The use of a system of detention reservoirs distributed across a region has been gaining interest as an innovative way to manage riverine flooding. An open problem is the role played by the spatial configuration of detention projects in regulating the flow. Possible locations for reservoirs within a watershed are numerous, however methods used in literature to place reservoirs on real watersheds and couple them with realistic values of storage are not very detailed.
This thesis presents a methodology for modeling dams and related reservoirs at high density, based on the analysis of a Digital Elevation Model (DEM) of the terrain, and extracting their geometric characteristics. Four indicators, based on the morphology of reservoirs and their position in the network, are proposed to classify them and identify which locations are more suitable for a detention project. These are the Horton order, the ratio between volume and extent of the reservoir, the ratio between volume and the expected inflow volume, and the volume itself.
The study area of the analysis is the Turkey River watershed, in northeastern Iowa. The algorithm analyzed over 100,000 locations and successfully modeled more than 60%. Most of the failed attempts occurred in a region of the watershed where the terrain is generally flat and reservoirs, when feasible, tend to store water inundating a large area. Regional patterns of ratios are highlighted at the scale of the watershed, but no clear, recurring pattern is identified at the subwatershed level.
The considered indicators have the purpose of narrowing down locations to a manageable number of candidates. Further criteria can also be adopted, based on land use and social and economic considerations. Selected reservoirs can be variously combined and entered, together with their geometric characteristics, in hydrological models and optimization processes to determine the best spatial configuration possible.