Monday, January 12, 2009

Planning 1- Module 4: Natural Factors












Land Use


Traffic & Transit

Density, Zoning



Existing Buildings


Natural Features

Spatial Patterns

Visual Barriers



Base Map

Municipal or General Base Map

Poblacion or Urban Base Map

Base Maps for other Built-up Areas

Vicinity Map

Thematic or Analytical Maps

Contour Map

Soil Map

Slope Map

Hydro-geologic or Groundwater Map

Climate Map


Geologic processes which might have affected the site, its formation, and the type of bedrock below the surface of the soil.

To understand the processes that have occurred in the past, it is useful to review the historical evolution of a region.

The underlying geology, rock character and depth, fault lines

Bedrock is a consolidated rock material lying at various depths below all points of the earth’s surface.

The type and depth of bedrock presents many questions of its adequacy as a base for foundations of buildings, walls or roads.

Test borings on several locations on the site can provide the answers.

Surficial Geologic Materials extend above bedrock to the surface soil. May be porous and serve as acquifers.

Mass Movement of Land Surface by tectonic movement through crustal stress, shock by earthquakes, or movement caused by surficial processes, including rockfalls, landslides, mudflows, and soil creep

Mass Movement of Land Surface

- tectonic movement maybe caused along faults often accompanying earthquakes.

- Surficial processes power mass movement by force of gravity, often started by heavy rain that saturate rock and soil with water to the point where gravity can cause movement.


Description of landforms is physiography.

Branch of geology dealing with the origin and nature of landforms with emphasis on erosional processes is geomorphology.

Geomorphological processes:

- erosion and deposition along rivers

- erosion of cliffs by the sea

- rocks breaking away from mountain sides because of frost action on the joints.

- Landslips occurring where surface materials are not yet at a stable angle in relation to the local geological structure.


…irregularities of the earth’s surface.

…are derived from volcanic, glacial or erosional processes.


- Topographic maps show locations and elevations of natural as well as man-made features, relief and vegetation.

- Contours

- Patterns of landforms – slopes, circulation possibilities, access points, barriers, visibility

- Unique features.

Slope Analysis

- Aids in recognizing areas suitable for building locations, roads, parking, or play areas.

- It may show if construction is feasible.

- Parking lot should be below 5% or regrading is to be done.

Breakdown of grades:

0 - 3% level to very gently sloping

3 - 8% rolling to hilly

8 - 18% gently sloping to undulating

18 - 30% moderately sloping to rolling

30 - 50% steep hills & mountainous

50% very steep hills & mountains


The surface and subsurface drainage patterns on a site greatly influence land use.

Important in developing a system for site drainage that makes use of existing watershed drainage patterns.

Existing water bodies – variation and purity

Natural and man-made drainage channels – flow capacity, purity

Surface drainage pattern – amount, directions blockages, flood zones, undrained depressions, areas of continuing erosion

Water table – elevation and fluctuations, springs, flow directions, presence of deep acquifers.

Water supply, location, quantity and quality.

River Basin

Indicates the area from which water is gathered to fill streams and rivers.

A project area near a stream is flood prone.

Flash floods can occur.

Necessary to determine the total surface drainage system and plot into the map the water catchment area that feeds any local surface water.


50-100 year storms be studied to see if all development should be excluded or if a land use such as a recreation may be located that would receive little damage by flooding.

In building adjacent to streams or rivers, detailed flood studies and special permits are necessary.


Water-bearing strata of rock, gravel, or sand in which groundwater is stored.

Very valuable resource of potable water and must be protected from pollution.

Acquifer recharge areas are the points where surface water meets or interchanges with an acquifer.


have very valuable natural functions and considered a protected area.

Areas that are covered by water or that have water-logged soils for long periods during the growing season.

Include shrub swamps, marshes, bogs, mangrove swamps, salt marshes, and similar areas.


Soil type and depth, value as an engineering material and as a plant medium, presence of hazardous chemicals or contaminants.

Areas of fill or ledge, liability to slides or subsidence, capability for mining.

Data in soil surveys are valuable in determining suitability for land uses.

Vegetation & Wildlife

Dominant plant and animal communities-their location and relative stability, self regulation, and vulnerability.

General pattern of plant cover, quality of wooded areas, wind firmness, regeneration potential.

Specimen trees-their location, spread, species, elevation at base, whether unique or endangered, support system needed.


Regional pattern of temperature, humidity, precipitation, sun angles, cloudiness, wind direction and speeds.

Location microclimates: warm and cool slopes, wind deflection and local breeze, shade, heat reflection and storage, plant indicators.

Ambient air quality, dust, smells, sound levels.

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