Rivers Fieldwork - Key words

Learn key words and definition

Accuracy

How close measurements are to the true value, such as the exact river depth or flow speed. Helped by using equipment such as a digital flow meter to record velocity, rather than a cork which might get caught on vegetation.

Precision

How consistent repeated measurements are, showing little variation. This helped by using equipment such as a caliper which measures to the nearest mm. 

Reliability

The ability to get the same results if the fieldwork is repeated under similar conditions, helped by repeating the data collection multiple times, removing anomalies and calculating the mean average.

Validity

How well the data and methods truly measure what they are supposed to in the river study. Helped by making sure the sites and methods are appropriate to your aims.

Stratified sampling

Selecting fieldwork sites based on distinct characteristics or location to ensure a good range of data and compare different areas downstream

Channel width

The distance from bank to bank at the surface of the water measured using 30m tape measure held tight

Channel depth

vertical distance from the water surface to the river bed, measured at equally spaced intervals across the channel using a 1 meter ruler. 

Velocity

Speed at which water flows downstream, measured by timing a floating object over a 10m strech or using a flow meter. 

Gradient

Slope or angle of the river channel bed, usually measured with a clinometer and ranging poles across a 10m stretch to determine how steep or gentle the stretch is.

Sediment size

Leng of the longest axis of a pebble or piece of sediment, measured with a calliper or ruler.

Sediment shape (Powers index)

The degree of roundness or angularity of river sediment, classified using a scale from 1 (angular) to 6(well-rounded)

Field sketch

An outline drawing of the river channel and landscape annotated with arrows

Primary data

Orignal data collected directly during fieldwork, such as widths, depths, and pebble sizes measued personally.

Secondary Data

Data sourced from elsewhere, like published river discharge data or GIS maps 

Mean

The average value, found by adding together all measurements and dividing by the number of readings. 

Range

The difference between the largest and smallest valyes in a data set

Mode

The most common value recorded in a data set

Line of best fit

A line drawn on a scatter graph to show the trend or correlation between two variables

Interpolation

Estimating a value within the range of your existing data points on a graph or table, such as using the best fit line on a scatter graph to estimate the velocity between 2 sites you visited

Extrapolation 

Estimating a value beyond the range of collected data, assuming existing trends continue.

Anomaly 

A data result that does not fit the general pattern, possibly due to operator/human error or unique conditions at one site