These effects can be additive and interactive in a variety of ways. Complex spatial and temporal relationships also exist.
Cumulative change can occur in ecosystems such as watersheds.
Effects within smaller watershed areas fall within many categories from sedimentation to dredging and organic debris distribution. Hydrologic effects and sedimentation from land disturbance are interrelated. Biological ramifications are dependant on watershed size, because there can be linear increases in fish species as stream order increases and there are numerous strong relationships among biological measures and stream size. Within watersheds, hydropower development can have cumulative effects. Ecological effects vary with flow fluctuations and channel morphology.