Why do I have red dirt seeping over my deck in rain?

It's probably just flooding it and it's pushing it up thru boards or from around the sides of pool deck.The hard rain doesn't give it time to soak thru.,may have a plastic liner under red dirt also so the water when it rains hard can only rise. Red dirt you live in high desert area? where?New Mex.,OK,AZ,TX or was it brought in as fill dirt.Red dirt is clay based & if it is compacted real tight it will not absorb water.That's why many ares that have this soil along with fast heavy rains=flash floods & It stains everything red tinted. Not sure what to tell you to do. Make drainage tunnels under pool deck then add french drains so water has somewhere to go.Landscape fabric over dirt under decking would have helped at install. https://www.thebalancesmb.com/expert-tips-on-how-to-install-a-french-drain-drain-tile-845026

Hi Jan,

It could be all the residue dust is pulled up into the air and then drops with the rain? A bit of a bind but maybe use something heavier to much with...........

Remove the deck and incestigate.

It's coming up from under decking(is it wood or composite w/spaces between boards?) or around the sides & pooling on deck. Red dirt is clay based doesn't absorb water. The dirt under deck has been compacted making it even worse and deck doesn't have any underlay to keep water with dirt from coming back up either thru decking or up and around the sides. Only solution would be to dig trenches under deck and add french pipes to provide proper drainage. Red dirt stains everything are you in OK,TX,AZ or New Mex.,probably need pressure washer to get it off if you even can. Areas with this red dirt/clay are prone to flash flooding which is basically what is happening around your pool/deck area, & even if no dirt actually gets on deck areas the water will still be red and stain it.