Runoff Characteristics of Thiaumont Platform

Introduction:

Often times the tools within a GIS are not autonomous. Such is the case when deriving runoff characteristics. In this post, I will provide my workflow in determining which locations within the cratered landscape receive the most surface runoff. This runoff model compliments Runge's energy model in explaining the relationship between the amount of moisture available for leaching and soil development.

Methods:

The process of developing a surface runoff and accumulation model consists of multiple steps. A clear and organized workflow model provides the most efficient means of communicating the process (model 1). Below the model is an explanation of each step. All tools used throughout this project may be found in the spatial analyst toolbox under hydrology and surface.



 

1) The model begins with adding a digital elevation model (DEM) to the project. My elevation model contained microtopographic relief ranging from 401 meters to 406 meters of the Thiaumont Platform, Verdun, France (figure 1).

Figure 1: Digital Elevation Model of Thiaumont Platform. The DEM provides all of the necessary elevation data for the entire process.

 

2) The flow direction tool is used with the DEM entity to determine the direction the water will travel across the surface (figure 2). This tool is essentially calculating the aspect, the maximum angle of downslope direction (ESRI).


Figure 2: Flow direction shows the downslope angle with the steepest gradient

3a) Once the flow direction has been determined a tool may be used to locate any sinks within the watershed and fill them. Depending on the application of the research, this tool may or may not be used. For example, when observing the watershed of a large area, you may want to exclude depressions that collect surface flow. For my application, each sink (crater) was the target of my study so this step was excluded.

3b) The flow accumulation tool is used to calculate areas with the highest rate of movement depending upon the flow direction layer (figure 3). This shows where surface runoff is most likely to occur and where it will accumulate.

Figure 3: Flow accumulation uses the flow direction to determine where water is most likely to flow across the surface.

4) After flow accumulation has been determined, the point pour tool is used to delineate the location of drainage basins (ESRI). The locations calculated in step 3b are used to determine where each microwatershed begins and ends (figure 4).


Figure 4: Pour Point uses the flow accumulation previously calculated to show drainage basins. A hillshade was applied to beter visualize the relationship between elevation and water accumulation.

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.


 Conclusion:

This exercise provided invaluable information for my studies on landscape evolution of Verdun. Using functions in hydrology allows me to better understand the processes at work forming the landscape. Next week I will explore the recovery of vegetation using the soil knowledge I gained during the past few weeks.



Catena Concept and how it relates to Verdun Craters

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.


Soil Genesis (Annotated References)

Pedology Context (Thiaumont)
    Clay Dominated
            Poorly Drained (low permeability)
    Formation
            Formed over shale and colluvial parent material
            Shallow bedrock
                     perched water tables
            
Soil Development Accelerant

Runge's energy model:  S = f(o,w.t)
Soil (S)
Intensity factor (w) (Water available for infiltration)
      Climate
           Duration and intensity of rainfall
      Relief
           Run-on/Runoff
                 Soil Permeability
           Organizing soil profiles (gravitational forces)
Organic Matter Production (o)
       Source of humus in soil (prevents weathering (melanization))
       Offsets w factor
Time (t)

Applicable to unconsolidated topsoil i.e. loess or till. Less applicable to coniferous forest

The Verdun landscape has a wide range of relief as a result of explosive munitions. This model will be helpful in explaining soil development within the cratered landscape.  Vegetative litter found at the bottom of the craters adds to the organic matter found within the soil (humus).  However, the dominant soil seen at Thiaumont Platform was clay rich, slowing the effectiveness of Runge's model. To be an effective accelerant of soil development, the environment must meet certain criteria. (1) The preexisting soils need to be permeable for a higher rate of water infiltration leading to horizonation (Schaetzl, Anderson, 2005)

Catena Concept
Soil transect running from the base to the top of a hill.
Provides informationon hillslope hydrology and shape, and stratigraphy.
Anthrosols (modified soils due to human activity)

Using ESRI Map Applications to Present Spatial Data

During this week, I explored the various ESRI Online map application templates trying to find the best one to present the data I collected in Verdun, France. Throughout the process I encountered a number of shortcomings that kept leading me back to the basic template design and, unfortunately for ESRI, sometimes Google Tour Builder.

The first map application template I used was the Elevations Profile. I figured this would be a creative way of presenting the landscape context of my data. Before using this template I had these expectations of its particular uses. I imagined being able to use my own DEM layer for my elevation data, and having scroll over effects to present various study sites. Once I began experimenting with the template, I realized it did not nearly meet my expectations. The interface provided is just terrible which I may extend to the ESRI story mapping creation process in general. Very simple tasks quickly become daunting, such as editing your map in general. Unlike the simple story map template, there doesn't seem to be any "builder mode" to edit and add features to the map. The only editing options I was able to find are located at the menu before actually opening the app. Once you get into this editing page, the purpose drop down menu located under Properties must be set to configurable (Figure 1).

Figure 1: To be able to edit an elevation profile template you have to select configurable under the application properties. Note the selection for an application programming interface. To utilize this web mapping application to its fullest extent, some background knowledge of JavaScript, Silverlight, or other API is needed.

Only after this is done can you actually begin creating a Elevation profile. This feature is cool and all, but is there an intuitive process that allows you to add your own data? The short answer is no, unless you have knowledge of JavaScript, Flex, Silverlight or another application programming interface. I have yet to figure out how to do even the basic task of saving the elevation profile to be viewed during later use.

I ran into the same problem when attempting to create a mapping application that incorporates a functioning slider. I figured this application would provide an interactive way of comparing my digital elevation model of the region, with aerial imagery. However, similar to the elevation profile template, some knowledge of an API is needed.

As a last resort I reverted back to the original story map template. Although this template doesn't provide the most functional method of presenting spatial data, the interface is very user friendly. To streamline the photo hosting and geocoding process, a .csv file was created with the server addresses to all of my images (Figure 2).

Figure 2: .CSV file with the photo addresses hosted by our GIS server.

 During this process, additional problems were encountered. To be recognized by ArcGIS Online, the format must exactly match their provided template. Null values, fields lacking any input, defeat the purpose of creating a .csv and all of the fields must include relavant information. It is important to note that Internet Explorer is not a recognized browser of the .csv file, for this reason Google Chrome was used