Flood retention lakes in a rural-urban catchment: how can they be better
used for flood mitigation?
Abstract
Flood retention lakes (RLs) are widely employed in rural-urban
catchments with low impacts on the natural environment. While hydrologic
models have been commonly applied to evaluate RLs’ performances,
insights are lacking over the consequences of a wide climatic
variability, particularly those corroborated by 2D hydrodynamic models.
Thus, this study aims to conduct a systematic catchment-scale evaluation
of RL effectiveness; blueprinted RLs with various geographic
configurations are also considered in addition to the individual RL. A
2D hydrodynamic model is verified to be capable of simulating flood
events in the rural-urban catchment interacted with RLs. Under a wide
range (1- to 15- hour duration and 1- to 100-year return period) of
rainstorm scenarios, the RL has a satisfactory performance within an
L-shaped band in the frequency-duration diagram. The L-shaped band
coincides with moderate return periods (10- to 25- year) and large
durations (> 6 hours) or small durations (< 4
hours) and large return periods (> 25-year), whereas
different criteria yield different optimal combinations. With the
increase of event size, 4 typical stages of RL-river interactions are
characterized, which projects the catchment-scale performances.
Blueprinted RLs with distributed and parallel connections mitigate
larger areas of inundation in sub-watersheds than aggregated and series
ones. Upstream controls are less effective than downstream controls
under moderate events while the relation is reversed for extreme events.
Critical changing factors concerning RL-river interactions and
spatiotemporal rainstorm variabilities prompt comprehensive
considerations of both local-scale RL configurations and catchment-scale
climate characterizations.