Abruzzi, also called Abruzzo, regione, central Italy, fronting the Adriatic Sea and comprising the provincie of L’Aquila, Chieti, Pescara, and Teramo. Most of the region is mountainous or hilly, except for such intermontane basins as those of L’Aquila, Sulmona, and Fucino. The Apennines, the dominant physical feature, consist of three chains trending northwest-southeast, of which the easternmost, including the Gran Sasso d’Italia (9,560 feet [2,914 m]) and Maiella groups, is the highest. From the Gran Sasso, sand and clay hills present a gradual slope eastward to the narrow Adriatic shoreline. The few small coastal harbours have little economic importance for fishing or commerce. The principal rivers (the Tronto, Pescara, Sangro, and Trigno) drain to the Adriatic, providing irrigation in their lower courses. The course of these streams is irregular, and, because of massive deforestation on the upper slopes, floods and landslides occur frequently during the spring and fall rains.