The Course Rating and Slope Rating is the evaluation of the playing difficulty of the course for the scratch player and the bogey player respectively under normal playing conditions. The ratings are based on a formula which uses a combination of the effective playing length of each hole – which in turn takes in to account factors such as prevailing wind, elevation changes and forced lay ups – and 10 ‘obstacle factors’. The latter are listed as: topography; fairway; green target; recoverability and rough; bunkers; crossing obstacles; lateral obstacles; trees; green surface and psychology.
Courses evolve over time. Trees and bushes grow, others die. Tweaks to the layout are made for drainage, to ease a pace of play, to make the routing safer, or just because the greens committee perceives an improvement to the existing layout. Ditches get covered up, bunkers get reshaped, taken out or introduced. The contours of a green are changed to facilitate drainage or to provide more potential pin positions. That sort of thing.
Newly built courses are most likely to undergo rapid change, as they grow up and bed in and the practicalities of the architect’s design become apparent.
Appendix G to The Rules of Handicapping issued by the R&A states that: “Course Ratings must be reviewed periodically and revised and reissued as necessary. New golf courses can change frequently during the first years after construction and must be re-rated within five years of the initial rating date. Thereafter, golf courses must be re-rated at least once every 10 years.”
When the club makes a permanent change to a course it is required to “notify the Authorized Association,” as permanent changes “require the Authorized Association to review the current Course Rating and Slope Rating and to determine whether a re-rating is necessary.”
If a significant temporary change is made that may affect the Course Rating – such as introducing a forward temporary green or tee on hole – the “Handicap Committee must notify the Authorized Association” who “will determine whether scores made under such conditions are acceptable for handicap purposes, and whether the Course Rating and Slope Rating should be modified temporarily."
