--- title: "Contour gradient and characteristics" subject: "Surveying II" chapter: 4 key: "semester_4/surveying_ii:contour-gradient-characteristics" source: https://www.bctengineer.com/q/semester_4/surveying_ii/contour-gradient-characteristics site: BCT Engineering --- # Contour gradient and characteristics Surveying II · Chapter 4: Contouring - Asked in: 2068 Bhadra, 7 marks - Video: [Contour Gradient | Ground Horizontal Equivalent| How to draw contour gradient](https://www.youtube.com/watch?v=0EpEtsYD_j8) — EngineeringMantra - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_4/surveying_ii/contour-gradient-characteristics - Whole chapter: https://www.bctengineer.com/md/semester_4/surveying_ii/chapter-4 ## Question What is contour gradient? Write characteristics of contours with suitable sketches. ## Short answer Contour gradient is a line of uniform slope that cuts successive contours at equal horizontal distances (gradient = contour interval / horizontal equivalent). Characteristics: contours are closed curves of equal elevation; they never cross except at overhanging cliffs; spacing indicates slope; they bend upstream at valleys and downstream at ridges; concentric contours with higher inside show a hill, lower inside a depression. ## Answer #### Contour gradient **Contour gradient** is the line of constant slope (uniform gradient) that cuts the contours at the same horizontal equivalent. It is laid on the ground to fix the route of a road, railway, canal or pipe line. The gradient = CI / HE = 1 in (HE/CI). #### Characteristics of contours 1. **Contours are closed curves.** Every contour must close on itself, either inside the map or outside it. It cannot start or end abruptly. 2. **All points on a contour have the same elevation.** 3. **Contours never cross each other**, except at an overhanging cliff or a cave. Two contours of different elevation cannot meet or cross because one point cannot have two elevations. 4. **Contours of different elevations do not unite** to form one line, except at a vertical cliff, where they coincide and appear as one line. 5. **Closely spaced contours indicate a steep slope; widely spaced contours indicate a gentle slope.** Equally spaced contours indicate a uniform slope, and straight, equal and parallel contours indicate an inclined plane. 6. **Contours cross ridge lines and valley lines at right angles.** The direction of the steepest slope is at right angles to the contour. 7. **A set of concentric closed contours** with the higher value inside represents a hill; with the lower value inside it represents a depression (pond or pit). 8. **Contours bend as V or U shapes across a ridge and a valley.** For a ridge (spur) the bend of the contour points towards the lower ground; for a valley the bend points towards the higher ground. 9. **Contours of the same elevation may reappear** on the other side of a ridge or a valley, so one contour value can appear twice on a map. 10. **A contour cannot lie between two contours of higher (or lower) values** unless it closes on itself (hill or depression). 11. **A saddle (col)** is shown by the closed contours of two hills on opposite sides, with lower ground (valleys) on the other two sides; the saddle point lies at the neck between the hills. ```text HILL DEPRESSION .--100--. .--100--. / .-110-. \ / .--90-. \ | / (120) \ | | / (80) \ | \ '-----' / \ '-----' / '-------' '-------' RL rises to the centre RL falls to the centre ``` ```text RIDGE (v points downhill) VALLEY (^ points uphill) 130 \ / 120 /\ \ / / \ 120 \ / 110 / \ \_/ / \ 110 \ / 100 / \ \___/ high ground at top high ground at top ``` ```text Steep slope Gentle slope Uniform slope (close) (wide apart) (equal spacing) ----100 ----100 ----100 ----101 ----101 ----102 ----102 ----103 ----101 ----103 ``` ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What is a contour gradient? A. The vertical distance between two contours B. A line of constant slope that cuts successive contours at the same horizontal equivalent C. A line joining points of equal elevation D. The steepest line on a hill Answer: B. A contour gradient is a line of uniform slope laid on the ground to fix a route, cutting contours at equal horizontal equivalent. (Key point: Contour gradient definition) 2. The gradient of a contour gradient line is given by: A. HE / CI B. CI x HE C. CI / HE D. CI + HE Answer: C. Gradient = vertical rise / horizontal distance = CI / HE, i.e. 1 in (HE/CI). (Key point: Gradient formula) 3. Why can two contours of different elevation not cross or meet (except at cliffs or caves)? A. Contours must always be parallel B. A common point would have two different elevations C. Contour interval would become zero D. Contours are drawn only in straight lines Answer: B. All points on a contour have the same elevation, so a point shared by two different contours would need two elevations, which is impossible. (Key point: Contours never cross) 4. Closely spaced contours on a map indicate: A. A gentle slope B. A flat plain C. A steep slope D. A depression only Answer: C. Close spacing means a large level change over a short horizontal distance, i.e. a steep slope. (Key point: Slope and spacing) 5. At a ridge (spur) the bend of a contour points: A. Towards the lower ground B. Towards the higher ground C. Along the ridge line towards the summit D. Parallel to the ridge line Answer: A. For a ridge the contour bend points toward lower ground; for a valley it points toward higher ground. (Key point: Ridge and valley bends) ## Related in Surveying II - [Characteristics of contours with sketches](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Acontour-characteristics-sketches) — Surveying II, chapter 4, asked 5× - [Contour terms and characteristics with sketch](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Acontour-terms-characteristics) — Surveying II, chapter 4, asked 3× - [Contour characteristics, guide points A and B](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Acontour-characteristics-six-guide-points) — Surveying II, chapter 4 - [Contour index, fixing contours between 1240.12 and 1264.32](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Acontour-index-fixing-uniform-slope-points) — Surveying II, chapter 4 - [Contour gradient, index contour, interval factors](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Acontour-gradient-index-interval-factors) — Surveying II, chapter 4 - [Contour characteristics and uses of contour map](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Acontour-characteristics-uses) — Surveying II, chapter 4