{"id":1670132,"date":"2022-07-28T12:47:41","date_gmt":"2022-07-28T19:47:41","guid":{"rendered":"https:\/\/www.esri.com\/arcgis-blog\/?post_type=blog&p=1670132"},"modified":"2022-07-28T14:47:44","modified_gmt":"2022-07-28T21:47:44","slug":"hydro-flattening-of-river-shorelines-in-lidar-based-dem-production","status":"publish","type":"blog","link":"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-pro\/3d-gis\/hydro-flattening-of-river-shorelines-in-lidar-based-dem-production","title":{"rendered":"Hydro-Flattening of River Shorelines in Lidar Based DEM Production"},"author":315862,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","format":"standard","meta":{"_acf_changed":false,"_searchwp_excluded":""},"categories":[23771,22941,22771],"tags":[766522,766532,24131,766512,24381],"industry":[],"product":[36561],"class_list":["post-1670132","blog","type-blog","status-publish","format-standard","hentry","category-3d-gis","category-mapping","category-natural-resources","tag-breaklines","tag-constraints","tag-dem","tag-hydro-flattening","tag-lidar","product-arcgis-pro"],"acf":{"authors":[{"ID":315862,"user_firstname":"Clayton","user_lastname":"Crawford","nickname":"Clayton","user_nicename":"ccrawford","display_name":"Clayton Crawford","user_email":"ccrawford@esri.com","user_url":"","user_registered":"2022-07-27 17:22:19","user_description":"Clayton Crawford is Product Owner and Senior Product Engineer for the ArcGIS 3D Analyst extension. He specializes in lidar processing and TIN based surface modeling.","user_avatar":""}],"short_description":"Discusses a new geoprocessing tool, Enforce River Monotonicity, and how it's used in a workflow to create hydro-flattened DEMs from Lidar.","flexible_content":[{"acf_fc_layout":"content","content":"

One of the tricky aspects of DEM production from lidar is related to the representation of water. It\u2019s desirable for lakes and reservoirs to be flat, and for larger rivers to be level from bank to bank while also only flowing downward, never up. The enforcement of this behavior is commonly referred to as \u2018hydro-flattening\u2019. It\u2019s done for cartographic, or aesthetic, purposes. Hillshades and contours, for example, will look and behave as expected when made from DEMs that have been properly hydro-flattened. Lakes and reservoirs are relatively easy to handle because they just get completely flattened. Rivers are where the greater challenge lies because they need to flow downslope, naturally following the surrounding terrain.<\/p>\n"},{"acf_fc_layout":"image","image":{"ID":1670472,"id":1670472,"title":"dem_hydro_flattening_combined_1024","filename":"dem_hydro_flattening_combined_1024.png","filesize":1056902,"url":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2022\/07\/dem_hydro_flattening_combined_1024.png","link":"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-pro\/3d-gis\/hydro-flattening-of-river-shorelines-in-lidar-based-dem-production\/dem_hydro_flattening_combined_1024","alt":"","author":"315862","description":"","caption":"","name":"dem_hydro_flattening_combined_1024","status":"inherit","uploaded_to":1670132,"date":"2022-07-27 19:24:03","modified":"2022-07-27 19:24:03","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":1023,"height":467,"sizes":{"thumbnail":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2022\/07\/dem_hydro_flattening_combined_1024-213x200.png","thumbnail-width":213,"thumbnail-height":200,"medium":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2022\/07\/dem_hydro_flattening_combined_1024.png","medium-width":464,"medium-height":212,"medium_large":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2022\/07\/dem_hydro_flattening_combined_1024.png","medium_large-width":768,"medium_large-height":351,"large":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2022\/07\/dem_hydro_flattening_combined_1024.png","large-width":1023,"large-height":467,"1536x1536":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2022\/07\/dem_hydro_flattening_combined_1024.png","1536x1536-width":1023,"1536x1536-height":467,"2048x2048":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2022\/07\/dem_hydro_flattening_combined_1024.png","2048x2048-width":1023,"2048x2048-height":467,"card_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2022\/07\/dem_hydro_flattening_combined_1024-826x377.png","card_image-width":826,"card_image-height":377,"wide_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2022\/07\/dem_hydro_flattening_combined_1024.png","wide_image-width":1023,"wide_image-height":467}},"image_position":"center","orientation":"horizontal","hyperlink":""},{"acf_fc_layout":"content","content":"

Color hillshade and contours made from untreated DEM on left, results from hydro-flattened DEM on right.<\/em><\/p>\n"},{"acf_fc_layout":"content","content":"

In ArcGIS Pro 3.0, the 3D Analyst extension introduces a new geoprocessing tool that facilitates hydro-flattening of river shorelines. It\u2019s called Enforce River Monotonicity<\/strong><\/a>. It ensures river heights, usually obtained from lidar, always go in one direction (i.e., down) which is why the word \u2018monotonicity\u2019 is used; it\u2019s uni-directional in Z. It also ensures the bank-to-bank height is consistent. The tool is a key piece of a larger workflow to make high quality DEMs.<\/p>\n"},{"acf_fc_layout":"content","content":"

General workflow for creating hydro-flattened DEMs from aerial lidar data using a LAS dataset<\/a>:<\/p>\n

    \n
  1. Obtain 2D polygons that represent larger rivers.<\/strong> For this workflow, larger rivers are those which average 30 meters or more in width. Sources for these polygons are varied. They can come from classified multi-spectral imagery (best captured at same time as lidar) or from previously compiled map data. For example, in the United States, there\u2019s the National Hydrography Dataset, specifically NHDPlus HR<\/a>. Water body polygons are usually represented as 2D features. These 2D features will be used to create 3D features.<\/li>\n
  2. Classify ground points.<\/strong>\n