Water hazard refers to the endangerment of an area by water, regardless of whether the hazard originates from water bodies or artificial water accumulations (flooding, ice drift) or is caused by other events (e.g. cloudburst, rupture of water reservoirs).
If immediate precautions become necessary to avert an emerging water hazard, the neighbouring municipalities, even if they are not threatened, are obliged under § 52 Abs. 1 of the Hessian Water Act (HWG) to provide the necessary assistance if this can be done without significant disadvantages of their own. The municipality obliged under this obligation must act on its own initiative as soon as it recognises the water hazard - at the latest at the request for help from the threatened municipality - and not only on the order of the water authority. If a dike is endangered in the event of flooding, the inhabitants of the threatened and, if necessary, neighbouring municipalities must provide the necessary assistance by personal services or other services by order of the water authority pursuant to § 52 Abs. 2 HWG within the framework of the conventional.
Where necessary, the water authorities shall set up flood warning and reporting services in surface waters in order to warn the locally competent authorities in good time of expected flooding, § 53 para. 1 HWG. According to § 53 Abs. 2 HWG, municipalities which, according to experience, are endangered by floods must set up a water defence service which implements measures to avert danger.
In the event of an imminent danger and in the event of a dike breach on Rhine and Main winter, the water authority is authorised under § 53 para. 4 HWG to order operations of the units and institutions of civil protection (§ 26 HBKG) until the disaster has been determined in accordance with § 43 HBKG. The obligation to pay costs and reimbursement of costs in the event of an operation by the fire brigades are governed by §§ 60 and 61 HBKG.