{"id":335712,"date":"2018-10-16T10:30:02","date_gmt":"2018-10-16T17:30:02","guid":{"rendered":"http:\/\/www.esri.com\/arcgis-blog\/?post_type=blog&p=335712"},"modified":"2021-01-26T08:53:42","modified_gmt":"2021-01-26T16:53:42","slug":"determine-flood-risk","status":"publish","type":"blog","link":"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-online\/analytics\/determine-flood-risk","title":{"rendered":"Determine flood risk for disaster response"},"author":6771,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"open","ping_status":"closed","template":"","format":"standard","meta":{"_acf_changed":false,"_searchwp_excluded":""},"categories":[23341],"tags":[26121,25501,35021,25071,100192],"industry":[],"product":[36551],"class_list":["post-335712","blog","type-blog","status-publish","format-standard","hentry","category-analytics","tag-disaster-response","tag-flood","tag-houston","tag-learn-arcgis","tag-learn-by-doing","product-arcgis-online"],"acf":{"short_description":"Use spatial analysis in ArcGIS Online to find areas that need evacuation assistance after a flood.","flexible_content":[{"acf_fc_layout":"content","content":"

Natural disasters, such as hurricanes and flooding, often require evacuations for safety reasons.\u00a0 However, there is often a large portion of the population that ends up staying behind through the storm.\u00a0 Sometimes people choose to stay behind despite an evacuation order; other people are unable to evacuate due to many factors, such as age, disabilities, and illness; and sometimes officials do not issue an evacuation order at all.<\/p>\n

In this lesson you’ll perform suitability analysis<\/a> to create a web map of flood risk\u00a0in Houston, Texas that can help emergency response workers respond to the areas with the highest potential need for evacuation when a flood occurs.<\/p>\n"},{"acf_fc_layout":"storymap","title":"","description":"","static":false,"storymap_url":"https:\/\/arcgis.com\/apps\/Embed\/index.html?webmap=d38062f2611d49d8b2a718d10e03b722<\/a>"},{"acf_fc_layout":"content","content":"

Step 1: Determine the suitability criteria and collect your data<\/h2>\n

First you\u2019ll determine the suitability criteria for Houston, Texas and collect the appropriate data.<\/p>\n

1. Sign in to an ArcGIS account and click Map<\/strong>.<\/p>\n"},{"acf_fc_layout":"sidebar","content":"

This lesson requires an ArcGIS account, privileges to perform spatial analysis, and access to subscriber content. If you don’t have these privileges, contact your administrator or join the Learn ArcGIS<\/a> organization for a free 60-day membership.<\/p>\n","image_reference":false,"layout":"standard","image_reference_figure":"","snippet":"","spotlight_name":"","section_title":"","position":"Center","spotlight_image":false},{"acf_fc_layout":"content","content":"

2. In the Find address or place<\/strong> text box, search for Houston, TX, USA<\/strong>. The map zooms to Houston.<\/p>\n

To make sure your analysis is contained within Houston, you\u2019ll add a city boundary.<\/p>\n

3. On the ribbon, click Add<\/strong> and choose Search for Layers<\/strong>.<\/p>\n

4. Click the arrow next to My Content<\/strong> and choose ArcGIS Online<\/strong>.<\/p>\n

5. Search for World Urban Areas<\/strong>.<\/p>\n

The top result is a layer published by Esri.\u00a0 It looks like a trusted source.<\/p>\n

6. Click the Add<\/strong> button to add the layer to your map.<\/p>\n"},{"acf_fc_layout":"image","image":{"ID":1056641,"id":1056641,"title":"Add-layer","filename":"Add-layer.png","filesize":10434,"url":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/Add-layer.png","link":"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-online\/analytics\/determine-flood-risk\/add-layer-2","alt":"Search for and add World Urban Areas to your map","author":"6771","description":"","caption":"","name":"add-layer-2","status":"inherit","uploaded_to":335712,"date":"2020-11-05 15:22:59","modified":"2020-11-05 15:23:38","menu_order":0,"mime_type":"image\/png","type":"image","subtype":"png","icon":"https:\/\/www.esri.com\/arcgis-blog\/wp-includes\/images\/media\/default.png","width":575,"height":311,"sizes":{"thumbnail":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/Add-layer-213x200.png","thumbnail-width":213,"thumbnail-height":200,"medium":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/Add-layer.png","medium-width":464,"medium-height":251,"medium_large":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/Add-layer.png","medium_large-width":575,"medium_large-height":311,"large":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/Add-layer.png","large-width":575,"large-height":311,"1536x1536":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/Add-layer.png","1536x1536-width":575,"1536x1536-height":311,"2048x2048":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/Add-layer.png","2048x2048-width":575,"2048x2048-height":311,"card_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/Add-layer.png","card_image-width":575,"card_image-height":311,"wide_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/Add-layer.png","wide_image-width":575,"wide_image-height":311}},"image_position":"center","orientation":"horizontal","hyperlink":""},{"acf_fc_layout":"content","content":"

Your analysis is based around responding to flooding events, so you want to incorporate flood zones as one of your criteria.<\/p>\n

7. In the search bar, do a new search for HarrisCountyFloodZones owner:Learn_ArcGIS<\/strong>.<\/p>\n

8. Add the returned layer to the map.<\/p>\n

One of the major factors in evacuations for Houston is the proximity to an evacuation route.<\/p>\n

9. In the search bar, search for hurricane evacuation routes<\/strong>.<\/p>\n

10. Click the Add<\/strong> button to add the Hurricane Evacuation Routes<\/strong> layer from the Federal User Community to your map.<\/p>\n

Vehicle ownership can affect people\u2019s ability to evacuate. You\u2019ll use this demographic data in your analysis.<\/p>\n

11. In the search bar, search Houston demographics owner:Learn_ArcGIS<\/strong>.<\/p>\n

12. Click the Add<\/strong> button to add the Houston Census Tract Demographics<\/strong>\u00a0layer to your map.<\/p>\n

Your map should now have four data layers: Houston Census Tract Demographics<\/strong>, Hurricane Evacuation Routes<\/strong>, World Urban Areas<\/strong>, and HarrisCountyFloodZones<\/strong>.<\/p>\n

13. Click the arrow to return to the Contents<\/strong> pane view.<\/p>\n

14. Uncheck the Houston Census Tract Demographics<\/strong>\u00a0to turn off the layer and make it easier to see the rest of the data.<\/p>\n"},{"acf_fc_layout":"image","image":{"ID":1056651,"id":1056651,"title":"All-layers","filename":"All-layers.png","filesize":52200,"url":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/All-layers.png","link":"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-online\/analytics\/determine-flood-risk\/all-layers","alt":"Houston boundary, evacuation routes, and flood risk area layers","author":"6771","description":"","caption":"","name":"all-layers","status":"inherit","uploaded_to":335712,"date":"2020-11-05 15:30:01","modified":"2020-11-05 15:30:31","menu_order":0,"mime_type":"image\/png","type":"image","subtype":"png","icon":"https:\/\/www.esri.com\/arcgis-blog\/wp-includes\/images\/media\/default.png","width":601,"height":360,"sizes":{"thumbnail":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/All-layers-213x200.png","thumbnail-width":213,"thumbnail-height":200,"medium":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/All-layers.png","medium-width":436,"medium-height":261,"medium_large":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/All-layers.png","medium_large-width":601,"medium_large-height":360,"large":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/All-layers.png","large-width":601,"large-height":360,"1536x1536":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/All-layers.png","1536x1536-width":601,"1536x1536-height":360,"2048x2048":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/All-layers.png","2048x2048-width":601,"2048x2048-height":360,"card_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/All-layers.png","card_image-width":601,"card_image-height":360,"wide_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/All-layers.png","wide_image-width":601,"wide_image-height":360}},"image_position":"center","orientation":"horizontal","hyperlink":""},{"acf_fc_layout":"content","content":"

Step 2: Prepare the data for analysis<\/h2>\n

Now that you\u2019ve collected your data, you need to prepare it to find risk areas. In this case you will use proximity to evacuation routes, proximity to flood zones, and vehicle ownership to determine risk. All of the risk zones will be within the Houston city limit.<\/p>\n

The World Urban Areas<\/strong> layer includes boundaries of cities all around the world.\u00a0 You only need the Houston boundary so you\u2019ll filter out the rest.<\/p>\n

1. Click the Filter<\/strong> button below World Urban Areas<\/strong>. The Filter<\/strong> window opens.<\/p>\n"},{"acf_fc_layout":"image","image":{"ID":336512,"id":336512,"title":"filter-icon-world-urban-areas","filename":"filter-icon-world-urban-areas.png","filesize":2069,"url":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/filter-icon-world-urban-areas.png","link":"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-online\/analytics\/determine-flood-risk\/filter-icon-world-urban-areas","alt":"","author":"6771","description":"","caption":"","name":"filter-icon-world-urban-areas","status":"inherit","uploaded_to":335712,"date":"2018-10-03 18:02:03","modified":"2018-10-03 18:04:39","menu_order":0,"mime_type":"image\/png","type":"image","subtype":"png","icon":"https:\/\/www.esri.com\/arcgis-blog\/wp-includes\/images\/media\/default.png","width":411,"height":43,"sizes":{"thumbnail":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/filter-icon-world-urban-areas.png","thumbnail-width":213,"thumbnail-height":22,"medium":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/filter-icon-world-urban-areas.png","medium-width":411,"medium-height":43,"medium_large":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/filter-icon-world-urban-areas.png","medium_large-width":411,"medium_large-height":43,"large":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/filter-icon-world-urban-areas.png","large-width":411,"large-height":43,"1536x1536":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/filter-icon-world-urban-areas.png","1536x1536-width":411,"1536x1536-height":43,"2048x2048":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/filter-icon-world-urban-areas.png","2048x2048-width":411,"2048x2048-height":43,"card_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/filter-icon-world-urban-areas.png","card_image-width":411,"card_image-height":43,"wide_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/filter-icon-world-urban-areas.png","wide_image-width":411,"wide_image-height":43}},"image_position":"center","orientation":"horizontal","hyperlink":""},{"acf_fc_layout":"content","content":"

2. Create the expression Name is Houston<\/span>.<\/p>\n"},{"acf_fc_layout":"image","image":{"ID":338062,"id":338062,"title":"filter_name_is_houston","filename":"filter_name_is_houston2.png","filesize":11919,"url":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/filter_name_is_houston2.png","link":"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-online\/analytics\/determine-flood-risk\/filter_name_is_houston2","alt":"","author":"6771","description":"","caption":"","name":"filter_name_is_houston2","status":"inherit","uploaded_to":335712,"date":"2018-10-04 13:58:08","modified":"2018-10-04 13:58:52","menu_order":0,"mime_type":"image\/png","type":"image","subtype":"png","icon":"https:\/\/www.esri.com\/arcgis-blog\/wp-includes\/images\/media\/default.png","width":600,"height":193,"sizes":{"thumbnail":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/filter_name_is_houston2.png","thumbnail-width":213,"thumbnail-height":69,"medium":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/filter_name_is_houston2.png","medium-width":464,"medium-height":149,"medium_large":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/filter_name_is_houston2.png","medium_large-width":600,"medium_large-height":193,"large":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/filter_name_is_houston2.png","large-width":600,"large-height":193,"1536x1536":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/filter_name_is_houston2.png","1536x1536-width":600,"1536x1536-height":193,"2048x2048":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/filter_name_is_houston2.png","2048x2048-width":600,"2048x2048-height":193,"card_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/filter_name_is_houston2.png","card_image-width":600,"card_image-height":193,"wide_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/filter_name_is_houston2.png","wide_image-width":600,"wide_image-height":193}},"image_position":"center","orientation":"horizontal","hyperlink":""},{"acf_fc_layout":"sidebar","content":"

Proximity to flood zones represents risk of not evacuating, while proximity to roads represents ability to evacuate. One way to incorporate these proximities would be to run the Create Buffers tool.\u00a0 However, there are several tools in ArcGIS Online that allow you to incorporate proximity without creating a buffer first.<\/p>\n","image_reference":false,"layout":"standard","image_reference_figure":"","snippet":"","spotlight_name":"","section_title":"","position":"Right","spotlight_image":false},{"acf_fc_layout":"content","content":"

3. Click Apply filter<\/strong>. The layer now only has one feature: the Houston city boundary.<\/p>\n

To set an accurate threshold of low vehicle ownership, you need to take a look at some related statistics.<\/p>\n

4. Click Show Table<\/strong> for the Houston Census Tract Demographics<\/strong>\u00a0layer. The attribute table opens.<\/p>\n

5. Find the field Owner\/Renter Households without a Vehicle (ACS 2013-2017)<\/strong>.<\/p>\n

6. Click the field and choose Statistics<\/strong> from the menu. Note the Average<\/strong> value is 107.01 and the Standard Deviation<\/strong> is 105.74. You will use those values for setting your thresholds.<\/p>\n"},{"acf_fc_layout":"image","image":{"ID":1056661,"id":1056661,"title":"statistics","filename":"statistics.png","filesize":8140,"url":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/statistics.png","link":"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-online\/analytics\/determine-flood-risk\/statistics","alt":"Calculate the statistics for Houston Census Tract Demographics","author":"6771","description":"","caption":"","name":"statistics","status":"inherit","uploaded_to":335712,"date":"2020-11-05 15:38:07","modified":"2020-11-05 15:38:40","menu_order":0,"mime_type":"image\/png","type":"image","subtype":"png","icon":"https:\/\/www.esri.com\/arcgis-blog\/wp-includes\/images\/media\/default.png","width":355,"height":393,"sizes":{"thumbnail":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/statistics-213x200.png","thumbnail-width":213,"thumbnail-height":200,"medium":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/statistics.png","medium-width":236,"medium-height":261,"medium_large":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/statistics.png","medium_large-width":355,"medium_large-height":393,"large":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/statistics.png","large-width":355,"large-height":393,"1536x1536":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/statistics.png","1536x1536-width":355,"1536x1536-height":393,"2048x2048":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/statistics.png","2048x2048-width":355,"2048x2048-height":393,"card_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/statistics.png","card_image-width":355,"card_image-height":393,"wide_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/statistics.png","wide_image-width":355,"wide_image-height":393}},"image_position":"left-center","orientation":"horizontal","hyperlink":""},{"acf_fc_layout":"content","content":"

Step 3: Query the data<\/h2>\n

You\u2019ll use Derive New Locations<\/a> for your suitability analysis. Using the tool, you\u2019ll weight demographic criteria like poverty and vehicle access with proximity to floodplains to identify at-risk areas in Houston.<\/p>\n

1. Click the Perform Analysis<\/strong> button under the Houston Census Tract Demographics<\/strong>\u00a0layer.<\/p>\n"},{"acf_fc_layout":"image","image":{"ID":1056671,"id":1056671,"title":"perform-analysis-button","filename":"perform-analysis-button.png","filesize":2141,"url":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/perform-analysis-button.png","link":"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-online\/analytics\/determine-flood-risk\/perform-analysis-button","alt":"The Perform Analysis button","author":"6771","description":"","caption":"","name":"perform-analysis-button","status":"inherit","uploaded_to":335712,"date":"2020-11-05 15:41:19","modified":"2020-11-05 15:41:44","menu_order":0,"mime_type":"image\/png","type":"image","subtype":"png","icon":"https:\/\/www.esri.com\/arcgis-blog\/wp-includes\/images\/media\/default.png","width":356,"height":44,"sizes":{"thumbnail":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/perform-analysis-button-213x44.png","thumbnail-width":213,"thumbnail-height":44,"medium":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/perform-analysis-button.png","medium-width":356,"medium-height":44,"medium_large":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/perform-analysis-button.png","medium_large-width":356,"medium_large-height":44,"large":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/perform-analysis-button.png","large-width":356,"large-height":44,"1536x1536":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/perform-analysis-button.png","1536x1536-width":356,"1536x1536-height":44,"2048x2048":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/perform-analysis-button.png","2048x2048-width":356,"2048x2048-height":44,"card_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/perform-analysis-button.png","card_image-width":356,"card_image-height":44,"wide_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/perform-analysis-button.png","wide_image-width":356,"wide_image-height":44}},"image_position":"left-center","orientation":"horizontal","hyperlink":""},{"acf_fc_layout":"sidebar","content":"

A suitability analysis requires an overlay of layers to find the areas where all your criteria are met.\u00a0 This is accomplished using Find Existing Locations<\/a> or Derive New Locations.\u00a0 The queries are built the same, but Find Existing Locations returns full features whereas Derive New Locations returns only the exact areas that fit the criteria.<\/p>\n","image_reference":false,"layout":"standard","image_reference_figure":"","snippet":"","spotlight_name":"","section_title":"","position":"Left","spotlight_image":false},{"acf_fc_layout":"content","content":"

2. Expand the Find Locations<\/strong> toolset. Choose the Derive New Locations<\/strong> tool.<\/p>\n

3. Click Add Expression<\/strong>.<\/p>\n

You\u2019ll start with the highest risk areas. The ability to evacuate is based partly on households without vehicles. You\u2019ll use the sum of the mean (107) and the standard deviation (106) to determine the threshold for Census tracts with a high number of households without vehicles. These are the values you got from looking at the table.<\/p>\n

4. Change the query to Houston Census Tract Demographics where (attribute query) Owner\/Renter Households without a Vehicle (ACS 2013-2017) is greater than 213<\/span>.<\/p>\n"},{"acf_fc_layout":"image","image":{"ID":1056681,"id":1056681,"title":"Add-expression","filename":"Add-expression.png","filesize":6598,"url":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/Add-expression.png","link":"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-online\/analytics\/determine-flood-risk\/add-expression-2","alt":"Add an attribute expression in the Derive New Locations tool","author":"6771","description":"","caption":"","name":"add-expression-2","status":"inherit","uploaded_to":335712,"date":"2020-11-05 15:45:08","modified":"2020-11-05 15:45:47","menu_order":0,"mime_type":"image\/png","type":"image","subtype":"png","icon":"https:\/\/www.esri.com\/arcgis-blog\/wp-includes\/images\/media\/default.png","width":753,"height":235,"sizes":{"thumbnail":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/Add-expression-213x200.png","thumbnail-width":213,"thumbnail-height":200,"medium":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/Add-expression.png","medium-width":464,"medium-height":145,"medium_large":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/Add-expression.png","medium_large-width":753,"medium_large-height":235,"large":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/Add-expression.png","large-width":753,"large-height":235,"1536x1536":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/Add-expression.png","1536x1536-width":753,"1536x1536-height":235,"2048x2048":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/Add-expression.png","2048x2048-width":753,"2048x2048-height":235,"card_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/Add-expression.png","card_image-width":753,"card_image-height":235,"wide_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/Add-expression.png","wide_image-width":753,"wide_image-height":235}},"image_position":"left-center","orientation":"horizontal","hyperlink":""},{"acf_fc_layout":"content","content":"

5. Click Add<\/strong> to add the query to the expression.<\/p>\n

Next you\u2019ll start making spatial queries. The first one is based on the Houston city boundary.<\/p>\n

6. Click Add Expression<\/strong>.<\/p>\n

7. Change the expression to Houston Census Tract Demographics intersects World Urban Areas<\/span>. This query means that all the areas returned will be within the Houston city boundary.<\/p>\n"},{"acf_fc_layout":"image","image":{"ID":1056691,"id":1056691,"title":"Add-spatial-expression","filename":"Add-spatial-expression.png","filesize":4730,"url":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/Add-spatial-expression.png","link":"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-online\/analytics\/determine-flood-risk\/add-spatial-expression","alt":"Add a spatial expression in the Derive New Locations tool","author":"6771","description":"","caption":"","name":"add-spatial-expression","status":"inherit","uploaded_to":335712,"date":"2020-11-05 15:47:52","modified":"2020-11-05 15:48:59","menu_order":0,"mime_type":"image\/png","type":"image","subtype":"png","icon":"https:\/\/www.esri.com\/arcgis-blog\/wp-includes\/images\/media\/default.png","width":510,"height":199,"sizes":{"thumbnail":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/Add-spatial-expression-213x199.png","thumbnail-width":213,"thumbnail-height":199,"medium":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/Add-spatial-expression.png","medium-width":464,"medium-height":181,"medium_large":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/Add-spatial-expression.png","medium_large-width":510,"medium_large-height":199,"large":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/Add-spatial-expression.png","large-width":510,"large-height":199,"1536x1536":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/Add-spatial-expression.png","1536x1536-width":510,"1536x1536-height":199,"2048x2048":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/Add-spatial-expression.png","2048x2048-width":510,"2048x2048-height":199,"card_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/Add-spatial-expression.png","card_image-width":510,"card_image-height":199,"wide_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/Add-spatial-expression.png","wide_image-width":510,"wide_image-height":199}},"image_position":"center","orientation":"horizontal","hyperlink":""},{"acf_fc_layout":"content","content":"

8. Click Add<\/strong>. The query is added to the expression with the operator and<\/strong>. This operator specifies that both criteria must be met for a census tract to be considered.<\/p>\n

All the risk areas need to be in or near the flood zones. You can use the spatial relationships in the expression builder to incorporate proximity to flood zones into the expression.<\/p>\n

9. Click Add Expression<\/strong>.<\/p>\n

10. Change the expression to Houston Census Tract Demographics<\/span>\u00a0within a distance of 0.25 Miles from HarrisCountyFloodZones<\/span>. All the returned areas will be within a quarter mile of a flood zone.<\/p>\n

11. Click Add<\/strong>.<\/p>\n

12. Change the Result layer name<\/strong> to Highest Risk<\/span> and add your initials to make the layer name unique within your organization. Make sure Use current map extent<\/strong> is checked and the full Houston city boundary is within view. Using the map extent minimizes credit usage and processing time. Click Show<\/strong>\u00a0credits<\/strong> to check the number of credits needed to run the tool.<\/p>\n

13. Click Run Analysis<\/strong>.<\/p>\n

The tool runs to find the areas with the highest risk during a flooding event. The result is a new layer added to the map. The tool may take a few minutes to run.<\/p>\n

You can now change the symbology to make it more obvious that the layer represents high risk areas.<\/p>\n

14. Click Change Style<\/strong> under the Highest Risk<\/span> layer.<\/p>\n"},{"acf_fc_layout":"image","image":{"ID":1056701,"id":1056701,"title":"change-style","filename":"change-style.png","filesize":1974,"url":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/change-style.png","link":"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-online\/analytics\/determine-flood-risk\/change-style-4","alt":"Change the style for the Highest Risk layer","author":"6771","description":"","caption":"","name":"change-style-4","status":"inherit","uploaded_to":335712,"date":"2020-11-05 15:51:12","modified":"2020-11-05 15:51:31","menu_order":0,"mime_type":"image\/png","type":"image","subtype":"png","icon":"https:\/\/www.esri.com\/arcgis-blog\/wp-includes\/images\/media\/default.png","width":356,"height":43,"sizes":{"thumbnail":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/change-style-213x43.png","thumbnail-width":213,"thumbnail-height":43,"medium":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/change-style.png","medium-width":356,"medium-height":43,"medium_large":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/change-style.png","medium_large-width":356,"medium_large-height":43,"large":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/change-style.png","large-width":356,"large-height":43,"1536x1536":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/change-style.png","1536x1536-width":356,"1536x1536-height":43,"2048x2048":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/change-style.png","2048x2048-width":356,"2048x2048-height":43,"card_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/change-style.png","card_image-width":356,"card_image-height":43,"wide_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/change-style.png","wide_image-width":356,"wide_image-height":43}},"image_position":"center","orientation":"horizontal","hyperlink":""},{"acf_fc_layout":"content","content":"

15. Under Select a drawing style<\/strong>, on the Location (Single symbol)<\/strong> card, click Options<\/strong>.<\/p>\n

16. Click the symbol to open the color options.<\/p>\n

17. Change the Fill<\/strong> and Outline<\/strong> to a dark red color and click OK<\/strong>.<\/p>\n

18. Click OK<\/strong> and Done<\/strong> to apply the changes.<\/p>\n

The Highest Risk<\/span> layer is updated to a dark red color.<\/p>\n"},{"acf_fc_layout":"image","image":{"ID":1123872,"id":1123872,"title":"HigestRisk","filename":"HigestRisk-1.png","filesize":55454,"url":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/HigestRisk-1.png","link":"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-online\/analytics\/determine-flood-risk\/higestrisk-2","alt":"Highest risk flood zones","author":"6771","description":"","caption":"","name":"higestrisk-2","status":"inherit","uploaded_to":335712,"date":"2021-01-26 16:49:25","modified":"2021-01-26 16:50:01","menu_order":0,"mime_type":"image\/png","type":"image","subtype":"png","icon":"https:\/\/www.esri.com\/arcgis-blog\/wp-includes\/images\/media\/default.png","width":600,"height":362,"sizes":{"thumbnail":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/HigestRisk-1-213x200.png","thumbnail-width":213,"thumbnail-height":200,"medium":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/HigestRisk-1.png","medium-width":433,"medium-height":261,"medium_large":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/HigestRisk-1.png","medium_large-width":600,"medium_large-height":362,"large":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/HigestRisk-1.png","large-width":600,"large-height":362,"1536x1536":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/HigestRisk-1.png","1536x1536-width":600,"1536x1536-height":362,"2048x2048":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/HigestRisk-1.png","2048x2048-width":600,"2048x2048-height":362,"card_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/HigestRisk-1.png","card_image-width":600,"card_image-height":362,"wide_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/10\/HigestRisk-1.png","wide_image-width":600,"wide_image-height":362}},"image_position":"center","orientation":"horizontal","hyperlink":""},{"acf_fc_layout":"content","content":"

Next, you\u2019ll find areas with a slightly lower risk.<\/p>\n

19. Open the Derive New Locations<\/strong> tool.<\/p>\n

20. Click Add Expression<\/strong>.<\/p>\n

The decrease in risk will be based partly on a lower number of households without vehicles. This time you\u2019ll use the range between the mean and one standard deviation above the mean in our expression.<\/p>\n

21. Change the expression to Houston Census Tract Demographics<\/span> where Owner\/Renter Households without a Vehicle (ACS 2013-2017) is between 107 and 213<\/span>.<\/p>\n

The criteria for the city boundary and the proximity to flood zones is required for all of the risk areas.<\/p>\n

22. Add the queries for the Houston city boundary and the flood zones to the expression.<\/p>\n