects of the surface of the earth and includes such features as relief and drainage, vegetation, surface materials, and cultural features.

Relief and Drainage

RELIEF is the term given to the differing areas of elevation and depression on the surface of the earth. DRAINAGE refers to those areas of surface depression that serve as water runoffs or collection points, such as marshes, swamps, streams, rivers, ponds, and lakes. Knowledge of the general shape of the land is gained through a detailed study of the relief and drainage features. The steepness of slopes; the height and size of hill masses; the depth, the width, and the length of drainage features; and the sizes of valleys and draws are major features to consider when studying the terrain of a given area. These irregularities in the surface of the earth influence tactics by the degree of observation they provide the opposing forces, the ease or difficulty of movement, and the degree of protection provided against enemy fire. Flat ground provides equal observation for the opposing forces; normally, high ground in rolling or mountainous terrain provides for better observation.

Any advances made parallel to a series of ridges or to a river or stream are mechanically easier than movement perpendicular to them. The steepness of a slope may limit movement; tanks, for instance, cannot climb slopes greater than 30 degrees.

Flat ground offers little protection against enemy fire, but rolling ground will, particularly against flat-trajectory weapons.

Vegetation

Vegetation is classified for practical purposes as either NATURAL or CULTIVATED. Natural plant life includes all types of grasses, bushes, and trees growing without the assistance of man; cultivated vegetation includes all crops and orchards tended by man. Density, height, and types of growth, as well as the diameter of tree trunks, are significant features when you are studying vegetation.

Although vegetation may restrict vision, it offers concealment and limited cover. Of course, the thicker the growth, the harder it is for the forces to move about.

Surface Materials

Surface materials are studied to determine the trafficability of an area. "Trafficability" is defined as the ability of a soil in its normal state to support vehicular traffic moving cross-country or on unimproved roads and trails. In general, all types of soil, except very loose sand, afford good trafficability when dry. However, soils are seldom completely dry. Water may change soil from a hard, baked clay to slippery, impassable mud within a matter of minutes, especially in tropical areas. Another

aspect to consider, along with the types and condition of the soils, is the slope of the ground, the type of vegetation, and the roughness of the surface.

Cultural Features

CULTURAL FEATURES include all the works of man, such as towns, airfields, roads, railroads, and bridges. For military purposes, man-made features are considered an integral part of terrain. Cities and towns are frequently the objectives of an attacking force. For tactical purposes, cultural features may be centers of resistance as well as physical obstacles in your path. Roads, railroads, and bridges are vulnerable links in logistics and communication networks.