diff --git a/test/LowerColorado_TX_v4/domain/coastal_domain_tw.yaml b/test/LowerColorado_TX_v4/domain/coastal_domain_tw.yaml
index ca46322db..933d93bda 100644
--- a/test/LowerColorado_TX_v4/domain/coastal_domain_tw.yaml
+++ b/test/LowerColorado_TX_v4/domain/coastal_domain_tw.yaml
@@ -1,3 +1,13 @@
+##### Description #####
+# Format - 
+# Diffusive domain tailwater ID (int):
+#   headwater (int): Segment IDs identifying any headwaters of the diffusive domain. A value of '999999' indicates
+#                    to t-route that it should start at the tailwater ID and traverse upstream until a headwater or a waterbody
+#                    reached. Traversing upstream will stop at any additional IDs that are provided, essentially making them
+#                    headwaters of the diffusive domain.
+#   rfc: *outdated*
+#   rpu: *outdated*
+#######################
 
 #1 Lower Colorado River TX
 2421105: