PHYSICAL FIELDWORK – Rv Conway

What is the key question of the investigation on the Afon Conwy?

To investigate downstream change on the Afon Conwy.

What does the Bradshaw model illustrate?

• how the size affects stream flow

• river flows downsteam - tributaries feed more water → higher dishcarge

• increased volume of water → more power to vertical + laterally erode = increase in channel depth + width

What is the hypothesis about discharge on the Afon Conwy? and explain why

The discharge will increase with distance downstream due to tributaries joining the main channel.

• more tributaties - joined main channel + land will have been drained

Velocity (speed) will increase with increasing cross sectional area going downstream on river conway

• more water - added - channel becomes wider

• velocity increases - smaller proportion of the river water is in contact with the bed and banks → there is less friction

what are the hazards

• Slips, trips, and falls

• the water + falling into river

• poor weather - rain + wind

what is risk and prevention for slips, trips and falls

• Injury and break or sprain an ankle or wrist.

• Getting soaked if the fall is in the river

• and then suffering from cold (hypothermia)

• Reduce - Watch where you are placing your feet and using sensible footwear with

• good grips. Alerting other people if stones are slippery so they don't slip

How was width measured in the study?

By measuring from the left bank to the right bank using a tape measure along the water's surface.

how was depth measured

• taken at 5 locations across the width - divide width by 4

• meter ruler placed upright here

how was velocity measured

hydroprop was used to measure the flow at the same three locations as the depth

placed just below the surface with the propeller facing directly upstream.

What limitation was encountered when measuring depth in the river?

Large angular boulders blocked the river at certain locations.

What challenge were faced regarding the hydroprop?

Sometimes the river was too shallow for the hydroprop to function effectively due to lack of flow

limitation of measuring width

• difficult to keep the tape measure tight

• more accurate - more people in river

data

	site 1	site 2	site 3
width	0.53	1.85	2.5
depth	0.02	0.11	0.28
velocity	0.17	0.53	0.41

What is a challenge related to drawing cross-sections for data presentation?

It is hard to construct accurately without a computer and with inconsistent scales across sites.

what is stratified sampling

• divide into areas

• take a a proportional number of measurements in each area

• sample randomly or systematically within the area

stratified sampling - advantages + disadvantages

advantages

• all sections of the river will have will have been sampled,

• distinct differences across the study area

• divided into different areas e.g. upper, middle, lower

disadvatages

• not possible to safely measure width + depth of river in lower course

conclusion for river width

• Hypothesis – width should increase downstream

• Data supports

• Shown in bradshaw model

• due to lateral erosion → abrasion increasing → the river flows downstream → the increased energy from the additional water = joins the main channel from tributaries

conclusion for river depth

• hypothesis – depth will increase with distance downstream

• data supports

• shown in bradshaw model

• vertical erosion - abrasion

• increased energy from addtional water from tributaries

conclusion for river velocity

• hypothesis – velocity will increase with distance downstream

• supports – not a clear pattern due to anomaly – human error (used jenga blocks, change of method) but overall increases

• shown in bradshaw model

• reduced sediment size → less friction → more energy from attrition

• and increased volume of water from tributaries