As far as I know there is no way on google maps or open street maps to determine what the soil type is in any particular area, you would need a geologic map (e.g. this one)for that, and even then it is only going to give you a suggestion as to what it is as geologic maps are usually concerned with rock types, though they can also cover sedimentary deposits such as clays and alluvial deposits.
Clay in particular is a problem for pooling water as they are very fine sediment which is fairly water-impermeable, making it hard for water to drain away. Clays are often, but definitely not always found in river valleys and similar situations.
You can however interpret some things from google maps if you turn on the contours and/or satellite images. With the contours - the closer they are together, the steeper the terrain, and the less likely it will be that you have water depositing on the surface. However, this can also mean that an flattish area (such as you might want to camp on) in the middle of a steep one might pool water.
The satellite images can tell you what sort of cover to expect - trees, bushes, grass. Sometimes vegetation can give you an indication of what is lying below the surface - for instance swamp cypress almost always grow near water in flat lands - so you would want to avoid those, whereas pines tend to prefer steeper terrain.