Flood Mapping Proposal in Small Watersheds: A Case Study of the Rebollos and Miranda Ephemeral Streams (Cartagena, Spain)

Abstract

Anthropogenic landscape changes cause significant disturbances to fluvial system dynamics and such is the case of the watersheds studied near the Spanish Mediterranean coast (Cartagena). Economic growth resulted in the addition of external water resources from the Tajo River (1979) as part of the National Water Plan (1933). Irrigation water has caused the water table to rise since 1979. Furthermore, water resources have boosted urban touristic expansion, industrial estates, and road infrastructures. This study presents a diagnosis of the official flood hazard maps by applying remote sensing techniques that enable the identification of (i) areas flooded during recent events; and (ii) the possible effects of anthropogenic actions on fluvial processes affecting flooding (land use and land cover change—LULCC). The flooded areas were identified from a multispectral satellite image taken by a sensor on Sentinel-2. A multi-temporal analysis of aerial photographs (1929, 1956, 1981, 2009, and 2017) showing the fluvial and anthropic environment at a detailed scale (1:25,000) was used to define the fluvial geomorphology and the main anthropic alterations on the Rebollos ephemeral stream. Official inputs from geographical information repositories about land use were also gathered (LULC). The result was compared to the official flood hazard maps (SNCZI) and this revealed floodable areas that had not been previously mapped because official maps rely only on the hydraulic method. Finally, all the recent changes that will have increased the disastrous consequences of flooding have been detected, analyzed, and mapped for the study area.

Rainfall–runoff relationships at event scale in western Mediterranean ephemeral streams

“…Camarasa and Tilford, 2002;La Torre Torres et al, 2011;El Alfy, 2016). In addition to the topographical and climatic characteristics of the watersheds, anthropic interventions, such as irrigation, industrial uses, roads, or any water resources that change at large scale, can modify rainfall-runoff dynamics, leading to increased consequences of flooding (Conesa-García et al, 2016;Betancourt-Suárez et al, 2021). Most of the previous works based on rainfall-runoff modelling in ephemeral streams were dedicated to runoff forecasting based on rainfall and topographical characteristics at different temporal and spatial scales.…”

“…This means that the return periods could be higher because the degree of reliability provided by the model only considers the situation in which those variables occur in a RE of average duration (1.9 and 2.1 d, respectively). In this regard, further investigation is needed to set more accurate return periods because univariate approaches might lead to inadequate estimation of the risk of a RE (Brunner et al, 2016). It should also be considered that we only used the data of the RE in periods when flow was available (18 years for Algeciras and 25 years for Upper Mula) because hourly maximums were not available outside of the considered periods, meaning that the obtained return periods could be lower if long-term data series were included.…”

Meandering rivers’ morphological changes analysis and prediction – a case study of Barak river, Assam

“…Spatial analytic technologies such as geographic information systems (GIS) and remote sensing (RS) can be used efficiently for the accurate identification of flood extent and depths within flood plains, which are crucial for proper flood management (Sahoo & Pekkat 2018). Many remote sensing studies were done on major rivers worldwide (Rinaldi 2003;Yang et al 1999;Kummu et al 2008;Surian et al 2009;Betancourt-Suárez et al 2021). Therefore, it is revealed from the previous literature that one of the key reasons for bank erosion is the occurrence of high floods in the alluvial channel (Lane et al 1995).…”

Urban Flood Loss Estimation and Evacuation Design Based on a 500-Year Extreme Flood Event in Syracuse City

“…Floods can cause massive negative impacts on human beings and their living environments, such as the loss of human lives and economic value, destruction of the infrastructure, land and soil degradation, crop and vegetation damage, and the submergence of cities [1,2]. Urbanization has increased the frequency and magnitude of floods and reduced the permeability of the ground surface, encouraging flash floods even for regular rainfall events [3].…”

“…Some of them, such as simple empirical models, economic models, Input-Output 2 of 22 models, and computational general equilibrium (CGE) models have been widely used to characterize the damage estimation process [12]. These models are based on the same definition of flood damage: Flood damage = Exposed objects × Damage curve (or function) (1) In this equation, the exposed objects during a specific flood event may be represented by the inundation characteristics, which can be obtained from the modeling results [13]. These characteristics could be flood extent, depth, or velocity, depending on the specifically used damage curve (or function), which is usually obtained from hydraulic modeling analyses for the selected study area.…”