Sam Ballantine U21126: Geographical Enquiry and Field Research 07/03/14
Abstract:
For this executive summery I will be discussing my findings of my research that I carried out as part of a group project in Almeria region of South East Spain.
Our primary research proposal was to evaluate which type of Particle sampling technique was the most effective to collect data on particle sizes in
Ephemeral, gravel bedded streams. Our research consisted on testing several sampling techniques that included techniques proposed by Bunte & Abt
(2001)- namely the Heel-to-toe, Stratified Grid Sampling, Plum bob and a
Photographic sampling methods.
Section 1: Our Hypothesis.
I will be stating and explaining my Hypothesis that we created in order to commence our research in Almeria. The research question that we created we chose from Bunte & Abt’s article on sampling. Therefore the proposed research question became ‘Which Method of Sampling is the most Accurate in Identifying the Friction Factor of Gravel Bedded Ephemeral Streams, and how Sensitive is this measurement when used with the Darcy-Weisbach equation. We decided that finding out which type of sampling method would be the most appropriate for finding the friction factor- which is a critical part of the Darcy-Weisbach equation for finding out River Discharge levels.
Section 2: Introduction and justification.
Our study area took place in the Almeria region of South East Spain, more specifically in the Carboneras region of
Almeria. Our research was based within the various gravel bedded ephemeral streams located within the region, with our research sites being located at several key chosen areas along the
River Alias.
Figure 1 shows the catchment and drainage areas of the Almeria region.
The river system that we were researching in is highlighted within the red box that shows the catchment area of the River Alias. Additionally, the
Fig.1 Research area in Red Box (Maher et. Al 2007)
Almeria Region of Spain is classified as a
Drylands area, which can be defined as an area where potential evapotranspiration is greater than rainfall. This fact is greatly related to our research as the area has very little levels of rainfall per annum which has the effect that for a the large majority of the year rivers and streams run dry- allowing locals to use ephemeral river beds as transport and hiking routes. Data collected from the MET Office for the oxford region show that
Oxford receives an average of 659mm of rainfall per annum, whist the data

Sam Ballantine U21126: Geographical Enquiry and Field Research 07/03/14 collected from the Agencia Estatal de Meterologia (Almeria’s MET office equivalent) show that the region only receives an average of 196mm of rainfall per year.
Fig.2 Graph showing Monthly rainfall averages in Oxford and Almeria
However- these figures may be skewed as a result of a lack of equipment or highly distorted rainfall patterns in the region. Our justification for committing to our research is that understanding the area’s hydrology is critical to the survival of the people who live in these dry land areas.
Section 3: Our Method
This section of my executive summery I will be describing the research methods that we employed during our field research. We chose four particle sampling techniques that we took from Bunte & Abt’s paper- The Heel-to-toe method, the
Plum bob method, Stratified Grid sampling and Photo analysis. We chose these four methods so we could compare each to the other in several main criteria.
These included the times taken to perform each technique, the repeatability of each technique and the statistical variance that each technique yielded.
The first technique that we carried out at each site was the Heel-to-toe method.
This method involved the operator moving along the chosen transect, moving up the transect by placing one foot in front of the other. The operator would then proceed to bend over while looking at a fixed-point ahead-. While bending over, the operator would take a particle from those located at the toes of the forward foot. This would continue until a sample size large enough to represent the overall population was reached.
The second method we used was the Plum bob sampling- this would involve the operator using a nail tied to a piece of string and moving along their transect at agreed distances. The user would then lower the plum bob down at the point along the measuring tape towards the ground. The user selects the surface particle that the finest point of the plum bob hits. This process continues along the total length of the transect.
The third method we used was the Random Stratified Grid sampling technique.
This involves the use of a random number generator either from the Internet, or for our uses, the random number generator in Excel. The user would select two

Sam Ballantine U21126: Geographical Enquiry and Field Research 07/03/14 sets of random number pairs for use in selecting at which point to put the grid down, and the second to use as co-ordinates for sampling within the grid itself.
The grid was set up using a 20x20cm square, with handheld measuring tapes to donate the X and Y-axis. Samples were then taken from the second set of random numbers and taken from the closest values on the grid.
Our final technique we used to sample our particles was the Photographic sampling technique. The user would take top down photographs of the measuring tape at fixed heights and magnification. The photographs would have to include the measuring tape and the particles to be sampled from.
Section 4: Our Results
As a result of having chosen many different techniques to test against the criteria they were given, our results showed a very mixed set of results. Each technique was tested upon the time taken in the field, the repeatability and the statistical variance of their respective results. Firstly the results for the time taken in the field show a fairly standard set of results (see figure 3). The majority of the sampling techniques we used fell within 5 to 15 minutes, depending on the transect length and particle type. However the two anomalies were the Plum bob method and the photgraphic method. Using this information, we could then work out the repeatability of each technique. The photographic method was the technique which would be easily reapeatable, regardless of user as the photos are taken at set magnification and heights which allows for any user to set up repeats quickly. The second most repeatable would be the heel-to-toe method as the
Fig.3 Graph showing comparison of Time taken
Fig.6 Graph Comparing the times taken to perform each technique method is very easy to repeat from one user to the next and that it doesn’t take too much time to complete. Thirdly the plum bob method, whilst it takes along time in the field to do, the method remains the same each time, allowing it to be repeated by other users.
Looking at figure 4 we can see the
Fig. 4 Graph Comparing the Discharge rates given from each technique
Discharge rates that each sampling technique gave. Here, we can see that for each research site. The Plum bob and
Heel-to-toe methods gave very similar results, whereas the Grid and
Photographic methods give us wildly different results for each site.
Section 5: My Discussion
With the evidence provided from my figures and write up, the data provided us with a rich source of possible statistical tests to choose from. Considering that we were comparing four main particle sampling techniques, we chose the Anova

Sam Ballantine U21126: Geographical Enquiry and Field Research 07/03/14 test- or Analysis of Variance. We chose this test as it allowed us to test more than two data sets against each other, unlike the T-test.
One problem that each of the groups conducting fieldwork encountered was that we found that it was difficult to determine where the true bank of the river was.
This was due to the fact that since the riverbed was dry- and that it probably would have been dry for an exceptional amount of time (being an ephemeral stream), and at some research sites the riverbed had several smaller streams within the main channel. Once we agreed upon the river’s true bank we attempted to apply the same way in choosing the bank to other sites, as differences in this part of the survey would greatly affect our results due to it changing the wetted perimeter and therefore our Trapezoid. This would then affect our area of the river. This single aspect of the river sampling would greatly affect our results- as Discharge is calculated by multiplying Velocity by Area.
Looking at figure 8, we can see that the particle size data fully affects the overall
Discharge rates, therefore- the results that we gained from conducting our research is critical towards the final Q=VA equation.
In addition, the photographic sampling method results section I would avoid using, as we had to use an image analysis software called imageJ, this program was difficult to use and not specialized enough to perform our particle analysis.
In conclusion, considering the factors that lead us to conduct the sampling techniques that we chose, and the results from both the statistical tests and the tests upon the techniques themselves. I can state that our research was a success, and can be of use to others wanting to conduct similar research in gravel bedded ephemeral streams. The tests I would recommend to use would be the Heel-totoe method and the Plum bob method as the results from these tests appear to give us the most reliable results, followed by the Random stratified grid sampling and lastly the photographic sampling method.
Word count: 1546
References:
⦿ Bunte, K. & Abt, S. R. (2001). Sampling surface and subsurface particle size distributions in wadable gravel and cobble-bed streams for analyses in
sediment transport, hydraulics and streambed monitoring. United States
Department of Agriculture.
⦿ Colebrook, C. F. & White, C. M. (1937). Experiments with fluid friction in roughened pipes. Proceedings of the Royal Society of London. Series A,
Mathematical and Physical Sciences, 161 (906), pp.367-381.
⦿ Hey, R. D. (1979). Flow resistance in gravel-bed rivers. Proceedings of the
American Society of Civil Engineers, Journal of the Hydraulics Division, 105-
1: 365-379.
⦿ White, K. (1995). Field techniques for estimating downstream changes in discharge of gravel-bedded ephemeral streams: a case study in southern
Tunisia. Journal of Arid Environments, 30, pp.283-296

Sam Ballantine U21126: Geographical Enquiry and Field Research 07/03/14
⦿ No Author. (2014), Oxford Climate Data, Met Office, Retrieved on
16/02/2014 from: http://www.metoffice.gov.uk/public/weather/climate/oxfordoxfordshire#?tab=climateTables
⦿ No Author. (2014), Valores climatológicos normales: Almería Aeropuerto,
Agencia Estatal de Meterologia, Retrieved on 16/02/2014 from: http://www.aemet.es/es/serviciosclimaticos/datosclimatologicos/valore sclimatologicos?l=6325O&k=and
⦿ Maher, E., Harvey, A.M., & France, D. (2007), The impact of a major
Quaternary river capture on the alluvial sediments of a beheaded river system, the Rio Alias SE Spain, Geomorphology, Vol. 84, pp.334-356.