Delta

A fan-shaped or branching formation of sediment deposited where a river meets standing water (sea or lake) and loses the energy to carry its sediment load further — diagnostic feature is the braided, multi-channel pattern splitting the river into several distributaries, actively building new land out into the water rather than being shaped by tides.

Wetland / Marsh / Fen

Braided, multi-channel river mouth building new land into marshland and open water.

Temperate

Setting: Coastal

Candidate: The Mississippi River Delta, Louisiana — unverified, for your own research and confirmation before use.

Retagged from an earlier, wrong Continental label — Louisiana’s Gulf Coast climate is humid subtropical, closer to the opposite of continental (mild, maritime-moderated, not large seasonal swings). Same recurring climate-tagging tension as Cloudland Canyon and the Mississippi Delta floodplain, now a third time — tagged Temperate for lack of a better bucket, same call made there.

Arid

Setting: Coastal

Candidate: The Volga Delta, Astrakhan Oblast, Russia — unverified, for your own research and confirmation before use.

Largest delta in Europe, draining into the Caspian — technically a closed inland basin (the world’s largest lake, whatever it’s locally called), worth flagging against this landform’s own 'sea or lake' framing as a genuine edge case, not a mismatch. Explicitly documented as arid climate, a real contrast to the Mississippi variant. Diagnostic features: linear 'Baer’s mounds' unique to this delta, and what’s reported as the largest lotus field on Earth, roughly 3 km by 15 km, in bloom July-September.

Arctic / Subarctic

Setting: Coastal

Candidate: The Lena Delta, Sakha Republic, Russia — unverified, for your own research and confirmation before use.

A genuine, textbook delta — unlike the Ob and Yenisei further west, which discharge into large gulfs rather than branching (see Estuary, not here). Largest delta in the Arctic at roughly 32,000 sq km, splitting into hundreds of channels described as resembling the branching pattern of a tree; hundreds of small tundra lakes dot the flat delta plain between them. Largest protected wilderness area in Russia; mammoth tusks have been recovered from the delta sediments.