Wes Marshall, P.E. University of Connecticut January 2007 CE 276 Site Design Introduction to Site Design Chapter 1 – Contours & Land Form

Chapter 1 Contours & Form

Contours The ability to visualize, analyze, and interpret landforms from contour maps is an essential skill (

Contours  What is a contour? An imaginary line connecting points of equal elevation  Contours on a topographic map is the most common & convenient way of representing land form Other methods: Physical models Computer models (Digital Terrain Models… DTM)

Visualizing Contours (Booth, Basic Elements of Landscape Architecture)

Visualizing Contours (

Visualizing Contours (

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Contour Characteristics  Contours are continuous lines creating closed figures Closure may not be shown within the map limits

Contour Characteristics  2 or more contour lines are required to indicate: 3-D forms Direction of Slope  Contour lines never cross except in rare circumstances (i.e. overhanging cliff)

Contour Characteristics  The steepest slope is perpendicular to the contour line This is because it has the greatest vertical change in the shortest horizontal distance  Thus, water flows perpendicular to contour lines

Contour Characteristics  Equally spaced contour lines indicate a constant, or uniform, slope As contour lines get closer together, the slope is getting steeper

Contour Characteristics  Contour lines never divide or split in the natural landscape However, at buildings or other structures, contour lines can give the appearance of splitting

Landforms Various types of landforms Ridge Valley Summit Depression Uniform Slope Convex and Concave slopes Gap Saddle

Ridge & Valley Ridge Raised elongated landform typically with a highpoint Valley Elongated depression forming between the space of two ridges  The two are interconnected because the ridge side slopes create the valley walls

Summit & Saddle Summit Hill or mountain containing the highest point elevation Represented by a set of concentric contours with the highest contour at the center Saddle Dividing point between two valleys (or swales) The high point between the two valleys and a low point between the ridges creating the valleys

Saddle, Summit, & Valley

Depression Contains the lowest point elevation Represented by a set of concentric contours with the lowest contour at the center  In order to distinguish from summits, you need to know the directions of the slopes

Uniform Slope Constant slope Contour lines spaced at equal distances  More typical in constructed landscapes than in the natural environment

Convex Slope Contour lines are spaced at decreasing distances in the downhill direction Slope is flatter at higher elevations and progressively steeper at the lower elevations

Concave Slope Contour lines a re spaced at increasing distances in the downhill direction Slope is steeper at higher elevations and progressively flatter at the lower elevations

Convex & Concave Slopes

Concave Slope & Summit

Convex Slope & Valley

Gap Distinct break in ridgeline

Water Gap

How to Draw a Section a) Indicate section plane b) Draw lines parallel to cutting plane to represent vertical scale c) Project plan view contour elevations onto section view d) Connect the dots plan view section view

Questions  True or False?All contours eventually close on themselves.  A _________ slope is said to occur when contour lines are spaced at increasing distances in the downhill direction.  True or False? Water flows parallel to contour lines.  True or False? For the same scale and contour interval, the steepness of slope increases as the map distance between contours increases.