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Rainfall-induced sediment disasters during hurricane incidence in Nuevo Leon, Mexico
1)1)

Laura Sanchez-Castillo, 2) Tetsuya Kubota, and 3) Israel Cantú-Silva

Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University,University,

3)

2)

Faculty of Agriculture, Kyushu

Faculty of Forestry Sciences, Universidad Autonoma de Nuevo León, Mexico

Introduction
The consequences of rainfall-induced sediment related disasters in areas where meteorological events such as cyclones,
hurricanes or typhoons are recurrent are ravaged. Throughout its history, the state of Nuevo Leon have been hit by major
tropical storms and hurricanes in summer and part of fall developed in the Atlantic and Caribbean sea, reaching the gulf ofMexico coast affecting all the state. From the years of 1851 to 2011 the frequency of tropical storms and hurricanes appears toincrease, especially from 2000 to 2010. This increasing in the frequency of hurricanes has led to an increase of the number oflandslides occurred in the area of the state of Nuevo Leon. Although there is not a complete landslide database in Mexico,
preliminary statistics show that most catastrophic sediment related disasters have been associated with rainfall.

Study Area
The state of Nuevo Leon is located in the northeast part of Mexico; its territory covers 64,220 square kilometers. The Sierra
Madre Oriental, one of Mexico‘s major mountain ranges, crosses the state (Figure 1). Nuevo León has an extreme climate, andthere is very little rainfall throughout the year. The average annual rainfall is between 300 and 600 mm. Due to the extreme
climate of the state of Nuevo Leon and the presence of hydro meteorological phenomena like hurricanes and drought thepresence and spread of forest fires are promoted. Also the lack of regulations in the Sierra Madre Oriental area makes theimmoderate logging and overgrazing that are huge problems for this area of the state, which is affecting the vegetation
coverage and causing erosion problems. In recent years, the urban sprawl has spread to the Sierra Madre Oriental Area, theconstruction of houses, buildings and roads had change the natural topography of the area affecting the hydrology. Even withall these risks, some of these buildings are raised without considering the consequences of the steep terrain and runoff waterrunning down the slopes in the rainy season, and even more of the ones when hurricane strikes the metropolitan area.

Figure 1. The state of Nuevo Leon in Mexico and Sierra Madre Oriental

Methodology
Historical Information of the incidence of hurricanes and severe storms that impacted Nuevo Leon state from the year of1971 to 2010 was gathered and analyzed along with the total accumulated rainfall during each incidence in two different
meteorological stations in Nuevo Leon state; these are to establish the pattern of accumulated rainfall during each hurricane
event during this period of time. Rainfall data from two different stations was analyzed: Station 1 and 2 respectively. Station 1is located in southern part the Sierra Madre Oriental and the Station 2 in the metropolitan area of the capital of Nuevo Leonstate: Monterrey city. The rainfall data from these meteorological station was obtained from the SMN (Meteorological National
Service of Mexico), and the described meteorological stations above were chosen because their proximity to severe sedimentdisasters in the state of Nuevo Leon. Sediment disasters information was obtained from the records from Civil Protection of
Nuevo Leon and historical records from the local newspapers.

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Results
A total of nine hurricane events that impacted Nuevo Leon state from the period of 1971 -2010 were analyzed.
During the occurrence of hurricane Alex in 2010 the number of landslides that occurred just in themetropolitan area of Monterrey city was counted as 13. The section of 843.65 Km length in roads weredamaged, the bridges and drainage system in the metropolitan area adjacent to the Sierra Madre Oriental
were destroyed, a total of 3,340 million of Mexican pesos were invested in the reconstruction of infrastructuredamages from hurricane Alex (Figure 2). The daily accumulated rainfall during each hurricane event in Nuevo
Leon state from the years of 1971-2010, showed an increasing tendency in the rainfall intensity during eachhurricane event (Figure 3). The increasing tendency in rainfall intensity came along with an increasing
number and severity of sediment disasters during hurricane events in the Metropolitan Area of Monterrey cityand Sierra Madre Oriental (Figure 4).

A)

B)

Figure 2.

A) Sediment related disasters in the Metropolitan Area, and B) Mountainous Area of NL state    Figure 3. Accumulated Rainfall during each  Figure 4. Longterm fluctuation of landslide frequency

hurricane event in NL state.

duringhurricane

eventsinMetropolitan

andMontainous area of NL state.

Conclusion
Between the period of 1971-2010 the hurricane event which brought the highest cumulative rainfall was Alex with 862 mm.
All the hurricane events and severe storms analyzed shown an accumulated rainfall bigger than the minimum average annual
rainfall in the state of Nuevo Leon, also every event analyzed in this study caused several infrastructure and facilities damages,
citizen casualties and several landslides in the state of Nuevo Leon. The lack of a precise landslide inventory and historical
records of the landslides registered in the state of Nuevo Leon, deduces a big problem to solve for the development of aaccurate warning system in this northeast area of the country of Mexico.

References
Sanchez-Castillo L, Kubota T, Cantu-Silva I (2012): Hurricane Incidence and Sediment disasters under the climate change inNuevo Leon, Mexico. Proc. 3rd Conference on Forest and Water in a Changing Environment, R.

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