Flood Risk Assessment using Grass GIS - Revision history

Collin Godsell: /* Starting a GRASS session */

2023-09-29T21:46:11Z

Starting a GRASS session

Collin Godsell: /* Importing Vector Data into GRASS */

2023-09-29T21:07:17Z

Importing Vector Data into GRASS

Collin Godsell: /* The Data Panel */

2023-09-29T21:06:40Z

The Data Panel

Collin Godsell: /* Software and Data */

2023-09-29T21:06:11Z

Software and Data

Collin Godsell: /* Conclusion */

2023-09-29T21:05:09Z

Conclusion

Collin Godsell: /* Results */

2023-09-29T21:03:56Z

Results

Collin Godsell: /* Creating Flooding Scenarios */

2023-09-29T20:57:29Z

Creating Flooding Scenarios

Collin Godsell: /* Creating Flooding Scenarios */

2023-09-29T20:51:01Z

Creating Flooding Scenarios

Collin Godsell: /* Creating Flooding Scenarios */

2023-09-29T20:50:27Z

Creating Flooding Scenarios

Collin Godsell: /* Creating Flooding Scenarios */

2023-09-29T20:36:50Z

Creating Flooding Scenarios

@@ Line 40: / Line 40: @@
 : '''Let us being by creating a GRASS session:'''
 :First, open Grass GIS by clicking on the desktop icon; if your installer did not create a desktop shortcut manually search for the GRASS GIS app in your operating system's search bar
-:Next, you will see (any returning users will be shocked) that the GRASS GUI loads an automatic "demolocation"
+:Next, you will see (any returning users will be shocked) that the GRASS GUI loads an automatic "demolocation")
 [[File:StartupGRASS.png|frame|center]]
 :'''Notice:'''

@@ Line 144: / Line 144: @@
 ===Importing Vector Data into GRASS===
 The GRASS session is now setup, and we can start importing the data we collected from earlier, starting with the ''local area boundary'' file
-: 1. Either under the File tab or the Data panel, select the "Import Vector Data" tool [v.import]
+: '''1.''' Either under the File tab or the Data panel, select the "Import Vector Data" tool [v.import]
-: 2. '''Browse''' to the location you selected to extract our data and select the "local-area-boundary" Shapefile
+: '''2.''' '''Browse''' to the location you selected to extract our data and select the "local-area-boundary" Shapefile
-: 3. Ensure the '''Override Projection Check''' is selected allowing whatever projection our data is currently projected in (if projected at all) to be projected in the same format as the location we created
+: '''3.''' Ensure the '''Override Projection Check''' is selected allowing whatever projection our data is currently projected in (if projected at all) to be projected in the same format as the location we created
 [[File:LoadingBoundary.png|frame|left|Importing Vector Data into GRASS]]

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-: 1. The GRASS Database: This allows the user to add new/existing databases and remove them as well
+: '''1.''' The GRASS Database: This allows the user to add new/existing databases and remove them as well
-: 2. The project's location: This feature allows the user to specify a location which is essentially a sub-directory in the database
+: '''2.''' The project's location: This feature allows the user to specify a location which is essentially a sub-directory in the database
-: 3. Creating a Mapset: This allows the user to create a new map workspace much like the already created "PERMANENT" mapset
+: '''3.''' Creating a Mapset: This allows the user to create a new map workspace much like the already created "PERMANENT" mapset

@@ Line 9: / Line 9: @@
 The data used for this lesson are derived from two main sources, the US Geological Survey Earth Explorer tool ([https://earthexplorer.usgs.gov/]) and the City of Vancouver Open Data website ([https://opendata.vancouver.ca/pages/home/]); both are open data sources, although the USGS requires you to create an account to access their data.
+==Vancouver Open Data==
 First, let's begin by collecting the data needed from the City of Vancouver Open Data Website:
 : 1. Open the link provided above
@@ Line 19: / Line 20: @@
 : 8. Store the data in a folder you'll keep tabs on (we will export it to the GRASS database later)
+==USGS Earth Explorer==
 Next, we will collect the data from the Earth Explorer website:
 : 1. Open the link provided from above

@@ Line 235: / Line 235: @@
 : - The results clearly display the more ravaging effects on infrastructure and subsequently people with the simulated severe case of flooding.
-==Results==
+==Conclusion==
 : -  After having created 3 separate raster layers, representing (although crudely) 6 meter flooding, 9 meter flooding and 20 meter flooding respectively, we can complete our assessment by toggling the layers on and off in the panel to contrast the differences in impact of each flood level.
 : - Although this was just a basic assessment of flood levels conducted on GRASS GIS, the fundamentals of this tutorial are re-applicable to much more in depth analysis and have effectively equipped you with the knowledge and resources to expand to much higher level results.

@@ Line 203: / Line 203: @@
 ===Creating Flooding Scenarios===
-: 1. Under the '''Raster''' tab, navigate to the "Raster map calculator" drop-down and select "Raster map calculator" [r.mapcalc], not to be confused with the simple raster calculator
+: '''1.''' Under the '''Raster''' tab, navigate to the "Raster map calculator" drop-down and select "Raster map calculator" [r.mapcalc], not to be confused with the simple raster calculator
-: 2. Input this expression to simulate water levels of 6m: VancouverFlood6m = '''( (  VancouverDEM@VancouverFLoods  <= 6 ) ==  1 ) & ( ( VancouverDEM@VancouverFLoods   >= 6 ) ==  0 ) *supplement VancouverDEM with whatever you named the ''SRTM DEM'' file*
+: '''2.''' Input this expression to simulate water levels of 6m: VancouverFlood6m = '''( (  VancouverDEM@VancouverFLoods  <= 6 ) ==  1 ) & ( ( VancouverDEM@VancouverFLoods   >= 6 ) ==  0 ) *supplement VancouverDEM with whatever you named the ''SRTM DEM'' file*
 : '''Note''' @VancouverFLoods is the name of the current mapset
-: 3. Click on '''Run'''
+: '''3.''' Click on '''Run'''
 : '''Before Simulated Flooding '''
@@ Line 221: / Line 221: @@
 : - Next let's simulate the effects of 9 meters of flood water to see if there is any significant difference in impact.
-: 1. Under the '''Raster''' tab, select '''Raster map calculator''' [r.mapcalc]
+: '''1.''' Under the '''Raster''' tab, select '''Raster map calculator''' [r.mapcalc]
-: 2. Input this expression to simulate water levels of 9m: VancouverFlood9m = '''( (  VancouverDEM@VancouverFLoods  <= 9 ) ==  1 ) & ( ( VancouverDEM@VancouverFLoods   >= 9 ) ==  0 )''' *supplement VancouverDEM with whatever you named the ''SRTM DEM'' file*
+: '''2.''' Input this expression to simulate water levels of 9m: VancouverFlood9m = '''( (  VancouverDEM@VancouverFLoods  <= 9 ) ==  1 ) & ( ( VancouverDEM@VancouverFLoods   >= 9 ) ==  0 )''' *supplement VancouverDEM with whatever you named the ''SRTM DEM'' file*
-: 3. Click on '''Run'''
+: '''3.''' Click on '''Run'''
 :'''Simulated Flooding of 9 Meters'''
 [[File:9mFLood.png|frame|center|The simulated result of 9 meter flood waters in Vancouver BC]]
+: - It is clear the resulting Raster is representing a similar relationship to the last, but now symbolizing 9 meters rather than 6 meters. Finally, we will demonstrate a severe case of flooding at 20 meter flood waters.
+: - Modify the existing equation to simulate 20 meter flood waters: VancouverFlood20m = '''( (  VancouverDEM@VancouverFLoods  <= 20 ) ==  1 ) & ( ( VancouverDEM@VancouverFLoods   >= 20 ) ==  0 )'''
+[[File:Severeflooding.png|frame|center|The simulated result of 20 meter flood waters in Vancouver BC]]
+: - The results clearly display the more ravaging effects on infrastructure and subsequently people with the simulated severe case of flooding.
 ==Results==

@@ Line 203: / Line 203: @@
 ===Creating Flooding Scenarios===
-: 1. Under the '''Raster''' tab, select '''Raster map calculator''' [r.mapcalc]
+: 1. Under the '''Raster''' tab, navigate to the "Raster map calculator" drop-down and select "Raster map calculator" [r.mapcalc], not to be confused with the simple raster calculator
-: 2. Input this expression to simulate water levels of 6m: DaytonaFLOOD2m = '''( (  DaytonaSRTM@PERMANENT  <= 6 ) ==  1 ) & ( ( DaytonaSRTM@PERMANENT   >= 6 ) ==  0 ) *supplement DaytonaSRTM with whatever you named the ''SRTM DEM'' file*
+: 2. Input this expression to simulate water levels of 6m: VancouverFlood = '''( (  VancouverDEM@VancouverFLoods  <= 6 ) ==  1 ) & ( ( VancouverDEM@VancouverFLoods   >= 6 ) ==  0 ) *supplement VancouverDEM with whatever you named the ''SRTM DEM'' file*
+: '''Note''' @VancouverFLoods is the name of the current mapset
 : 3. Click on '''Run''', make sure the ''Add created raster map into layer tree'' option is selected before doing so
+: '''Before Simulated Flooding '''
+[[File:BeforeFloods.png|frame|center|Vancouver BC before simulated flooding]]
+:'''After Simulated Flooding'''
+[[File:AfterFloods.png|frame|center|The simulated result of 6 meter flood waters in Vancouver BC]]
 The resultant raster map shows which areas are inundated (yellow) and the non-inundated areas (purple) at 2m sea level rise. Next we will create another raster map showing an example of 5m of rising sea level.
 : 1. Under the '''Raster''' tab, select '''Raster map calculator''' [r.mapcalc]
-: 2. Input this expression to simulate water levels of 6m: DaytonaFLOOD2m = '''( (  DaytonaSRTM@PERMANENT  <= 9 ) ==  1 ) & ( ( DaytonaSRTM@PERMANENT   >= 9 ) ==  0 ) *supplement DaytonaSRTM with whatever you named the ''SRTM DEM'' file*
+: 2. Input this expression to simulate water levels of 9m: DaytonaFLOOD2m = '''( (  DaytonaSRTM@PERMANENT  <= 9 ) ==  1 ) & ( ( DaytonaSRTM@PERMANENT   >= 9 ) ==  0 ) *supplement DaytonaSRTM with whatever you named the ''SRTM DEM'' file*
 : 3. Click on '''Run''', make sure the ''Add created raster map into layer tree'' option is selected before doing so