Jyrkkyys

Jyrkkyys is a Finnish noun meaning steepness or a steep slope. It is derived from the adjective jyrkkä, meaning steep, with the noun-forming suffix -syys. The term is used in geography, geomorphology, engineering, and related fields to describe how steep a surface or terrain is.

In geographic and geomorphological contexts, jyrkkyys refers to terrain steepness and can be expressed as an angle of inclination (degrees) or as a gradient (percent grade, rise over run). Slopes are often categorized for practical purposes in land-use planning, forestry, and hazard assessment. The choice of measurement depends on the objective: angles are intuitive for navigation, while gradients are convenient for engineering calculations and modeling.

In engineering and planning, higher jyrkkyys indicates greater challenges for construction, road design, and drainage. Steeper slopes can increase erosion, runoff, and landslide risk, affecting soil stability and long-term infrastructure performance. Maps and digital elevation models are commonly used to derive slope values, enabling risk zoning and the design of retaining structures, cut-and-fill works, and drainage systems.

In mathematics and physics, the analogous concept is the slope or gradient of a line or surface; for a straight line, steepness equals the tangent of the angle with the horizontal. While jyrkkyys is the Finnish term, the underlying idea is universal, and in Finnish contexts it particularly emphasizes terrain characteristics.

Related terms include steepness, slope, gradient, and grade.