Abstract
The amount of discharge in a river section is a key uncertainty factor in flood risk analyses and is determined
by upstream conditions as well as the distribution of discharge over river branches at river bifurcations. This
study assesses the impact of river interventions in a bifurcating river system, considering the Dutch river Rhine
system with its two bifurcation points. The river system is schematized in a 1D model, using the main channel roughness and floodplain roughness as stochastic variables. With this model we evaluated the uncertain
impact of river interventions with varying locations and dimensions. Model results show self-regulation of
downstream water levels and water level uncertainties through changes in the discharge distribution at bifurcation points. This is explained by a self-regulating mechanism in which the water level lowering impact of an
river intervention induces an increase in discharge towards the branch in which the river intervention was implemented. This effectively reduces the impact of the intervention. Additionally, the self-regulating mechanism
reduces the uncertainty of the impact of the river intervention. So, compared to a non-bifurcating river system,
the impact of river interventions on flood water levels reduces, but involves less uncertainty. Furthermore, results show that the self-regulating mechanism has a larger influence in the smaller distributaries compared to
the larger distributaries. Considering the results, it is essential to regard the entire river system, and specifically
the influence on the distribution of discharge at bifurcation points, in the design and assessment of river interventions. We conclude that in a bifurcating river system, water levels and their uncertainties are controlled by
a self-regulating mechanism. Water level uncertainties are smaller and therefore, flood risk estimates are more
certain if considering this self-regulating mechanism in flood risk analyses.
by upstream conditions as well as the distribution of discharge over river branches at river bifurcations. This
study assesses the impact of river interventions in a bifurcating river system, considering the Dutch river Rhine
system with its two bifurcation points. The river system is schematized in a 1D model, using the main channel roughness and floodplain roughness as stochastic variables. With this model we evaluated the uncertain
impact of river interventions with varying locations and dimensions. Model results show self-regulation of
downstream water levels and water level uncertainties through changes in the discharge distribution at bifurcation points. This is explained by a self-regulating mechanism in which the water level lowering impact of an
river intervention induces an increase in discharge towards the branch in which the river intervention was implemented. This effectively reduces the impact of the intervention. Additionally, the self-regulating mechanism
reduces the uncertainty of the impact of the river intervention. So, compared to a non-bifurcating river system,
the impact of river interventions on flood water levels reduces, but involves less uncertainty. Furthermore, results show that the self-regulating mechanism has a larger influence in the smaller distributaries compared to
the larger distributaries. Considering the results, it is essential to regard the entire river system, and specifically
the influence on the distribution of discharge at bifurcation points, in the design and assessment of river interventions. We conclude that in a bifurcating river system, water levels and their uncertainties are controlled by
a self-regulating mechanism. Water level uncertainties are smaller and therefore, flood risk estimates are more
certain if considering this self-regulating mechanism in flood risk analyses.
| Original language | English |
|---|---|
| Pages | 43 |
| Number of pages | 1 |
| Publication status | Published - 10 Aug 2021 |
| Event | 8th International Conference on Flood Management 2021: Lowering Risk by Increasing Resilience - Virtual Event, Iowa City, United States Duration: 9 Aug 2021 → 11 Aug 2021 Conference number: 8 |
Conference
| Conference | 8th International Conference on Flood Management 2021 |
|---|---|
| Abbreviated title | ICFM8 |
| Country/Territory | United States |
| City | Iowa City |
| Period | 9/08/21 → 11/08/21 |