The monitoring of urban development has a special role to play in the search for environmental sustainability at the local level. It may enable the assessment of policies and planning strategies as well as the improvement of accountability and effectiveness in urban governance. When urban planning has to articulate sustainability objectives, both internally, within urban areas, and externally, when there are nearby natural areas, monitoring may reveal itself to be of increased relevance. This paper critically analyses local plan evaluation in Portugal in the light of the current theoretical debate on monitoring urban development control. A focus is given to the role and requisites of such evaluation, as well as the prediction of likely challenges during its implementation in the Portuguese context. The case study is centred on the urban master plan and associated implementation reports of the Municipality of Aveiro, close to a littoral wetland area, which constitute, so far, unique examples of a local planning monitoring process in Portugal.