Flood hazard delineation combining geomorphological and hydrological methods: an example in the Northern Iberian Peninsula

Abstract

Flood mapping requires the combination and integration of geomorphological and hydrological-hydraulic methods; however, despite this, there is very little scientific literature that compares and validates both methods. Two types of analysis are addressed in the present article. On the one hand, maps of flood plains have been elaborated using geomorphological evidence and historical flood data in the mountainous area of northwestern Spain, covering an area of more then 232 km 2 of floodplains. On the other hand, a hydrometeorological model has been developed (Clark semidistributed unit hydrograph) in the Sarria River basin (155 km 2 , NW Spain). This basin is not gauged, hence the model was subjected to a goodness-of-fit test of its parameter (curve number) by means of Monte Carlo simulation. The peak flows obtained by means of the hydrological model were used for hydraulic modeling (one-phase, one-dimensional and steady flow) in a 4 km 2 urban stretch of the river bed. The delineation of surface areas affected by floods since 1918, as well as those analyzed subsequent to the geomorphological study, reveals a high degree of reliability in the delineation of the flooded areas with frequent recurrence intervals (\50 years). If we compare these flooded surface areas with the estimate obtained by the hydrological-hydraulic method we can see that the latter method overestimates the extent of the surface water by 144% for very frequent recurrence intervals ([10 years) and underestimates it as the recurrence interval increases, by up to 80% less floodplain for

Flood Hazard and Risk Assessment in Chamoli District, Uttarakhand Using Satellite Remote Sensing and GIS Techniques

“…Flood risk mapping is often the first step for flood risk management [36], and it provides data required for urban planning, wildlife habitat modelling and management, design for infrastructure, flood mitigation and response. Flood hazard and risk assessment yields risk maps, which can be created using GIS based hydrological observations of the frequency, magnitude and duration of flood events, as well as DEMs that characterize the topographic basin within which flood events occur [37] [38]. Flood risk maps can be used to identify the weaknesses in a flood defense system and the patterns of vulnerability of human infrastructure and wildlife habitat.…”

Flood risk assessment and mapping in peri-urban Mediterranean environments using hydrogeomorphology. Application to ephemeral streams in the Valencia region (eastern Spain)

“…The hydrogeomorphological method has proved to be extremely efficient in interpreting flood processes in this type of intermittentflowing, highly torrential basin in which standard hydrolological and hydraulic models prove inadequate (Ballais et al, 2005;Diakakis, 2011;Díez-Herrero et al, 2008;Guzzetti et al, 2005;Lastra et al, 2008;Ortega & Garzón, 2009 ). This method enables analysis with scarce hydrological data and is highly flexible as any change in the floodable area's morphology (whether natural or human-induced) can be included in a hydrogeomorphological map and be easily assessed in hazard terms.…”

“…Generally speaking, three main methodologies can be established: historical and paleohydrological methods (Baker, Kochel, & Patton, 1988;Benito et al, 2004), hydrogeomorphological methods, and hydrological-hydraulic methods (Lastra, Fernández, Díez-Herrero, & Marquínez, 2008). These could be added to with the recent appearance of dendrogeomorphological methods .…”

“…Although it is not a quantitative approach, it provides a reliable representation of the processes, it is economical, and in 80% of the cases enables decision-making (Marco, 2006). Applications in Mediterranean areas in the south of France (Ballais et al, 2005;Chave, 2002), Italy (Guzzetti & Tonelli, 2004;Guzzetti, Stark, & Salvati, 2005), and northwestern Spain (Lastra et al, 2008) have shown the effectiveness of the method in torrential basins with changing morphology and large-scale erosion potential in which hydrological information is scarce or non-existent. In this paper, hazard mapping is based on the interpretation and analysis of the floodplain's geomorphology, in terms of hazards.…”

Flood Risk Zoning of Satluj River Basin, Himachal Pradesh, India

“…There are several methods for flood risk mapping, primarily based on hydrological, meteorological and geomorphological approaches. Particularly, in mountainous region where hydro-meteorological data are commonly insufficient and sparsely available and restricted to generate flood risk models, the geomorphologic method demonstrated its effectiveness and appropriateness (Wolman, 1971;Lastra et al, 2008). This method implies interpretation of satellite imageries and field investigation of flood evidences to study geomorphologic characteristics in relationship with historical or future flood events.…”