Final answer:
The runoff in a forest area would increase and become more erosive if all the trees were cut down, leading to greater erosion, more frequent and severe flooding, and higher sediment discharge into aquatic systems.
Step-by-step explanation:
If all the trees were cut down in a forest area, the runoff would change significantly. Without the trees, there would be a lack of vegetation to intercept raindrops and promote soil development, which means the rain would directly hit the soil surface, increasing the likelihood of erosion and flood events.
Tree roots, which act to hold the soil together and prevent it from being washed away, would no longer be present to perform this vital function. Additionally, the loss of tree cover could lead to increased soil compaction and changes in drainage patterns, potentially exacerbating flooding issues.
The impact of these changes on runoff would likely result in an increased discharge of sediment into oceans, affecting coral reefs and other aquatic systems.