Read layered maps the way GIS does: overlay and find the pattern

Grade 9 Social Studies Worksheet - Challenge Me

Circle the best answer.

1. Read this first

   Use this

   Card F (made up for practice). Marlow's flood map in 2010 and in 2020. 2010: 40 homes; the flood zone is a strip along Mill Creek, and 6 homes lie inside it. 2020: 52 homes; the zone was redrawn wider after new measurements, and 11 homes lie inside the 2020 zone; 8 of the 52 homes lie inside the old 2010 strip. The 2020 zone includes the old 2010 strip. Key: shading = flood zone; small square = home. Note: a GIS overlay counts the homes where the layers overlap.

2. 1.

   Ari asks how much of the rise in the share came from new homes alone. Using the old 2010 strip on the 2020 homes, what is the share?

   • About 15.4% (8 of 52), barely above 15.0%, so new building alone moved the share very little
   • About 31% (8 + 8 of 52), because the old-strip homes count once for 2010 and again for 2020
   • About 21% (11 of 52), because the new homes are the reason the 2020 share is up
   • About 20% (8 of 40), because 8 is the number of homes in the old strip and 40 is the 2010 base

3. Use this

   Card F (made up for practice). Marlow's flood map in 2010 and in 2020. 2010: 40 homes; the flood zone is a strip along Mill Creek, and 6 homes lie inside it. 2020: 52 homes; the zone was redrawn wider after new measurements, and 11 homes lie inside the 2020 zone; 8 of the 52 homes lie inside the old 2010 strip. The 2020 zone includes the old 2010 strip. Key: shading = flood zone; small square = home. Note: a GIS overlay counts the homes where the layers overlap. Card H (made up for practice). Two readings of Card F. Reading X: "The share of homes in the flood zone rose because people kept building in risky places." Reading Y: "The share rose because the zone was redrawn wider."

4. 2.

   Luz checks Reading X (building in risky places) and Reading Y (zone redrawn) against Card F. Which statement holds?

   • Neither can be tested with Card F, because it gives counts of homes and not the reasons people built where they did
   • Both contribute, but Y more: new homes lifted the share by about 0.4 points and the redrawn zone by about 5.8
   • X explains it, since 11 homes now lie in the zone against 6 before and the new homes were built in the zone
   • Y alone explains it, because the old-strip share did not change and so building played no part

5. Use this

   Card F (made up for practice). Marlow's flood map in 2010 and in 2020. 2010: 40 homes; the flood zone is a strip along Mill Creek, and 6 homes lie inside it. 2020: 52 homes; the zone was redrawn wider after new measurements, and 11 homes lie inside the 2020 zone; 8 of the 52 homes lie inside the old 2010 strip. The 2020 zone includes the old 2010 strip. Key: shading = flood zone; small square = home. Note: a GIS overlay counts the homes where the layers overlap.

6. 3.

   Tala counts what the redrawn zone added in 2020. How many homes are inside the 2020 zone but outside the old 2010 strip?

   • Nineteen homes, the 11 in the 2020 zone plus the 8 in the old strip, because OR adds the two layers
   • Five homes, the 11 in the 2020 zone minus the 6 that were in the zone in 2010
   • Twelve homes, the 52 homes in 2020 minus the 40 homes counted in 2010
   • Three homes, the 11 inside the 2020 zone minus the 8 that were already inside the old strip

7. Use this

   Card G (made up for practice). Marlow's roads and services in 2020. Three roads: Mill Road, Oak Road and Ridge Road. Mill Road and Oak Road cross the 2020 flood zone at bridges; Ridge Road does not. The clinic stands on Ridge Road. Of the 11 homes inside the zone, 7 stand on Mill Road or Oak Road and 4 stand on a side street that joins Oak Road inside the zone. Key: shading = flood zone; line = road; cross = clinic.

8. 4.

   Jun asks how many of the 11 zone homes are on a road that does NOT cross the zone at a bridge. Using Card G, what is the count?

   • Eleven, since the flood layer shades the zone homes, and no zone home is on a road that avoids the zone
   • None: all 11 are on Mill Road, Oak Road or a side street joining Oak Road, and Ridge Road holds none
   • Seven, the homes on Mill Road or Oak Road, since those roads cross the zone at bridges
   • Four, the homes on the side street, which is not itself one of the three named roads

9. Use this

   Card F (made up for practice). Marlow's flood map in 2010 and in 2020. 2010: 40 homes; the flood zone is a strip along Mill Creek, and 6 homes lie inside it. 2020: 52 homes; the zone was redrawn wider after new measurements, and 11 homes lie inside the 2020 zone; 8 of the 52 homes lie inside the old 2010 strip. The 2020 zone includes the old 2010 strip. Key: shading = flood zone; small square = home. Note: a GIS overlay counts the homes where the layers overlap. Card G (made up for practice). Marlow's roads and services in 2020. Three roads: Mill Road, Oak Road and Ridge Road. Mill Road and Oak Road cross the 2020 flood zone at bridges; Ridge Road does not. The clinic stands on Ridge Road. Of the 11 homes inside the zone, 7 stand on Mill Road or Oak Road and 4 stand on a side street that joins Oak Road inside the zone. Key: shading = flood zone; line = road; cross = clinic.

10. 5.

    Pia runs: inside the 2020 flood zone AND on Mill Road or Oak Road. What share of the 52 homes does it keep?

    • About 35% (18 of 52), because OR adds the 11 zone homes and the 7 on those roads
    • About 64% (7 of 11), since the query keeps homes in the zone
    • About 21% (11 of 52), since the 11 zone homes are on a road that crosses the zone
    • About 13.5% (7 of 52), the zone homes that stand on Mill Road or Oak Road

11. Use this

    Card G (made up for practice). Marlow's roads and services in 2020. Three roads: Mill Road, Oak Road and Ridge Road. Mill Road and Oak Road cross the 2020 flood zone at bridges; Ridge Road does not. The clinic stands on Ridge Road. Of the 11 homes inside the zone, 7 stand on Mill Road or Oak Road and 4 stand on a side street that joins Oak Road inside the zone. Key: shading = flood zone; line = road; cross = clinic.

12. 6.

    Bo reads Card G: the clinic is on Ridge Road, which does not cross the zone. What follows for the 11 zone homes?

    • The clinic is in the zone, since the flood layer covers the road layer on the map
    • Ridge Road avoids the zone, but the card gives no route from each home to it, so access is not shown
    • Nothing about the clinic can be said, because the layers show roads and not buildings
    • The 11 homes can reach the clinic without crossing the zone, since the clinic is on a road that avoids it
13. 7.

    Milo runs: inside the 2020 flood zone AND NOT on Mill Road or Oak Road. Which homes does Card G leave?

    • The 7 homes on Mill Road or Oak Road, because the NOT part keeps those roads and removes the others
    • The 11 homes in the zone, since the query removes roads from the map and not homes from the zone
    • No homes, because the homes in the zone stand on a road that crosses the zone at a bridge
    • The 4 homes on the side street that joins Oak Road inside the zone

14. Use this

    Card F (made up for practice). Marlow's flood map in 2010 and in 2020. 2010: 40 homes; the flood zone is a strip along Mill Creek, and 6 homes lie inside it. 2020: 52 homes; the zone was redrawn wider after new measurements, and 11 homes lie inside the 2020 zone; 8 of the 52 homes lie inside the old 2010 strip. The 2020 zone includes the old 2010 strip. Key: shading = flood zone; small square = home. Note: a GIS overlay counts the homes where the layers overlap. Card H (made up for practice). Two readings of Card F. Reading X: "The share of homes in the flood zone rose because people kept building in risky places." Reading Y: "The share rose because the zone was redrawn wider."

15. 8.

    Zee writes: "The share rose from 15% to 21%, so the flood risk per home rose by 6%." What is the best correction using Card F?

    • The share is the same in both years if the 2010 strip is used, so there is no rise to correct
    • The rise is 6 percent, as written, because 21 minus 15 is 6 and percent is the unit of a share
    • The share rose about 6 points, a 41% rise, and a zone's share is not the risk to a home
    • The note is right about the share and risk, because a home inside the zone is flooded in each storm

16. Use this

    Card F (made up for practice). Marlow's flood map in 2010 and in 2020. 2010: 40 homes; the flood zone is a strip along Mill Creek, and 6 homes lie inside it. 2020: 52 homes; the zone was redrawn wider after new measurements, and 11 homes lie inside the 2020 zone; 8 of the 52 homes lie inside the old 2010 strip. The 2020 zone includes the old 2010 strip. Key: shading = flood zone; small square = home. Note: a GIS overlay counts the homes where the layers overlap. Card G (made up for practice). Marlow's roads and services in 2020. Three roads: Mill Road, Oak Road and Ridge Road. Mill Road and Oak Road cross the 2020 flood zone at bridges; Ridge Road does not. The clinic stands on Ridge Road. Of the 11 homes inside the zone, 7 stand on Mill Road or Oak Road and 4 stand on a side street that joins Oak Road inside the zone. Key: shading = flood zone; line = road; cross = clinic.

17. 9.

    Ren writes: "Only 11 of 52 homes are at risk, so the clinic and roads are safe." What is the best correction using Cards F and G?

    • The note is wrong because 11 of 52 is more than a fifth, which is too many for the roads to be safe
    • Homes outside the zone can still lose road access, because Mill Road and Oak Road cross the zone at bridges
    • The note is right for the clinic, since it is on Ridge Road, and wrong for the three roads
    • The note is right, since homes outside the zone are not shaded and so cannot be affected by a flood

18. Use this

    Card F (made up for practice). Marlow's flood map in 2010 and in 2020. 2010: 40 homes; the flood zone is a strip along Mill Creek, and 6 homes lie inside it. 2020: 52 homes; the zone was redrawn wider after new measurements, and 11 homes lie inside the 2020 zone; 8 of the 52 homes lie inside the old 2010 strip. The 2020 zone includes the old 2010 strip. Key: shading = flood zone; small square = home. Note: a GIS overlay counts the homes where the layers overlap. Card H (made up for practice). Two readings of Card F. Reading X: "The share of homes in the flood zone rose because people kept building in risky places." Reading Y: "The share rose because the zone was redrawn wider."

19. 10.

    Esme writes: "Reading X is false, because the old-strip share barely moved." What is the best correction using Cards F and H?

    • Reading X is weak, not false: new building raised the old-strip share from 15.0% to 15.4%, a small effect
    • Reading X is the main cause, because the old-strip share rose and the new homes were built in the zone
    • The note is right, since a rise of 0.4 points is within rounding and so no effect
    • Reading X cannot be tested, because the card does not give the builders' reasons