Comparing a Large‐scale Dem‐based Floodplain Delineation Algorithm With Standard Flood Maps: The Tiber River Basin Case Study

Morrison

Annis

et al. 2018

River Research & Apps

Self Cite

Hydrogeomorphic approaches for floodplain modelling are valuable tools for water resource and flood hazard management and mapping, especially as the global availability and accuracy of terrain data increases. Digital terrain models implicitly contain information about floodplain landscape morphology that was produced by hydrologic processes over long time periods, as well as recent anthropogenic modifications to floodplain features and processes. The increased availability of terrain data and distributed hydrologic datasets provide an opportunity to develop hydrogeomorphic floodplain delineation models that can quickly be applied at large spatial scales. This research investigates the performance of a hydrogeomorphic floodplain model in two large urbanized and gauged river basins in the United States, the Susquehanna and the Wabash basins. The models were calibrated by a hydrologic data scaling technique, implemented through regression analyses of USGS peak flow data to estimate floodplain flow levels across multiple spatial scales. Floodplain model performance was assessed through comparison with 100-year Federal Emergency Management Agency flood hazard maps. Results show that the hydrogeomorphic floodplain maps are generally consistent with standard flood maps, even when significantly and systematically varying scaling parameters within physically feasible ranges, with major differences that are likely due to infrastructure (levees, bridges, etc.) in highly urbanized areas and other locations where the geomorphic signature of fluvial processes has been altered. This study demonstrates the value of geomorphic information for large-scale floodplain mapping and the potential use of hydrogeomorphic models for evaluating human-made impacts to floodplain ecosystems and patterns of disconnectivity in urbanized catchments.

Section: Discussionmentioning

confidence: 99%

Hydrologic scaling for hydrogeomorphic floodplain mapping: Insights into human‐induced floodplain disconnectivity

Morrison

Annis

et al. 2018

River Research & Apps

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“…The increasing frequency and unusual spatial distribution of local inundation events in the urban area of Rome, happening always more often in the uphill of the small tributaries of the Tiber river basin, is certainly related to the impact of urbanization. In the last decades, urban development processes in the area of Rome have completely transformed the majority of the flood plains (Nardi et al, 2013;Manfreda et al, 2014). It is easy to observe, using aerial photos or land use layers, the impact of river-road intersections along major channels in the downstream regions towards the confluence with the major Tiber and Aniene river systems (Figure 1).…”

Section: Introductionmentioning

confidence: 99%

On the impact of urbanization on flood hydrology of small ungauged basins: the case study of the Tiber river tributary network within the city of Rome

J Flood Risk Management

Annis

Biscarini

2015

The small ungauged basins of the highly urbanized area of the city of Rome are often the subject of critical flood conditions for the significant human‐made transformations. In this work the EBA4SUB framework, implementing the hydrogeomorphic width function instantaneous unit hydrograph rainfall run‐off model, and using digital elevation model, land use and synthetic precipitation as main input information, is applied for evaluating extreme hydrologic forcing conditions at the basic scale. The goal is to understand the rationale behind the observed increasing frequency of local urban inundations that are also observed in the uplands. Results present the impact of urbanization expressed by both the run‐off coefficient, the artificial drainage, impacted by paved surfaces and a dramatic number of river–road intersections (i.e. culverts), and the upstream to downstream non‐natural scaling behaviour of hydrologic parameters and in particular the peak discharge per unit drainage area.

“…This hydrogeomorphic technique has been demonstrated in previous studies (e.g., Nardi et al. ; Rathjens et al. ), and it assumes that floodplain configurations, which can be identified within topographic data, are the product of natural erosion and deposition occurring over large time spans.…”

Section: Methodsmentioning

confidence: 99%

Spatial Relationships of Levees and Wetland Systems within Floodplains of the Wabash Basin, USA

Morrison

Bray

J American Water Resour Assoc

et al. 2018

Self Cite

Given the unique biogeochemical, physical, and hydrologic services provided by floodplain wetlands, proper management of river systems should include an understanding of how floodplain modifications influence wetland ecosystems. The construction of levees can reduce river–floodplain connectivity, yet it is unclear how levees affect wetlands within floodplains, let alone the cumulative impacts within an entire watershed. This paper explores spatial relationships between levee and floodplain wetland systems in the Wabash Basin, United States. We used a hydrogeomorphic floodplain delineation technique to map floodplain extents and identify wetlands that may be hydrologically connected to river networks. We then spatially examined the relationship between levee presence, wetland area, and other river network attributes within discrete subbasins. Our results show that cumulative wetland area is relatively constant in subbasins that contain levees, regardless of maximum stream order within the subbasin. In subbasins that do not contain levees, cumulative wetland area increases with maximum stream order. However, we found that wetland distributions around levees can be complex, and further studies on the influence of levees on wetland habitat may need to consider finer resolution spatial scales.