Runoff Results

The results of this activity provides spatial analysis of water movement and accumulation across a topographic surface. These tools effectively aid in the understanding of fluvial geography by providing spatial representations of where runoff is likely to occur and the location of the resulting drainage basins. Figure 5 shows a three dimensional representation of my study site including hydrologic characteristics that will help in my understanding of soil development under the Runge Energy Model and the Catena concept. According to this model (figure 5), soil development should be accelerated in locations labled as dark blue considering they are unsaturated (Runge). 

 

Figure 5: This three dimensional model provides a great spatial representation of the runoff characteristics of the Thiaumont Platform. The microrelief of the landscape adds to the variability in soil development in the area.

Catena Concept
There exists a relationship between soils on one part of the landscape and soils nearby. The Catena concept provides an excellent way of illustrating this geographic relationship using slope dynamics. The main components of a contena are (1) fluxes of water and matter, and (2) the location of the water table (Schaetzl, 2005). On a sloped surface, water infiltration rates depend upon the permeability of the soils and the gradient of the slope. If the slope gradient is high enough, sediments will be transported, and deposited in the form of alluvium and slopewash. The location of the water table determines how well these sediments are deposited, thus contributing to the development of the soils. 

According to the Runge Energy Model, the two most important variables for soil development are climate, and relief.  The relief of the landscape determines how the catena concept applies, and the water introduced into the system is dependant upon the climate. In artillery craters of Verdun, France both the Runge Model and the Catena Concept are used to explain soil formation in a way that promotes and/or inhibits the recovery of healthy vegetation. 

Much of the Verdun landscape is littered with craters caused by artillery fire during World War I. As a result, soil development changed in process following this initial disturbance. Soil profiles within cratered landscapes can be explained using the Runge model and the catena concept of soil development. 

Similar to the Jenny model, Runge's energy model explains soil development as a function of relief, climate, organic constituents, and time (Schaetzl, 2005). Climate and relief, being the most important factors, determine the amount of water accessible to the system and the potential energy of that water moving through the soil profile. Locations where water accumulates and permeates through the soil profile, will have better developed soils (Schaetzl, 2005). The use of Runge's energy model to explain soil development is limited by the permeability of the soil and the location of the water table. Locations with a low water table and soil textures that encourage leaching will have the most developed soil. Alongside water available for leaching is the important variable of relief. This concept is best explained using the Catena concept.

Figure 1: Pour Point analysis uses elevation data to model where water is likely to accumulate. Areas shown in light blue depict low elevations where soil moisture is highest. Using this data and the Catena concept, areas in light blue are likely to have more developed soil profiles and pronounced horizination.

Under the catena concept, soil development in areas with heavy relief depends upon the location of the water table and fluxes of water and matter within the soil profile (Schaetzl, 2005). In fully saturated crater bottoms (perched water table), soil development is slower than crater bottom well above the water table. Leached material through the soil profiles exacerbates horizonation and soil development (figure 2). As water is introduced into the soil profile, sediments are transported by colluviation and slopewash and deposited within crater bottoms (Schaetzl, 2005).  As a result, soils located within crater bottoms become more developed (Hupy, Schaetzl, 2008).



Figure 2: The catena concept explains soil development as a function of surface topography. On slope surfaces, soil development is not uniform. The movement of water through the soil profile allows for the transportation and deposition of sediments.

Microtopography, often overlooked, is a significant factor influencing soil development. Small changes in relief create pit-and-mound topography that affects variables contributing to soil development such as soil temperature, organic litter accumulation, and water infiltration/movement Schaetzl, 2005). A horizons within crater bottoms are expected to thicken as a result of the decomposition and weathering of organic materials. However, tree litter may impede the growth of vegetation as will erosive activity on crater sides.