e20xx, e19xx, series model is build as simple as possible, still powerful (e stands for ESRI based map )
California Flood MapOfficial california flood map is here. https://gis.bam.water.ca.gov/bam/
Now you can view these layers with this new model e1999https://transparentgov.net/json2tree/arcgis/js4/featurelayer_tree_multi.html?layer_id=-99999&layer=am_viewer&url=https%3A%2F%2Fgis.water.ca.gov%2Farcgis%2Frest%2Fservices%2FBoundaries%2Fbam_viewer%2FMapServer&_center_zoom=16&_center_lat=34.049039&_center_long=-118.246521&selectedItemIdArray=12%2C13%2C14%2C15%2C16
https://transparentgov.net/json2tree/esri/server2/folder.html?org=https%3A%2F%2Fgis.water.ca.gov%2Farcgis%2Frest%2Fservices&url=https%3A%2F%2Fgis.water.ca.gov%2Farcgis%2Frest%2Fservices&arcgis_online_token=&select_folder=467&select_layer=-1
Los angeles NavigateLAmodel e1999 allow you select multiple layers
https://transparentgov.net/json2tree/arcgis/js4/featurelayer_tree_multi.html?layer_id=-99999&layer=NavigateLA&url=https%3A%2F%2Fmaps.lacity.org%2Farcgis%2Frest%2Fservices%2FMapping%2FNavigateLA%2FMapServer&_center_zoom=11&_center_lat=34.02106886643995&_center_long=-118.41176680763678&selectedItemIdArray=93%2C94%2C95%2C96%2C97%2C98%2C348%2C349%2C381%2C412
https://transparentgov.net/json2tree/arcgis/js4/featurelayer_tree_multi.html?layer_id=-99999&layer=NavigateLA&url=https%3A%2F%2Fmaps.lacity.org%2Farcgis%2Frest%2Fservices%2FMapping%2FNavigateLA%2FMapServer&_center_zoom=15&_center_lat=34.05770522547549&_center_long=-118.45223231403577&selectedItemIdArray=93%2C94%2C95%2C96%2C97%2C98%2C341%2C342%2C343%2C344%2C345%2C348
https://transparentgov.net/json2tree/esri/server2/folder.html?url=https%3A%2F%2Fmaps.lacity.org%2Farcgis%2Frest%2Fservices&org=Los+Angeles+CA+Public+Works+NavigateLA&_center_lat=34.049039&_center_long=-118.246521&_center_zoom=17&cross=default&timeout=3000&arcgis_online_token=&select_folder=19&select_layer=-1