Soil And Water

Soils: Significance • • • •

Support Structural Loads Costs of Excavation Flow of water--Freeze/Percolation Provide nourishment and supportive environment for plants.

What is soil? • • • • •

The pulverized mantle formed from rock and plant remains by the action of weather and organisms. Soil is not static, but is continually developing and wasting. Beneath the organic litter, or surface of decomposing material, it is divided into conventional layers. 1st--topsoil a mixture of mineral and organic components, some of whose minerals have leached down to lowers levels. The topsoil has organic functions. Then--soil, largely mineral and is below most plant roots, but has some organic function. Finally--fractured and weathered parent material of the soil above, which has little or no biological activity and lies directly over bedrock.

Classification of soil Soil classified by particle size--from visible stones to fine invisible grains.Soils are extremely variable mixtures of these particles, and these variable mixtures have many distinct implications for site development. Two different classifications: • •

soils for agricultural purposes soils useful in construction of foundations and roads, (engineering classification)

An engineering classification refers to the exact composition of a particular soil body, wherever it occurs, as determined by laboratory tests or field specimens. Knowledge of the classification allows accurate predictions of bearing capacity or optimum percentage of some additive that will improve soil's performance for some engineering use.For light structures, field identification is sometimes all that is needed. There are ten broad classes of soil that can be identified in the field. These act very differently under loads or in the presence of water. Soil Classifications (abbreviated) Gravel: Particles over 2mm. in diameter Sand: 0.05 to 2mm. Gritty feel. Finest visible to the eye. Silt: 0.002-0.05mm. Grains invisible but can be felt. Smooth not gritty Clay: under 0.002 mm. Smooth and flowing, or in stiff lumps when dry. Plastic and sticky when

Soil Capabilities Crucial factors establishing soil distinctions and values: • • • •

Whether gravel, sand, silt or clay predominates. Whether mix is well or poorly graded. The liquid limit. The presence of organic matter.

Topsoil is always valued, and if stripped during construction, it is stored, if possible, for use onsite at the conclusion of the project. However, for engineering purposes, topsoil is usually disregarded. Bearing Capacity. Size of load, usually expressed as pounds per square foot (lb./sq.ft.), which a soil is able to support. Bedrock. The solid rock underlying unconsolidated surface materials (as soil). Erodability. Soil erosion and sedimentation control plans are required by many communities. Indicates temporary control measures and permanent ones--straw or jute barriers. Frost Action. Water residing in the soil can become frozen to depths of several feet, depending upon local winter conditions. Ice expands on freezing, heaving soil and causing displacement of building materials. Footings must extend to a depth below frost depth. Varies with location. Hard, sound rock has highest bearing capacity.If bearing capacity can't support proposed load or structure, soil can be removed and replaced with suitable material or other engineering measures-piles, spread footings, floating slabs, etc.--may be taken. Permeability. refers to ease with which water can flow through soil or any other material. Affects the design of a storm drain system. Where there is high permeability and the infiltration capacity of a soil is sufficient, water easily penetrates and is distributed in the natural water network below. Storm runoff is low, unless soil is saturated. Ecologically beneficial. Soil permeability affects dewatering excavation during construction. Saturated and organic soils exhibit the lowest. Shear Strength. Determines the stability of a soil and its ability to resist failure under loading. A result of internal friction and cohesion. Internal friction is the resistance to sliding between soil particles. Cohesion is the mutual attraction between particles which is due to moisture content and molecular forces. Sand and gravel: cohesionless. Clay: high cohesion--little internal friction. Water • • • •

Most important subsurface variable of all is the presence or absence of water: the moisture content of the soil. its internal and surface drainage. water table location.

Water Table. • • • • •

That underground surface below which the interstices of the soil grains are filled with water. Normally, this is a sloping, flowing surface which roughly follows the ground surface above and intersects with the ground at ponds, streams, lakes, "seeps" or springs. Its depth can vary remarkably, fluctuate seasonally or over long periods. A fluctuating water table will cause a heavy clay soil alternatively to shrink and to swell, disturbing foundations, just as a periodic frost will do. High water table makes for difficulties in excavation, as well as causing flooded basements, utilities and unstable foundations.

Look for : • • • •

Levels in existing wells. A mottled soil. Presence of water loving plants (alders, willows, etc.). Or test pit in wet season.

Subsurface Conditions: Summary of Danger Points. • • • • •

A high or fluctuating water table. The presence of peat or other organic soils, or of soft plastic clay, loose silt or fine waterbearing sand. Rock close to the surface. New, unconsolidated fill or land previously used as a dump, especially if toxic. Any evidence of flood, slides or subsidence.

The Systematic site Inventory General Site Context • • • •

Geographic location, adjacent land use patterns, architectural and urban form, access system, nearby destinations and facilities, stability or change in development pattern. Political jurisdiction, social structure of the locality, population change in surrounding areas. Ecological and hydrographic system of the region. Nature of the area economy, other proposals or projects nearby and their effects on the site.

Topography • •

Contours Pattern of land forms, typology, slopes, circulation possibilities, access points, barriers, visibility

Soils • • •

Underlying geology, rock character and depth, fault lines Soil types 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.

Water • • • • •

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 fluctuation, springs, flow directions, presence of deep aquifers. Water supply--location, quantity and quality.

Ecology • • •

Dominant plant and animal communities--their location and relative stability, selfregulation, 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.

Climate • • • •

Regional pattern of temperature, humidity, precipitation, sun angles, cloudiness, wind direction and speeds. Local microclimates: warm and cool slopes, wind deflection and local breeze, air drainage, shade, heat reflection and storage, plant indicators. Snowfall and snow drifting patterns. Ambient air quality, dust, smells, sound levels

Sensory Qualities • • •

Character and relationship of visual spaces and sequences. Viewpoints, vistas, focal points. Quality and variation of light, sound, smell.

Man-Made Structures • • •

Existing buildings: location, outline, floor elevations, type, condition, current use. Networks: roads, paths, rails, transit lines, sewers, water lines, gas, electricity, telephone, steam--their location, elevations, capacity, condition. Fences, walls, decks, other human modification to the landscape

Microclimate and its effects Loosely defined as the detailed modification of the general climate which is brought about by unique characteristics of topography, cover, ground surface and structural form. Factors that make the microclimate deviate from the macroclimate: Elevation above sea level

The steeper the slope of the land the faster the temperature will drop with an increase in elevation. 3.6 deg./1000 ft.

Form of the land South facing slopes are warmer than north facing. West facing slopes are warmer than slopes, because the period of high solar radiation corresponds with the high ambient air temperature of the afternoon. Low areas tend to collect pools of cold heavy air. Size, shape and proximity of bodies of water Alternating sea and land breezes, and increased humidity. Soil types Heat capacity, color and water content can have significant effect on the microclimate. Light colored sand can reflect large amounts of sunlight, which thereby reduces the heating of the soil, and thus the air, but at the same time greatly increases the radiation load on people or buildings. Because of their heat capacity, rocks can absorb heat during the day and then release it again at night. Vegetation By means of shading and transpiration plants can significantly reduce air and ground temperatures. Also can increase humidity. In a hot and humid climate, the ideal situation is to have a high canopy of trees for shade, but no low plants that could block the breeze. Vegetation can also reduce the cooling effect of the wind. Vegetation can also reduce noise and clean the air of dust and certain other pollutants. Man-made structures Buildings, streets and parking lots, because of number and size, have a very significant effect on the microclimate. Contours and Grading

Contours The contour line is a graphic technique used to illustrate the topographic qualities of the land.All points on a given contour line are at the same elevation--at or above (rarely below) sea level, the usual fixed or datum elevation.Dashed lines indicate existing conditions.On a concave slope the contours are shown spaced at increasing intervals with the lower contour lines spaced further apart than the higher ones. Valleys are indicated by contours pointing uphill. In crossing a valley, contour lines run up the valley on one side, turn and cross the stream, and run back the other side.

By convention, contours are labeled on the high side. Every fifth or tenth contour line should be drawn with a heavy line to simplify reading. Every contour closes on itself somewhere, either within or beyond the limits of the map. A contour that closes on itself within the limits of the drawing is either a summit or a depression. Depressions and summits are usually indicated by a spot elevation at the lowest point or highest point. On a convex slope, contours are shown spaced at increasing intervals going up a hill; the higher contours are spaced farther apart than the lower contours.

Grading At times, grading to obtain a desired Finish Floor (Fin. Fl.) elevation requires cutting into and filling of surrounding ground planes. This method of balancing the volume of material cut away with an equal amount filled in is both visually satisfying and economically practical. Planting Design The types of plants that we choose and how we arrange them in our gardens must satisfy functional and program needs, as well as to be able to fulfill our design intent. The ultimate goal of combining plants in the garden successfully is being able to achieve harmony. Plants should harmonize with the unique qualities of the site, building elements and materials, and other plants in a way that complement each other. A good planting design should appear as if each plant belongs there and not more can be added or taken away. Functions of plant materials • • • • • •

Aesthetics Environmental modification Screenings Circulation control Production Bio engineering

Forms of plant materials • • • • •

Trees Shrubs Ground cover Climbers and creepers Lawn

Use of plant materials as design elements: Plants can perform the same functions as constructed materials. •

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Evergreen hedges form walls, Arching tree limbs and sky become ceilings, Ground covers and lawns are floors, Low shrubs can act as windows or implied barriers, And tree alleys are corridors.

Plant Varieties: Every plant variety has a certain mature height, spread, form and ornamental qualities. A thorough understanding of the plant's character should be learned before becoming a choice in planting design. For the purpose of defining spaces in a planting design, we categorize plants by height. • There are canopy trees (trees greater than 60 feet in height), • upper under story trees (40'-60'), • lower under story trees (20'-40'), • large shrubs (15'-20'), mid-size shrubs (8'-15'), low shrubs (4'-6'), and • miniature shrubs and groundcovers (6"-4'), and • Herbaceous plants (plants that die back completely to the ground each winter). Functional Uses of Plants • • •

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Evergreen hedges can screen unsightly views, fibrous-rooted plants such as willow and bamboo can solve erosion problems on eroded slopes, Deciduous trees planted along southern and western aspects of a house can provide shade It is important to remember that plants solve many environmental problems. Plants help clean the air through their leaves (important in urban areas), retain moisture in the soil, reduce water runoff, And provide habitats for birds, insects and other animals. They can affect the microclimate of a place.

Preparation of maps • Site inventory and analysis maps present data in a format that can be easily viewed and studied. • The maps are created from site visits, photo documentation, historical research, and the analysis of both on-and off-site features. • The purpose of the maps is to identify environmental, physical and social conditions that could be affected by proposed development. • The final maps provide critical insight into the site’s character, the surrounding area, interrelationships between land features and land uses, and the social context of a site. Individual map can be designed to facilitate an analysis of the site through what is known as map overlay, or a composite analysis. Each layer (or group of related information layers) is placed on the map in such a way as to facilitate comparison and contrast with other layers. A composite layer is often developed to show all the layers at the same time this composite layer can be a useful tool for defining the best buildable areas and delineating and preserving natural feature conservation areas.