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Quiz & test questions Grade 6 Engineering & Design

Design Review of the Hearnside Dam Spillway Plan

A 20-point grade 6 review in which students check a fictional spillway plan against a flood rule and a freeboard rule, then evaluate a wider replacement design.

Objectives

  1. Students will evaluate the flow expression Q equals A times V for a rectangular spillway channel.
  2. Students will test a proposed design against a stated flood rule and a stated freeboard rule.
  3. Students will compare two channel designs and recommend one with reasons.

Vocabulary

Spillway
A dam's overflow channel, giving extra water a safe path around or over the dam when the reservoir gets too full. It protects the dam from being damaged in floods.

Also: freeboard, design flood, channel, velocity

Teacher overview

This 20-point assessment asks students to act as a review panel for a proposed spillway, the channel that carries flood water safely past a dam. The ten items mix two multiple-choice questions, six computation items, and two short-answer items, and they build toward a single judgment about whether the plan should be approved as drawn. The misconception the panel format exposes is that a design either works or does not: here the first plan passes the flood test and fails the freeboard test, so students must hold two separate rules in mind at once rather than settling for one verdict.

Design Review of the Hearnside Dam Spillway Plan — Grade 6 Engineering & Design
Name: ____________________________ Date: ______________

Assessment

Hearnside Dam, in the fictional village of Verrill

Every number below was invented for this review. Use only the numbers given in each item.

  1. (2 points) What is the job of a spillway?
    A. to store the village's drinking water
    B. to carry flood water safely past the dam
    C. to turn a turbine and make electricity
    D. to hold sediment out of the lake
  2. (2 points) The proposed spillway channel is 8 feet wide, and at the design flood the water in it is 3 feet deep. What is the area of the flowing water, in square feet?
  3. (2 points) Engineers find flow with the expression Q equals A times V. The area A is 24 square feet and the water speed V is 10 feet per second. What is Q, in cubic feet per second?
  4. (1 point) The design flood for Hearnside Dam is 240 cubic feet per second, and the proposed channel carries 240 cubic feet per second. Does the proposed channel pass the flood rule? Answer yes or no.
  5. (2 points) The wall of the proposed channel is 4 feet tall and the water in it is 3 feet deep. The gap between the water surface and the top of the wall is called freeboard. How many feet of freeboard does the proposed channel have?
  6. (2 points) The freeboard rule asks for at least 1.5 feet. The proposed channel has 1 foot. How many more feet of wall height would the plan need to meet the rule?
  7. (3 points) A second plan widens the channel to 12 feet and keeps the water speed at 10 feet per second. The channel must still carry 240 cubic feet per second. Using Q equals A times V, what water depth, in feet, would the wider channel need?
  8. (2 points) In the wider plan the water is 2 feet deep and the wall is still 4 feet tall. How many feet of freeboard does the wider channel have?
  9. (2 points) The 8-foot plan carries the flood but has 1 foot of freeboard. The 12-foot plan carries the flood and has 2 feet of freeboard. The rules are a flood capacity of 240 cubic feet per second and a freeboard of at least 1.5 feet. Which plan meets both rules?
    A. the 8-foot channel
    B. the 12-foot channel
    C. both plans
    D. neither plan
  10. (2 points) The 12-foot channel needs more concrete than the 8-foot channel. Give one reason the review panel might still approve the wider plan, and write one question the panel should ask before it votes.

From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.

Answer Key
  1. Answer: B.
    A spillway carries flood water past the dam so the lake does not rise over the dam itself. Choice A names a reservoir, choice C names a powerhouse, and choice D names a sediment forebay.
  2. Answer: 24 square feet.
    8 feet wide times 3 feet deep gives 24 square feet.
  3. Answer: 240 cubic feet per second.
    24 square feet times 10 feet per second gives 240 cubic feet per second.
  4. Answer: Yes.
    The channel carries exactly the 240 cubic feet per second the design flood delivers, so it passes the flood rule with nothing to spare.
  5. Answer: 1 foot.
    4 feet of wall minus 3 feet of water leaves 1 foot of freeboard.
  6. Answer: 0.5 foot.
    The rule asks for 1.5 feet and the plan has 1 foot, so the wall needs 0.5 foot more height.
  7. Answer: 2 feet.
    Rearranging Q equals A times V gives A equals Q divided by V, so A is 240 divided by 10, which is 24 square feet. Dividing 24 square feet by the 12-foot width gives a depth of 2 feet.
  8. Answer: 2 feet.
    4 feet of wall minus 2 feet of water leaves 2 feet of freeboard.
  9. Answer: B.
    The 8-foot channel passes the flood rule but its 1 foot of freeboard is under the 1.5-foot rule. The 12-foot channel passes both, with 2 feet of freeboard.
  10. Answer: The wider channel keeps freeboard in reserve.
    Accept any reason tied to a rule or a risk, such as the extra freeboard leaving room if the flood runs larger than predicted, or the shallower water being less likely to splash over the wall at a bend. Accept any question that would change the decision, such as how much more the wider channel costs, whether the wall could simply be raised on the 8-foot plan, or how the 240 cubic feet per second design flood was chosen.

Differentiation

Support

Provide a labeled cross-section drawing of the channel with the width, the water depth, the wall height, and the freeboard gap marked, and allow students to write on it. Supply the expression Q equals A times V at the top of the page with each letter named. Allow calculators.

Extension

Ask students to find the wall height that would give the 8-foot channel exactly 2 feet of freeboard, then write a short paragraph comparing that fix with widening the channel, naming one advantage of each.

ELL supports

Pre-teach "spillway," "freeboard," "design flood," and "channel" with the cross-section drawing and a photograph of a dam with water spilling over a chute. Allow item 10 to be answered in two short sentences, and provide the frame "The panel might approve it because ____. The panel should ask ____."