Modeling - Field Sampling: Principles and Practices in Environmental Analysis - page 174

model represent 10,000 cm in the real landscape. Using a scale model allows one to
calculate distances between features.
Such a scale model can be used to locate sample sites and monitoring wells. In
addition, underground features (e.g., pipelines, caves, buried tanks) can be represented in
such a way that samples can be taken so as not to disturb or interact with them. Note that
in a scale model the position (north, south, east, west) and depth of the features must be
exactly known for their correct placement in the model and subsequent avoidance.
Another use of such models would be for comparisons before and after. In this case
two or more models can be constructed showing the present situation and the situation as
it is envisioned during the project and when the project is completed. This will allow the
involved parties to envision the changes so that they will not be surprised by proposed
changes or by their effect on the environment.
7.1.2. Dynamic
A dynamic model may be constructed in a manner similar to a static model. In this case,
however, the model is interactive in that it shows the interaction between components in
the environment. For the environment this type of model often involves observing the
interaction between water and soil. It might also show the interaction between air and soil
or all three, however.
Many qualitative models of the interaction of soil and water are available. In Chapter 2
there is a model that illustrates the movement of water through soils with horizons having
different textures. Another model is to drop water on soil peds held on a wire screen. The
stability of the peds can be seen by how they hold up to running water. If water is
allowed to drop from some height onto soil it will be splashed. The drops dislodge soil
particles that are then carried out of the soil for some distance. Water falling just a few
meters can cause soil to splatter a meter or more from the point of impact. (See landscape
modeling in Section 7.4.)
If a board with ridges on three sides is constructed and filled with soil, it can be used to
model stream movement and development. (See Figure 7.1.) To protect the wood from
water, the board is often covered with plastic before the soil from the area being
investigated is added. The board is placed at an angle to represent the slope of the area
being investigated. A source of water is allowed to flow across the soil. As the water
moves across the soil it will form a “stream” that mimics the actual movement and action
of natural streams. In this way the possible movement of contamination in a field may be
estimated before the field is sampled. It will also show where field offices and storage
facilities are best located.
This type of model is also valuable in observing the effects of flooding on an area. The
amount of water flowing across an area can be doubled, tripled, or made 10 times larger,
and the effect of these changes noted. If the area is particularly prone to periodic flooding
this type of model can be invaluable in locating both sampling sites and sites for
buildings. This type of model is shown in Figure 7.1.
Blowing air across soil or sand when it is wet or dry will model what happens during
wind erosion. Such a model can be used to design barriers or other structures to prevent
or lessen wind erosion. This can thus help in understanding how to design a sampling