VENERO CLARO TEST SITE (SPAIN)

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1 VENERO CLARO TEST SITE (SPAIN) Location The Arroyo Cabrera is a torrential stream, tributary of the Alberche River in the Tagus Basin (Central Iberian Peninsula). It is formed from the confluence of several streams on the northern slopes of the Sierra del Valle in the Gredos mountain range of the Spanish Central System (Figure 1). Coordinates of the test site (Area of interest) Geographic Latitude/Longitude X/Y UTM (zone 30 N) N 40º S 40º W - 4º E - 4º Figure 1. Location of the hydrographic basin of the Alberche River and the Cabrera stream watershed.

It is formed from the confluence of several streams on the northern slopes of the Sierra del Valle in the Gredos mountain range of the Spanish Central

2 Geological, climatological & topographical conditions Bedrock consists of Upper Paleozoic granitoids and superficial Quaternary formations, made up of conglomerates, gravels, sands and silts. These cover the slopes, the floor of the valley and depressions known as navas. The soils are fundamentally entisols developed on weathered profiles of granitic materials, fluvisols and inceptisols. The climate of the study area is Mediterranean Continental, which is typical of the Spanish medium mountain ranges. The average annual temperature is 14.6ºC, with an average minimum of 6.3ºC in January, the coldest month, and an average maximum of 24.8ºC in July, the hottest month. Average annual rainfall is 414 mm. November is the month when most rain falls, with an average of mm. The month with the lowest rainfall is August, with only 9.50 mm. The vegetation is made up of 43% Pinus pinaster, 40% Provence broom (Cytisus oromediterraneus), and, to a lesser extent, Quercus pyrenaica, Pinus sylvestris and Alnus glutinosa. The area covered by the stream's catchment is approximately 15.5 km 2 and has a subtriangular shape (Fig. 1). The maximum height difference within the basin is 1188 m and the length of the main channel is 5500 m, with an average slope of 21.6%. Several factors determine frequent flash floods in the Arroyo Cabrera basin. First, the headwater has average slopes of 50%, although in some channel hillsides these ones can reach 100%. As a consequence, threshold runoff and time of concentration of the basin are decreased. Furthermore, 21.6% is the average slope of the main channel which makes possible a fast flood wave routing almost without lamination. Other factors responsible for the torrential behaviour of this basin are its high drainage density, due to the almost circular morphology of its headwater, and small area (15.5 km 2 ).

The climate of the study area is Mediterranean Continental, which is typical of the Spanish medium mountain ranges. The average annual temperature is 14.6ºC, with an average minimum of 6.

3 Ongoing monitoring The hydrological monitoring of the basin consists of six rain gauges (Hobo Rain Collector, Davis Instruments) located homogenously in the basin in order to record properly the orographic component of precipitation. Two flow gauges (WL16 Level Water, Global Water) are also installed in two control sections of the Arroyo Cabrera where a concrete-bed bridge (Colonia Venero Claro) or a bedrock outcrop (Critical; Figure 2). Besides, a TDR system for measuring soil moisture was installed between September 2007 and April Available data Hydrological data - Pluviographs: from April 2004 until present. - Hydrographs: from April 2004 until present. Incomplete data record Digital cartography - Topographic map (E: 1/10,000) - Digital Elevation Model (spatial resolution 10x10 m) - Digital ortophotos - Land use and vegetation map (E: 1/50,000) - Geological map (E: 1/50,000) - Geomorphological and surficial deposits map (E: 1/50,000) - Detailed topographic map of one reach of the Arroyo Cabrera (E: 1:500) Figure 2. Location of the hydrologic instruments. The Venero Claro flow gage define the outlet of the basin.

Two flow gauges (WL16 Level Water, Global Water) are also installed in two control sections of the Arroyo Cabrera where a concrete-bed bridge (Colonia Venero Claro) or a bedrock outcrop (Critical;

4 Implemented and calibrated models: - A hydro-geomechanical model (Dietrich & Montgomery 1998) enabled an estimation of the critical rainfall threshold that triggered the 1997 event. An analysis of slope stability was applied, based on the concept of infinite slope (Skempton & DeLory 1957). - A hydrological precipitation run-off model, using HEC-GeoHMS (USACE 2003) and HEC-HMS (USACE 2001) computer applications, was used with the aim of simulating and calibrating the hydrological response of the basin. - A hydraulic model using the critical-depth method (Chow 1959, Jarret 1987, O Connor & Costa 1993) to determine the peak flow running through the Arroyo Cabrera as a result of the debris flood of December 18, Other available data: - Bulk density of soil samples and soil depth measurements. - Availability of historical cartography from the end of the 19th century - Graphical archive (photographs, sketch maps...) of historical events, and especially of the debris flood of Vertical aerial photographs for stereoscopic vision at scales 1:33,000 ( ), 1:18,000 (1978) y 1:30,000 (1984). Most important research projects carried out in the Arroyo Cabrera test site Generation of mass movement hazard maps by using GIS techniques in two sectors of the Sierra de Gredos (Spanish Central System) (REN ). National Programme of Natural Resources, Spanish Interministerial Commission of Science and Technology (CICYT). Main researcher: Javier de Pedraza Gilsanz. October 1, September 30, Team: 6 researchers. Budget: 59,570 euros Incorporación de innovaciones metodológicas al análisis del riesgo de inundaciones, financiado por la UCLM a través de las Ayudas para Proyectos de Profesores Contratados a Tiempo Completo (Clave orgánica ). Investigador principal: Andrés Díez. Otros investigadores: Javier Lario, José Francisco Martín-Duque y Gerardo Benito. Dotación económica: euros Incorporation of geological methods to the analysis of hazard from catastrophic floods (GEORIADA), funded by the Spanish Geological Survey. Main researcher: Andrés Díez Herrero. October 19, 2005-October 19, Team: 9 researchers. Budget: 70,034 euros

- A hydrological precipitation run-off model, using HEC-GeoHMS (USACE 2003) and HEC-HMS (USACE 2001) computer applications, was used with the aim of simulating and calibrating the hydrological

5 Mejoras en la estimación de la frecuencia y la magnitud de avenidas torrenciales mediante análisis dendrogeomorfológicos (CLG /HID) del Programa Nacional de Biodiversidad, Ciencias de la Tierra y Cambio Global (Plan Nacional de I+D+I ), Comisión Interministerial de Ciencia y Tecnología (CICYT). Investigador principal: Andrés Díez. Equipo: 9 investigadores (8 investigadores + 1 becario). Dotación económica: euros Métodos Avanzados para el estudio Dendrogeomorfológico de Avenidas torrenciales y sus riesgos asociados (CLG ) del Programa Nacional de Biodiversidad, Ciencias de la Tierra y Cambio Global (Plan Nacional de I+D+I ), Comisión Interministerial de Ciencia y Tecnología (CICYT). Investigador principal: Andrés Díez. Equipo: 12 investigadores. Dotación económica: euros. Potential End-users - Civil Protection Unit of Avila (Spanish Ministry of Interior), Subdelegation of the Spanish Government to Avila. - Environmental Land Service of Castilla and León Regional Government, Territorial Delegation to Avila. - Tagus Water Authority (Spanish Environment Ministry).

Equipo: 9 investigadores (8 investigadores + 1 becario). Dotación económica: 54.000 euros.

Flash Flood Science. Chapter 2. What Is in This Chapter? Flash Flood Processes

Flash Flood Science. Chapter 2. What Is in This Chapter? Flash Flood Processes Chapter 2 Flash Flood Science A flash flood is generally defined as a rapid onset flood of short duration with a relatively high peak discharge (World Meteorological Organization). The American Meteorological