Answer: <em>Mean sea level is an average level of the surface of one or more of Earth's bodies of water from which heights such as elevation may be measured.</em>
Not quite sure what you're asking, but erosion and deposition do create land forms. For example: erosion along the coastline may result in the formations of arches, stacks, stumps, wave cut platforms, caves, etc. Deposition, different amount of it and in certain areas, under the influence of either destructive or constructive waves, will form beaches - ones with a lot of beach, through a lot of deposition, or slopes beaches where destructive waves have crashed upon the beach. Hope this is what you're looking for.
Vegetation catches precipitation on its leaves, slowing it down or holding it for a while. This gives the ground more time to absorb the water, so there's less runoff.
