Cosmogenic radionuclides (CRNs) measured in river sediment are widely used to estimate catchment-averaged erosion rates. These estimates typically rely on assumptions of steady-state erosion and minimal sediment storage, which can break down where the landscape has recently been perturbed due to tectonics or climate. In many settings, erosion is often highly variable in space and time, and sediment delivered to the channel may have complex residence and exposure histories. Sediment can be stored temporarily, reworked multiple times, or delivered in pulses following mass-wasting events, which can dilute the CRN signal with low-concentration material from depth. Although short-term effects of events like landslides on CRN concentrations are known, it remains difficult to assess how repeated disturbances and a change in erosion rates can influence the CRN signal over longer timescales. In this study, we develop a numerical model to simulate how transient erosion affect the CRN concentrations of ¹⁰Be, ²⁶Al, and ¹⁴C in detrital sediment by using the 2016 Kaikōura earthquake in New Zealand as a case study. This work aims to identify the most robust strategies for sampling detrital sediment in dynamic landscapes, helping researchers decide how to collect samples that best reflect meaningful erosion rates.