Rivers Fieldwork

Title

To investigate dowunstream changes on the river Tillingbourne

Why was you location, river Tillingbourne, chosen?

• There was a river which had different landforms which were accessible (1) which meant that I could compare characteristics (1).

• We selected three sites along the river (1) that were in walking distance (1) as this allowed us time to collect the data one day (1).

Systematic Sampling

ccollecting data in an ordered or regular way. (1)

students could pick the first site at random then pick subsequent sites at a set defined distance (1) this would help ensure that the sampling covered a whole range of changes along the river channel (1)

Poor representation of overall investigation, time constraints, can be biased, can be under representative, unreliable, inaccurate

Risk and Prevention

hypothermia → wear lots of layers to keep warm

Primary Quantitive Data Collection Methods

• Velocity with Cork or Float

• Width

• Depth

Velocity with Cork or Float

• Method: use tape measure to measure 3m along, place cork 50cm upstream of start of tape measure, use stopwatch to time how long it takes cork to travel 3m, measure at regular intervals, record the results, used to create a graph

• Justification: collect quantitative data on velocity and specific distance of river to calculate discharge

• Limitation: cork stuck as it flowed down river, slowed cork down, use hydroprop

Width

• Method: choose representative location on river, measure river from bank to bankk, measure at regular intervals, record the results, used to create a graph

• Justification: find cross-sectional area of river by transferring data to graph paper → accurate, necessary to calculate discharge

• Limitation: tape measure not straight 91) this will have increased the number on the ruler (1) leading to the incorrect width being recorded (1), ensure tape measure is pulled as straight and tight as possible

Depth

• Method: tape measure is stretched across the river (1) measure the depth of the water at 25 cm intervals (1) using a meter rule and then record the results, used to create a graph (1)

• Justification: create a cross-section to see how the channel shape changes and allow greater representation of the river, needed for discharge

• Limitation: student may not have held the ruler perfectly vertical (1) this will have increased the number on the ruler (1) leading to the incorrect depth being recorded (1), use set square

How to measure gradient?

• use clinometer

How to measure sediment size?

• measuring pebbles at different points along river

• Power’s Roundness Scale → identify shape of sediment

How to measure river wetted perimeter?

Measuring tape (1)

Rope / weighted chain (1)

How to increase reliability of primary quantitive measurements?

students can take more measurements, compare results to another group, or ensure one person in the group is responsible for measurements

Primary Qualitative Collection Methods

• Field Sketch

• Photographs

• Questionnaire

Field Sketch

• Justification: records main features of river profile at different sites (1), help students indentify differences (1), students can get quick view of area as working, support recall later

• Disadvantage: different perceptions, may over-exaggerate features, quick sketch means key features not recorded, inaccuracies later on (spend more time making detailed sketch with labels)

Photographs

• Justification: objective (reliable, accurate), annotations highlight key features of river profile at different sites

• Disadvantage: subjective, bias (consistent compass direction), small area, single moment in time (photos at regular intervals)

How to carry out questionaire

Ask public questions about the river (1), could by interview or questionnaire regarding flooding/litter/ pollution etc. (1).

Secondary Data

• GIS Topographic Map

• Justification: plan fieldwork so suitable data can be collected, compare with primary data

• Limitation: could be innaccurate/ bias, from different location or not collected over same time period

Presenting Fieldwork

• Cross-profile graph

• Line Graph

• Scatter Graph

• Bar Graph

Cross-Profile Graph

• width and depth

• Advantages: easily compare across different sites (1) and recognise any differences (1) easy to construct (1) using Excel to spot anomalies in data (1)

• Disadvantages: time-consuming to collect enough data for accurate profile, only shows shape at specific points

Line Graph

• velocity

• Advantages: allows patterns to be easily visualies and understood, easy comparison with other sites to check if they fit with hypothesis or easy spotting of connections to identify anomalies

• Disadvantages: joining points with lines suggests continous change even though flunctuates, only shows changes between points measured, small variations in velocity misses

Scatter Graph

• Velocity

• Advantage: analyse data for any correlations (1), identify anomalies (1), allowed to see correlation between factors, to produce clear conclusion

• Disadvantage: points can overlap and become difficult to interpret, anomalies make relationship appear weaker or misleading

Bar Graph

• Velocity

• Advantages: easy to compare river velocity at different sites, to produce clear conclusion, clear and simple to draw and interpret, suitable for discrete data collected at separate locations

• Disadvantages: does not show continous changes in velocity along river, oversimplify differences between sites, less effective for showing trends or connections and identifying anomalies

Data Analysis

• mean → smooth out variations in daya, adding up each reading and divide by number of times data recorded (3)

• percentage → relative → differents sets of data can be comapred (3)

• interquartile range → remove outliers in data, caused by human error in data collection (3)

• line of best fit - shows overall trend in scatter graph, helps identify positive negative or no correlation

Accuracy and Reliability

Accuracy is about making judgements about how close conclusions are to the actual changes occurring in the river environment where the fieldwork was carried out.

Reliability is about how dependable the data is and often relates to having a big enough sample size to reach a conclusion.