Streams in the Illawarra region of New South Wales have dynamic hydro-geomorphic characteristics that are atypical of the broader Sydney Basin. These characteristics include: small, steep catchments subject to intense rainfall events that are capable of generating flood discharges comparable to world maximum rainfall-runoff events; high energy escarpment channels that debouch bedload sediment fans and bars onto a low energy coastal plain; well developed macro-channels that convey high magnitude flows through the middle catchment zone; rapid and prolific vegetation growth and downstream decreasing channel capacities within the lower catchment depositional zone. This paper outlines local examples of the dynamic interactions between flood hydrology, hydraulics and geomorphology of Illawarra streams. Appropriate planning to account for their dynamic nature is particularly important in the context of catchment management for Lake Illawarra as some 10,000 - 20,000 new dwellings are planned for future development in areas currently dominated by rural land uses.