Copious rainfall and high temperatures combine to keep chemical processes continuous on the rocks and soils. Leaching of all soluble elements of the deeply decayed rock produces Ultisols and Oxisols that are often especially rich in hydroxides of iron, magnesium, and aluminum. Streamflow is fairly constant because a large water surplus throughout the year provides ample runoff. River channels are lined with dense vegetation. Sand bars and banks are less conspicuous than in drier regions.
Floodplains have meanders and many swampy sloughs where river channels have shifted their courses.
Although water is abundant, river systems carry relatively little dissolved material, because thorough leaching of soils removes most soluble mineral matter before it reaches streams. Not all equatorial rainforest areas have low topographic relief.