Accessibility Solutions for Diagrams and Other Visuals

Below are solutions to a couple of issues that frequently come up when using Canvas pages.

  1. You have an image you feel is particularly well-suited to conveying a concept but you realize that it would not be accessible to students with visual impairments. In this case, you could choose to write really lengthy alternative text describing the image. However, a better solution would be to describe the relevant information in the text. (See solution 1 below.)
  2. You have information that is lengthy and complex but it is important for the students to understand. You don't want to just give them a document but you also don't want to rebuild what you have in document form in Canvas. The solution is to provide some overview on the Canvas page and then link to more complex or multi-page information. (See solution 2 below.)

 

1: SOLUTION FOR  IMAGES THAT CONVEY INFORMATION

We can see on the Learning Pyramid diagram below that retention rates increase as the teaching methods become less passive. Average retention rates for lecture are 5%; for reading they are 10%; for audio-visual, 20%; and demonstration, 30%. However, once we move into participatory teaching methods they climb steadily from 50% for group discussion, 75% for practice and 90% for teaching others.

Learning Pyramid diagram

 

2: SOLUTION FOR MATERIAL THAT IS TOO LONG OR COMPLEX FOR A CANVAS PAGE

 

Unconfined Aquifer diagram

It’s critical to understand that groundwater does not flow in underground streams, nor does it form underground lakes. With the exception of karst areas, with caves in limestone, groundwater flows very slowly through granular sediments, or through solid rock that has fractures in it. Flow velocities of several centimetres per day are possible in significantly permeable sediments with significant hydraulic gradients. But in many cases, permeabilities are lower than the ones we have talked about, and in many areas, gradients are much lower. It is not uncommon for groundwater to flow at velocities of a few millimetres to a few centimetres per year.

As already noted, groundwater does not flow in straight lines. It flows from areas of higher hydraulic head to areas of lower hydraulic head, and this means that it can flow “uphill” in many situations. This is illustrated in the figure above. The dashed orange lines are equipotential, meaning lines of equal pressure. The blue lines are the predicted groundwater flow paths. The dashed lines red lines are no-flow boundaries, meaning that water cannot flow across these lines. That’s not because there is something there to stop it, but because there’s no pressure gradient that will cause water to flow in that direction.

Flow Nets

A flow net is a graphical solution to the equations of steady groundwater flow. A flow net consists of two sets of lines which must always be orthogonal (perpendicular to each other): flow lines, which show the direction of groundwater flow, and equipotentials (lines of constant head), which show the distribution of potential energy. Flow nets are usually constructed through trial-and-error sketching.

Read the following two handouts for constructing a flow net: