What are the natural processes and assets in the watershed?

What are the natural processes and assets in the watershed?

Nature performs valuable work for humans without investment. Certain areas are not suitable for human habitation – hurricane paths, earthquake areas, floodplains, etc. Planning should make sure that people do not live in a floodplain, on a slide area, in an earthquake zone, hurricane path, fire-prone forest or mudslides. We need simple regulations that protect both the values of natural processes and of humans. The intrinsic value (value for themselves not for human use) of these processes can be preserved by designating them as open space which makes sure that they continue to provide vital natural processes and will leave these areas unharmed by often violent processes. This would ensure that development would happen in areas that are intrinsically suitable, which is where dangers were absent and natural processes unharmed.”

Water

“A single drop of water in the uplands of a watershed may appear and reappear as cloud, precipitation, surface water in creek and river, lake and pond or groundwater; it can participate in plant and animal metabolism, transpiration, condensation, decomposition, combustion, respiration and evaporation. This same drop of water may appear in water supply, flood, drought and erosion control, industry, commerce, agriculture, forestry, commerce, agriculture, snow, stream, river and sea. We conclude that nature is a single interacting system and that changes to any part well affect the operation of the whole.”

p. 56

“Terrestrial (land) processes require water and the freshwater processes are indissoluble from (part of) the land …. Therefore, land management will affect water and water management will affect land processes. Plans can be made for some aspects of water movement – precipitation and runoff, surface water in streams and rivers, marshes and floodplain, groundwater in aquifers and, lastly aquifer recharge, the most critical phase of water movement. Analyzing natural processes help to determine which land should stay in their natural condition, land that can tolerate certain uses but not others and land that is most tolerant to human habitation which is free from danger and does not harm other values.

Land can be categorized according to their value for natural processes and suitability for human habitation. Nature performs work for humans, often best done in the natural condition of the land, and certain areas are intrinsically suitable for certain uses while others are less so. We can rank eight natural processes in order of both value and intolerance to human use. When the order is reversed it then gives a hierarchy of suitability for human use.

What is the best way to live on the land?

Intrinsic suitability for human use	Natural process value and intolerance to human use
1 Flat land (except prime agricultural land)	1 Surface water
2 Forest, woodlands	2 Marshes
3 Steep slopes	3 Floodplains
4 Aquifers	4 Aquifer recharge areas
5 Aquifer recharge areas	5 Aquifers
6 Floodplains	6 Steep slopes
7 Marshes	7 Forests, woodlands
8 Surface water	8 Flat land

Surface Water-

In principle, only land uses that are inseparable from waterfront locations should occupy them; and even these should be limited to those which do not diminish the present or prospective value of surface water for supply, recreation or amenity.

Marshes-

In principle, land-use policy for marshes should reflect the roles of flood and water storage, wildlife habitat and fish spawning grounds. Land uses that do not diminish the operation of the primary roles include recreation, certain types of agriculture and isolated urban development.

Floodplain-

The 50-year or 2% probability floodplains being accepted as that area from which all development should be excluded save for functions which are unharmed by flooding or for uses that are inseparable from floodplains. In the former category fall agriculture, forestry, recreation, institutional open space and open space for housing.

Aquifers-

An aquifer is a water-bearing stratum of rock, gravel or sand, a definition so general as to encompass enormous sires of land. This valuable resource should not only be protected, but managed.

Land-use prescription is more difficult for aquifers than for any other category as these vary with respect to yield and quality. It is clear that agriculture, forestry, recreation and low-density development pose no danger to this resource but industry and urbanization in general do.

All prospective land uses should simply be examined against the degree to which they imperil the aquifer, those which do should be prohibited. It is important to recognize that aquifers may be managed effectively by the impoundment of rivers and streams that transect them.

Water for human use is often elaborately disinfected to be potable. In contrast to the prevailing view that one should select dirty water for human consumption and make it safe by superchlorination , it seem preferable to select pure water in the first place. Water is generally pure in aquifers and must be protected from the fate of many rivers.

Development that includes the disposal of toxic wastes, biological discharges or sewage should be prohibited. The use of injection wells, by which pollutants are disposed into aquifers, should be discontinued.

Development using sewers is clearly more satisfactory than septic tanks where aquifers can be contaminated, but it is well to recognize that even sewers leak significant quantities of material and are thus a hazard.

Aquifer Recharge Areas-

As the name implies, such areas are the points of interchange between surface water and aquifers. In any system there are likely to be critical interchanges. It is the movement of ground to surface water that contributes water to rivers an stream in periods of low flow. Obviously the point of interchange is also a location where the normally polluted rivers may contaminate the relatively clean-and in many cases, pure-water resources in aquifers. These points of interchange are then critical for the management and protection of groundwater resources. By the careful separation of polluted rivers fro the aquifer and by the impoundment of clean streams that transect it, the aquifer can be managed and recharged. My regulating land uses on these permeable surfaces that contribute to aquifer recharge, normal percolation will be allowed to continue.

Steep Lands-

Steep lands, and the ridges which they constitute, are central to the problem of flood control and erosion. Slopes in excel of 12 degrees are not recommended for cultivation by the Soil Conservation Servnce in the US. The same source suggests that, for reason of erosion, these lands are unsuitable for development. The recommendations of the Soil Conservation Service are that steep slopes should be in forest and that their cultivation be abandoned. The role of erosion control and diminution of the velocity of runoff is the principal problem here. Land uses compatible with this role would be mainly forestry and recreation, with low-density housing permitted on occasion.

Prince Agricultural Land-

Prime agricultural soils represent the highest level of agricultural productivity, they are uniquely suitable for intensive cultivation with no conservation hazards. It is extremely difficult to defend agricultural land when their cash value can be multiplied tenfold by employment for relatively cheap housing. Yet the farm is the basic factory –the farmer is the country’s best landscape gardener and maintenance work force, the custodian of much scenic beauty. Mere market values of farmlands do not reflect the long-term value or the irreplaceable nature of these living soils. An omnibus protection of all farmland is difficult to defend; but protection of the best soil in a metropolitan area would appear not only defensible, but clearly desirable.

The farmer, displaced from excellent soils by urbanization, often moves to another site on inferior soils. Excellent soils lot to agriculture for building can finally only be replaced by bringing inferior soils into production. This requires capital investment. “Land that is not considered cropland today will become cropland tomorrow, but at the price of much investment.” Prime agricultural soils are limited in area. Therefore, given a choice, prime soils should not be developed.

Forests and Woodlands-

The natural vegetative cover for most of this region is forest. Where present, it improves microclimate and it exercises a major balancing effect upon the water regime –diminishing erosion, sedimentation flood and drought. The scenic role of woodlands is apparent, as is their provision of a habitat for game; their recreational potential is among the highest of all categories. In addition, the forest is a low-maintenance, self-perpetuating landscape. 

Forests can be employed for timber production, water management, wildlife habitats, as airsheds, recreation or for any combination of these uses. In additions, they can absorb development in concentrations to be determined by the demands of the natural process they are required to satisfy.  

Here are some examples of

1. Natural processes that perform work for humans

• natural water purification
• atmospheric pollution dispersal
• climatic amelioration
• water storage
• flood, Drought and erosion control
• topsoil accumulation,
• forest and wildlife inventory increase

2. Offer protection or are hostile, dangerous

• estuarine marshes
• floodplains

3. Unique or especially precious

• geological, ecological or  historic interest

4. Vulnerable

• beach dunes
• spawning and breeding grounds
• water catchment areas

Paraphrased and quoted from Ian McHarg,  Design with Nature p. 58-61