The aim of the field trip was to study the changing characteristics of a river as it travels downstream, and to obtain “primary data” to answer hypothesis questions (see page ). We collected primary data by visiting Lower Debden Brook, Upper Debden Brook Upper and the River Roding, which form the River Roding drainage basin. Measurements were taken and carefully recorded at each study site.
To investigate the aim, it was broken down into eight hypothesis that were tested (see page)
The trip to Epping Forest was worthwhile because I gained geographical knowledge on the topic of “Rivers” and discovered why river characteristics change as you travel downstream. I learnt that at the source of the stream the river’s energy is focussed downwards which creates vertical erosion. This type of erosion causes the channel to become deep and narrow. Further drownstream, due to the formation of meanders, the rivers energy is focussed outwards in the form of lateral erosion.
This occurs on the outside of the bends. At different stages of a river there are various processes which produce different landforms For example, v-shaped valleys in highland regions and deltas in lowland regions. Knowing this information enables me to understand the hypothesis because each statement involves vertical and lateral erosion in explaining why each characteristic occurs. For example the wetted perimeter (see page ) is the amount of riverbed that is submerged by water. This measurement depends on the width of the channel and this changes due to vertical and lateral erosion. Another example is stream velocity (see page ) Water flows faster through smaller spaces, therefore, because vertical erosion narrows the channel and lateral erosion widens the channel the water flows at different speeds.
Although the field trip was fairly successful there were many limitations. These included:
* the study sites were all within the same drainage basin
* the different sites were only visited once, on one day, and in one season
* the equipment used to take the measurements was very basic and did not enable us to gain precise results. Also, we had no experience of using the Gun Climonetre, which was used to measure the gradient. Therefore the results could not be relied on as being accurate.
The method we followed allowed us to obtain some inaccurate results. For example measuring the float time (see page ). The cork was dropped into the river at point A and the time it took to travel to point B was recorded. If on the third run the cork became caught between dead branches, the time would obviously be slower than if it passed straight through. Under normal investigation conditions the odd result would be discarded but because we were restricted to the amount of time we could spend at each site we were unable to repeat the experiment and the inaccurate result used to calculate an average time.
To improve the work further I would repeat the measurements taken using the following changes:
* Allow more time to undertake the investigation
* Visit more than one drainage basin
* Because river characteristics change at different times of the year, the sites would need to be visited during different weather conditions.
* Use more modern equipment
* The methods used at each site would ideally be repeated at least 50 times and if possible 100 times in order to gain the most accurate results.