When connectivity helps and when it hurts: How natural vs. human-induced connectivity affect flood wave attenuation and land change

Geomorphic transitions—such as the interface between rivers and floodplains—are critical zones controlling water, sediment, and nutrient transport. River–floodplain connectivity often occurs through secondary channels that convey fluxes into the floodplain. In other cases, connectivity is created or amplified by human interventions. But is higher connectivity in a landscape always beneficial?

In this talk, we examine the role of connectivity—both structural and functional—in shaping flood wave attenuation and long-term land change. We draw on two contrasting landscapes. First, in the Trinity River (Texas), rivers and floodplains are connected via floodplain channels. Using an idealized model, we show that attenuation transitions from connectivity-limited to storage-limited as discharge increases. Secondary channel conveyance promotes early floodplain inundation and attenuation at lower flows, but at higher flows it can fill storage rapidly and even increase downstream flood peaks. Greater conveyance and wider floodplains increase fluxes to the floodplain, yet conveyance shortens residence times while wider floodplains prolong them.

Second, we examine coastal Louisiana: the sediment-rich Wax Lake Delta, which is gaining land, and the sediment-starved Terrebonne Bay, which is losing land. Here, connectivity plays opposite roles—enhancing resilience and land growth in one system while accelerating degradation in the other.

This work shows that connectivity is not universally “good”: it can attenuate floods and build land under some conditions, but under others it transfers risk or drives loss. Understanding these dynamics is critical for designing floodplain reconnection and managing landscapes under climate change.