Small harbours risks: Lowering for fishery and increasing erosion. The case of Portinho da Aguda (Nw Portugal) H. Granja, L. Bastos, J. Pinho, J. Gonçalves, R. Henriques, A. Bio and A. Magalhães Published online: 09 May 2011 DOI: 10.1051/litt/201109003